Pinion Angle & FFMetal Battery Box Issue - FFCars.com : Factory Five Racing Discussion Forum

 
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post #1 of 26 (permalink) Old 05-19-2017, 12:17 AM Thread Starter
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Pinion Angle & FFMetal Battery Box Issue


I have been in the Go-Kart phase now for a few months. After setting ride height and with axle loaded on jack stands, an unexpected issue occurred while trying to set the pinion angle.

Not able to set proper pinion angle of 1-2 degrees down due to the differential cover hitting the sunken FFMetal battery box.

Has anyone else had this issue?

Pertinent Information:
1) Early Mk IV Complete Kit (so rear lower-trunk configuration is not flat)
2) 3-Link, Solid 8.8 Axle from FFR with pre-welded banana for upper link
3) Levy 408W engine and his beefed up T5 Tranny
4) Solid Engine Mounts from Late Model Restoration for Fox Body convertibles. Gordon Levy recommended these to sit the engine lower and to better stabilize the high torque engine.
5) Standard Energy Suspension Tranny Mount.
6) Engine and Tranny essentially parallel with frame (no sig upward or downward slope compared to frame rails)
7) Ride Height set at 4 inches Front and 4.5 inches Rear.
8) FFMetal Battery Box sunken in the truck
9) 15 inch wheels


At first, I thought I was using the digital angle finder incorrectly, but it has a relative angle mode making the calculation fairly simple. Also, I am fairly certain, I am not trying to set the pinion 1-2 degrees up (as opposed to down). Also, I am following Jeff Kline's method to measure the angle which seems simple enough: 1) set ride height 2) Car up on jack stands with axle loaded on jack stands 3) Taking angle measurement off the crank pulley and pinion flange face with drive shaft off 4) Then calculating the difference.

With the car on Jack stands and the axle loaded as described above, looking at the length of the car from the driver side the crank shaft and therefore trans output is angled, rotated, or sloped in a clockwise fashion 1.3 degrees. Of interest the main frame tubes are sloped in the same directions 1.2 degrees. By just eye balling the pinion it ended up being angled, rotated, or sloped 3 degrees in a counter clockwise direction. Resulting in a relative angle at the pinion of 4.3 degrees downward. Meaning I need to rotate the pinion and pumpkin up or clockwise to achieve a relative angle of 1-2 degrees downward. But as I reach close to the 2 degree objective the differential cover hits the front surface of the FFMetal battery box. Bummer!

The pictures below may or may not help. Pictures left to right: FFMetal Battery Box, Differential Cover Clearance at relative 4.3 degrees down and you can see how close it is already to the front of the battery box, Trans Mount x 2, and Solid Engine Mounts

To the best of my knowledge, I have the rear suspension put together properly. And the battery box is in the right positions and to the rear as much as possible.


I only see two options: 1) Put shims under the trans at the mount to raise it, or 2) Scrape the sunken battery box.

Any thoughts?

Attached Images
File Type: jpg BatBox.jpg (16.2 KB, 86 views)
File Type: jpg DiffCl.jpg (8.4 KB, 86 views)
File Type: jpg TransMt.jpg (13.2 KB, 74 views)
File Type: jpg TransSup.jpg (17.9 KB, 71 views)
File Type: jpg EngMt.jpg (14.0 KB, 68 views)
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post #2 of 26 (permalink) Old 05-19-2017, 01:03 AM
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The FFMetals drop battery box needs to be pushed to the drivers side of the car for ALL solid axle installs to allow the axle to articulate. You can place it in the center, as you have it shown, ONLY when you have Independent Rear Suspension.


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post #3 of 26 (permalink) Old 05-19-2017, 01:09 AM
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would a factory Ford stamped steel diff cover offer more clearance?
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post #4 of 26 (permalink) Old 05-19-2017, 05:22 AM
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Racing Girdle

I had the exact same issue with my battery box. The problem is with your racing girdle. The battery box was designed to fit when using the standard stamped steel differential cover. There are some racing girdles that may clear but mine clearly had contact interference issues. I ended up modifying my battery box which now requires a smaller battery. If I had to do it again I would give up the girdle or find one that fits without modifying the battery box. There is only one battery that fits my box and I sometimes wonder if that was a wise choice.




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File Type: jpg Battery Box.jpg (241.4 KB, 169 views)
File Type: jpg Battery Box _ a.jpg (189.9 KB, 166 views)


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post #5 of 26 (permalink) Old 05-19-2017, 12:17 PM
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How about moving the rear axle forward maybe 3/8 inch? Shorten the LCAs by 3/8 or drill new holes in the axle adapter brackets? The latter would be easiest. You could either weld up existing hole and re-drill or drill a new hole between the two existing holes but 3/8 to the rear. Check that your drive shaft can go 3/8 further into the trans first.

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post #6 of 26 (permalink) Old 05-19-2017, 01:10 PM
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Or as Frank suggested, move the box as far to the driver's side as possible. I had FFMetal's box in my roadster and in my coupe. Centered with the IRS in the roadster, to the left with the 3-link in my coupe. Not even close to the differential in the coupe.
Sounds a lot easier than moving the axle, cutting the LCA's, unless you like fabricating.

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post #7 of 26 (permalink) Old 05-19-2017, 01:30 PM
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Quote:
Originally Posted by CraigS View Post
How about moving the rear axle forward maybe 3/8 inch? Shorten the LCAs by 3/8 or drill new holes in the axle adapter brackets? The latter would be easiest. You could either weld up existing hole and re-drill or drill a new hole between the two existing holes but 3/8 to the rear. Check that your drive shaft can go 3/8 further into the trans first.
??? Doing that would really effect how the wheels would look in the rear wheel wells, and a lot of work. Just try a 1/2" spacer under the tranny, that may give you enough clearance. Put a stack of washers there just to measure.
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post #8 of 26 (permalink) Old 05-19-2017, 01:49 PM
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Battery Box

I think he is already as far to the left as possible on the Mk4. Here is what mine looks like installed per the instructions. I think you could probably go another inch or so but after that you would have to modify the frame structure. You might consider a lower profile cover. I would call around and see what is available. I believe this one might allow for more clearance but you would have to verify. On another note, there probably is no real benefit to a girdle cover on our cars.

http://www.cjponyparts.com/different...5-2012/p/RDC2/



Quote:
Originally Posted by frankeeski View Post
The FFMetals drop battery box needs to be pushed to the drivers side of the car for ALL solid axle installs to allow the axle to articulate. You can place it in the center, as you have it shown, ONLY when you have Independent Rear Suspension.


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post #9 of 26 (permalink) Old 05-19-2017, 02:46 PM
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How much interference is there?

If that cover has enough meat on it, could you have the cover machined just a bit in the area where it hits the box to get some clearance?

I doubt you really need that beefy of a cover. If you were going to put slicks on the car and hit the dragstrip all the time, then I could see a need...but on regular road surfaces with vintage Avon tires, I don't think you'd get enough traction to rip the differential housing apart.

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post #10 of 26 (permalink) Old 05-19-2017, 02:52 PM Thread Starter
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The battery box is to the driver. See pictures below that give a better perspective. In the second picture, the blue towel is sitting over the box. As stated, at most it could go another 2 inches to the driver side, but that still does not solve the problem. The differential would still hit.

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File Type: jpg BatBox3.jpg (19.1 KB, 44 views)
File Type: jpg BatBox1.jpg (23.7 KB, 43 views)

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post #11 of 26 (permalink) Old 05-19-2017, 03:01 PM Thread Starter
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Quote:
Originally Posted by brian1967 View Post
would a factory Ford stamped steel diff cover offer more clearance?
I had the same thought of the "beefy" differential cover being not needed and going back to the original steel cover that came with axle. But as it turns out it only buys me 1/8 of a inch in clearance. The original steel plate bulges out on the driver side half of the plate a lot. I also looked at Summit Racing to see what other options might be available, but it was difficult to tell without dimensions. I guess I could call their customer service.
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post #12 of 26 (permalink) Old 05-19-2017, 03:16 PM Thread Starter
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Quote:
Originally Posted by CraigS View Post
How about moving the rear axle forward maybe 3/8 inch? Shorten the LCAs by 3/8 or drill new holes in the axle adapter brackets? The latter would be easiest. You could either weld up existing hole and re-drill or drill a new hole between the two existing holes but 3/8 to the rear. Check that your drive shaft can go 3/8 further into the trans first.
My son, the mechanical engineer, had the same thought, particularly since I am planning on going with "Breeze's" adjustable rear-lower control arms (along with his duel adjustable shocks and springs). We were wondering how much space we would have in the rear wheel wells once the body was on, would we be able to move the axle forward enough without rubbing the body. The tires on the rear are 295/50/15.

He did not like the idea of shimming up the trans, although he agrees it would provide space and may allow the proper pinion angle; he feels it compromises the drive shaft angle some. However it is a simple thing to mock up and see how it looks.

The other thought both of us had was, if we scrapped the sunken battery box, it opened the possibility for the 5-link suspension set up in the future.
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post #13 of 26 (permalink) Old 05-19-2017, 03:21 PM Thread Starter
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Quote:
Originally Posted by Dan Babb View Post
How much interference is there?

If that cover has enough meat on it, could you have the cover machined just a bit in the area where it hits the box to get some clearance?

I doubt you really need that beefy of a cover. If you were going to put slicks on the car and hit the dragstrip all the time, then I could see a need...but on regular road surfaces with vintage Avon tires, I don't think you'd get enough traction to rip the differential housing apart.
Dan,

With the current set up, the differential cover actually hits the battery box close to but before obtaining 2 degree downward pinion angle. And then, under force the pumpkin should rotate further back or clockwise (looking at the side of the car from the driver side).
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post #14 of 26 (permalink) Old 05-19-2017, 03:59 PM
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You're trying to point the nose of the axle up...right?

I believe if the rear of your transmission is pointing down (relative to the crankshaft damper), then you want the front of the pinion pointing up.

Like the attached picture.
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File Type: jpg driveline-angle-set-up-diagram.jpg (122.5 KB, 40 views)

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post #15 of 26 (permalink) Old 05-19-2017, 05:05 PM
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Quote:
Originally Posted by Zman View Post
My son, the mechanical engineer, had the same thought, particularly since I am planning on going with "Breeze's" adjustable rear-lower control arms (along with his duel adjustable shocks and springs). We were wondering how much space we would have in the rear wheel wells once the body was on, would we be able to move the axle forward enough without rubbing the body. The tires on the rear are 295/50/15.

He did not like the idea of shimming up the trans, although he agrees it would provide space and may allow the proper pinion angle; he feels it compromises the drive shaft angle some. However it is a simple thing to mock up and see how it looks.

The other thought both of us had was, if we scrapped the sunken battery box, it opened the possibility for the 5-link suspension set up in the future.
Lets talk trans shim. Although it will affect the pinion angle, the trans mount/shim also sets the drive shaft angle. My procedure: 1-I like to settle on a ride height first. 2-I shim the trans so the front of the driveshaft is slightly ( maybe 3/8?) inch higher than the rear of the shaft. I do this because I have more axle up/bump travel than droop travel. The goal is to make sure the u-joints don't bind at either end of axle movement. 3-Then I set pinion angle. Sorry I missed that your trans has no shim in your pictures. It is VERY common to shim the trans usually somewhere around 1/2 to 3/4 inch. This could very well be your solution. Remember, the ideal driveline has the trans output shaft parallel to the pinion shaft. They can be offset quite a bit either in side view or top view but they need to be parallel. The common 2 deg down pinion angle is only there so that under max accel, as things move a bit, the actual angle becomes zero. W/ a 3 link w/ rod ends in all the links I could make a pretty good argument to reduce it to 1/2 deg. BTW, the Breeze DA shocks are fantastic. BTW2, it's been a long time since I had 295-15 tires so I can't be absolutely sure but think you will be fine on the body clearance. Note that the MkIV has a lot of space ahead of the rear wheel in side view.
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post #16 of 26 (permalink) Old 05-19-2017, 05:30 PM Thread Starter
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Quote:
Originally Posted by Dan Babb View Post
You're trying to point the nose of the axle up...right?

I believe if the rear of your transmission is pointing down (relative to the crankshaft damper), then you want the front of the pinion pointing up.

Like the attached picture.
Yes, trying to point it up, and that in lies the problem with the clearance. I can point it down more without any issue.
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post #17 of 26 (permalink) Old 05-19-2017, 05:35 PM Thread Starter
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Quote:
Originally Posted by CraigS View Post
Lets talk trans shim. Although it will affect the pinion angle, the trans mount/shim also sets the drive shaft angle. My procedure: 1-I like to settle on a ride height first. 2-I shim the trans so the front of the driveshaft is slightly ( maybe 3/8?) inch higher than the rear of the shaft. I do this because I have more axle up/bump travel than droop travel. The goal is to make sure the u-joints don't bind at either end of axle movement. 3-Then I set pinion angle. Sorry I missed that your trans has no shim in your pictures. It is VERY common to shim the trans usually somewhere around 1/2 to 3/4 inch. This could very well be your solution. Remember, the ideal driveline has the trans output shaft parallel to the pinion shaft. They can be offset quite a bit either in side view or top view but they need to be parallel. The common 2 deg down pinion angle is only there so that under max accel, as things move a bit, the actual angle becomes zero. W/ a 3 link w/ rod ends in all the links I could make a pretty good argument to reduce it to 1/2 deg. BTW, the Breeze DA shocks are fantastic. BTW2, it's been a long time since I had 295-15 tires so I can't be absolutely sure but think you will be fine on the body clearance. Note that the MkIV has a lot of space ahead of the rear wheel in side view.
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Trans Shim may be the way to go for now, since that is normal for these cars. Adding adjusting rear-LCA's and DA shocks later may further improve the clearance issue along with handling.
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post #18 of 26 (permalink) Old 05-19-2017, 05:42 PM Thread Starter
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Here are 2 pics of the original diff cover. The 2 notches go towards the ground. It does not, in reality, provide much more clearance. As I mentioned, about 1/8 of an inch, due to its shape.
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File Type: jpg OldDiff2.jpg (15.3 KB, 40 views)
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post #19 of 26 (permalink) Old 05-19-2017, 06:22 PM
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I have the FF Metals box and a 3 link. I also happen to have my car jacked up right now. You should not have any clearance issues with a stamped cover. I just took mine off with the axle at full droop. I didn't have to move anything. I have a VPM swaybar, but the panhard bar is actually the closest thing.

I can see that a girdle would not fit. I have always wondered at what point they are really needed. Truth is, most people install them because of the "cool" factor. That being said, I have 500 HP and have my axles out due to a leaking seal and I am chasing a throttle lift vibration.

Shortening the wheelbase would be a pretty big price to pay for a part of questionable function, and zero aesthetics, since you can't see it. If you just have to have it, I would do something with the battery box location.

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post #20 of 26 (permalink) Old 05-19-2017, 06:30 PM
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Excuse the quick hijack.

CaigS,

My transmission is 2* down (1/2" shim) and my pinion is 2* up. So I am parallel. Are you saying that I should be 2* down and 0*? I autocross, so do some hard launches.

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post #21 of 26 (permalink) Old 05-19-2017, 06:55 PM
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There are many pinion angle threads between the two forums. I especially like this one because he defines the "up" and "down" that is always so confusing when describing the angles and problems.

Driveline Setup (aka, Pinion Angle))

To do a search, I use the google format of "site:http://thefactoryfiveforum.com pinion angle" , or "site:http://ffcars.com driveline setup" , or whatever search terms you want. That way it only searches that site, not the whole internet.

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post #22 of 26 (permalink) Old 05-19-2017, 09:35 PM
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Avalanche, Dan, and anyone else who missed it the first half dozen times I posted...

When we talk about pinion angle we are speaking of it relative to the transmission output shaft. If you have the gauge on the driveshaft you are looking at driveline angle, not pinion angle. The driveline angle is not part of the pinion angle equation. When determining pinion angle you can leave the driveshaft on the workbench, and in fact if you follow my method described below it will be easier if you do just that.

Don't get caught up or confused on any thoughts of horizontal or having the chassis level because what we are measuring is not related to the earth or the chassis, only the transmission output and pinion shaft. You could take the measurements with the car standing on it's nose. Think of it this way; when looking at the car from the side if you were to project one line from the transmission output forward and another line from the pinion shaft forward with your pinion angle at zero they would be parallel. If you put any angle to the pinion the two lines are not parallel and would get farther apart as they go forward. If the pinion were to be angled UP (relative to the trans) it's line would be above the output line; if it were angled DOWN the pinion line would be below. Below is what we're after.

My method for ease of measurement:
Set ride height then put the car on jackstands so that the axle is loaded. We don't care if the frame is dead nuts level; we're only going to look at the difference between output shaft & pinion. We know that the crankshaft and trans output shaft are parallel therefore the face of the damper/ crank pulley is perpendicular to the output. We also know that the pinion flange face is perpendicular to the pinion. See where I'm heading? For me it is easier to get a good measurement with the magnetic angle finder by reading vertically on the crank pulley/ damper and pinion flange rather than trying to work with the horizontal shafts themselves. Once you can see the two angles you can then calculate the difference. Generally with these cars we want the front of the pinion down ~1-2 degrees (once again, meaning the input is pointing down in relation to the transmission output shaft). Reason being is so that when the axle tries to rotate it's input upward under acceleration the pinion angle becomes less. This rotation is especially more pronounced on a 4 link car using the soft rubber bushings in OEM Mustang arms vs. a 4 link car with poly bushings or a 3 link with polys in the lowers and the solid upper link.

Three link adjustment is easy; simply alter the length of the upper link---make it longer and the front of the pinion moves upward and vice versa.

Hope that all makes sense and good luck!

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post #23 of 26 (permalink) Old 05-20-2017, 05:09 AM
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Quote:
Originally Posted by CDXXVII View Post
I think he is already as far to the left as possible on the Mk4. Here is what mine looks like installed per the instructions. I think you could probably go another inch or so but after that you would have to modify the frame structure. You might consider a lower profile cover. I would call around and see what is available. I believe this one might allow for more clearance but you would have to verify. On another note, there probably is no real benefit to a girdle cover on our cars.

http://www.cjponyparts.com/different...5-2012/p/RDC2/

Marcel is right........to a point. It all comes down to this when you are making custom mods to one of these cars. The old expression; " In order to make an omelette, you have to break a couple of eggs". The best fix long and short term, is probably to cut the structure of the trunk framing, move the battery box over to the far left and weld in some new supports for structure. I went a completely different route and placed a small footprint battery in the rear drivers fender well.




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post #24 of 26 (permalink) Old 05-20-2017, 06:43 PM Thread Starter
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Quote:
Originally Posted by CraigS View Post
Lets talk trans shim. Although it will affect the pinion angle, the trans mount/shim also sets the drive shaft angle. My procedure: 1-I like to settle on a ride height first. 2-I shim the trans so the front of the driveshaft is slightly ( maybe 3/8?) inch higher than the rear of the shaft. I do this because I have more axle up/bump travel than droop travel. The goal is to make sure the u-joints don't bind at either end of axle movement. 3-Then I set pinion angle. Sorry I missed that your trans has no shim in your pictures. It is VERY common to shim the trans usually somewhere around 1/2 to 3/4 inch. This could very well be your solution. Remember, the ideal driveline has the trans output shaft parallel to the pinion shaft. They can be offset quite a bit either in side view or top view but they need to be parallel. The common 2 deg down pinion angle is only there so that under max accel, as things move a bit, the actual angle becomes zero. W/ a 3 link w/ rod ends in all the links I could make a pretty good argument to reduce it to 1/2 deg. BTW, the Breeze DA shocks are fantastic. BTW2, it's been a long time since I had 295-15 tires so I can't be absolutely sure but think you will be fine on the body clearance. Note that the MkIV has a lot of space ahead of the rear wheel in side view.
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Always glad to see Jeff chime in but I was disappointed he did not have an opinion on my predicament.


I am going to take more precise measurements, but just eyeballing it, it looks like the front of the driveshaft is already about 1/2 inches higher then the rear of the shaft. In that case adding shims to the trans would raise the front of the driveshaft even more. But since my pinion input is pointed down too much because the pumpkin hits the back of the battery box, by adding shims I will be able to rotate the pinion input up or clockwise, so the front of the driveshaft height compared to the rear of the drive shaft may not change that much.

Clearly, the goal is to have the trans output close to parallel (1-2 degrees down/pinion input down). And close to parallel is the key factor, in preventing undue stress or vibration in the driveline. But at some point the 2 parallel lines can be so far apart the driveshaft will either bind or hit the frame.

One of the setups that is somewhat unique to my build is the solid engine mounts that set the engine closer to the ground. It dose provide more space for the higher deck height of the 351W based 408W as well as lowering the engine center of gravity. Gordon Levy who built my engine felt strongly about the need for these mounts. I am not sure if this is playing a role. I think not because as I mentioned originally, as the car is currently Jack up, the crank input shaft is 1.3 degrees slope downward or rotated 1.3 degrees clockwise as viewed from the driver side of the car, and the frame of the car is 1.2 degrees in the same downward slope or clockwise rotation. Meaning the Crank shaft and trans output relative to the frame is only 0.1 degrees down relative to the frame. Essentially the engine and frame are parallel, which seems to be something you would want? Maybe that is not important?


Either way, it is simple enough to shim up the trans and see if it provides enough clearance between the pumpkin diff cover and sunken battery box without creating too much of an extreme angle on the driveshaft.

For now that is less involved than moving than moving the battery or changing the diff cover.

But I must say that based on my measurements the steel original diff cover still will not clear the battery box as things currently are. There is only a 1/8 inch difference in thickness between the 2 covers.

Last edited by Zman; 05-20-2017 at 06:52 PM.
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post #25 of 26 (permalink) Old 05-20-2017, 07:08 PM
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Having your engine lower than some actually helps your situation. That way the pinion can be lower too which rotates the diff away from the battery box.
If you already have the front of the shaft 1/2 in higher than the rear, you may not be able to move it further but a stack of washers is an easy experiment. In this case, as you shim the trans higher, the u-joint binding may occur w/ the axle at full droop. So it's easy to ck for binding. Put your jack stands under the frame and let the axle hang. Put it in neutral and spin the wheel by hand. It may not lock up, but, if there is a stiffness at certain points in the rotation, that is the problem.
Another question for you. Do you feel any vibration on hard accel from 15-35 mph? If you don't, I think it's OK to drive it as is. Not that you don't want to keep working toward a solution to getting that ideal pinion angle, but, if it drives fine, drive it.

FFR 5353K, 408W, TKO 500, 2015 IRS w/ 315 gear, Breeze QA1 DA coilovers front and rear, APE hardtop, Forte front swaybar
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post #26 of 26 (permalink) Old 05-21-2017, 07:18 AM Thread Starter
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Quote:
Originally Posted by CraigS View Post
Having your engine lower than some actually helps your situation. That way the pinion can be lower too which rotates the diff away from the battery box.
If you already have the front of the shaft 1/2 in higher than the rear, you may not be able to move it further but a stack of washers is an easy experiment. In this case, as you shim the trans higher, the u-joint binding may occur w/ the axle at full droop. So it's easy to ck for binding. Put your jack stands under the frame and let the axle hang. Put it in neutral and spin the wheel by hand. It may not lock up, but, if there is a stiffness at certain points in the rotation, that is the problem.
Another question for you. Do you feel any vibration on hard accel from 15-35 mph? If you don't, I think it's OK to drive it as is. Not that you don't want to keep working toward a solution to getting that ideal pinion angle, but, if it drives fine, drive it.


Thanks for all your advice. It has helped me develop a game plan.
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