More rear end issues

[shelbyranger]

Well, I found out why my pinion angle was so far off and the rear wheels were moved too far back in the openings. Took a look under the car and the upper link bracket is collapsing on the bottom causing the differential to rotate up.

[mirose]

Not a great pic. I'm not 100% sure what I'm looking at but your description sounds very concerning. Any time you use the term "collapsing" and "differential" in the same sentence it can't be good.

I'll let some of the experts here chime in and watch along with curiosity. I Hope it's nothing serious
Michael.

[shelbyranger]

If you look the 3 link bracket on the axle tube should be straight. You can see its bending and calapsing towards the center.

[AC Bill]

Huh? I can't see how that area got bent sideways like that? It should move latterly with the pumpkin, as that lower leg is directly attached to it.

I could possibly see that happening, is if something struck it hard, or it was used to jack the car up perhaps? Is the banana bracket welded to the axle tube?

What is that other little brace added to it, that angles up and appears to be welded to the side of the pumpkin? I've never seen that before on the three link bracket?

[shelbyranger]

No Nothing hit it. Car has like 4 miles on it other than Dyno time. Very odd but as its bending it's pushing my wheels further back and changing my pinion angle severely

[AC Bill]

You do have that lower banana bracket arm attached to the pumpkin don't you? Not to the frame somewhere? (although I can't even imagine how that could be done..lol)
I can't see other than an external force, how/why that area would bend like that?
I know it's not uncommon for the bolt hole on the 8.8" rear pumpkin to not line up exactly with the lower leg bracket's hole. (Many simply drill a new hole). Now unless someone tried to get the bolt holes lined up, by wacking the bottom of the brace with a hammer..I'm baffled.
Again, is the banana bracket welded to the axle tube?
Did you ever do any hard starts, IE. rev er up and dump the clutch? I wonder if that happened on the dyno? The only time I have ever seen that bracket bend before, is from guys drag racing, with sticky tires, and big HP.
Very strange indeed..

[shelbyranger]

No I didn't bend it to make it fit. I just noticed the rear wheels getting further back after I drove it. There are no impact marks on it either. Looks like its trying to rotate around the tube and it's crushing the bottom portion of the bracket. I drove it hard a couple times in the very few miles but no dumping clutch or anything. Car makes 676rwhp and 661rwtq. Is that why it's bending?

[Joe]

I'm just going to take a guess here and I'm sure others much smarter than I will chime in. I think you may have still been running too much of a pinion angle prior to it bending. I'm thinking due to your high HP, pinion angle being off and running it on the dyno, it bent. By having the high pinion angle maybe there was more leverage which caused it to bend?

I can't remember who has the kit or what it's called, but there is a bolt in solution that will help to stabilize the three link.

In the meantime, I'm afraid you're going to have to drop the rear axle now..

[Joe]

Here you go..

Welding 3-Link Banana Bracket

3 link brace, 3 link parts

3-Link Support Brace Kits

Also, take a look at the frame where the forward point of pinion adjustment bar mounts. Is there any bending there?

[dv/dt]

How much HP are you running? What torque did you tighten the 4 half inch bolts that clamp the banana bracket to the axle tube too? The only thing that normally keeps it from rotating is the clamping force of the banana bracket and the tube that goes forward to the front of the pumpkin.

Seen it a couple of times before, here's one:

Is my 3 link bracket bent?

I came up with the banana bracket brace for exactly this reason (and as an alternative to welding the bracket to the tube) and, as Joe pointed out, VPM sells them.



3-Link - The missing link!

There has also been one case where the banana bracket was welded to the tube and then the axle tube rotated in the axle housing with similar results. That won't happen with the extra link since the loads are passed directly to the housing from the banana bracket.

Bottom of 3 link bent, why?

Cheers, Rod

[shelbyranger]

[QUOTE=dv/dt;2644969]How much HP are you running? What torque did you tighten the 4 half inch bolts that clamp the banana bracket to the axle tube too? The only thing that normally keeps it from rotating is the clamping force of the banana bracket and the tube that goes forward to the front of the pumpkin.

Car made 676rwhp/661rwtq. I torqued all the bolts to the spec in the manual. So More or less I need to pull it out, straighten the banana bracket and get a 3 link brace to prevent this again?

[Joe]

You know... With that kind of HP/TQ, I really would give serious consideration to this.. Maybe you could sell what's left of your 3 link to off-set some of the cost.

LevyRacing 5-Link Rear Suspension

[shelbyranger]

From what I read tho you have to cut out a section of frame in the mk4 chassis and there's lots of welding. I hear it's quite a project on the mk4

[Joe]

Originally Posted by shelbyranger

From what I read tho you have to cut out a section of frame in the mk4 chassis and there's lots of welding. I hear it's quite a project on the mk4

Oh, I wasn't sure which model you had. At this point I would call Gordon Levy and confirm. I thought I previously read that he was working on a bolt in solution for MKIV.

3 link is really the weak link in a high HP set up like yours.

[buildit]

Joe, what website or catalog is that link for "3 Link Support Brace Kits" pointing to?

Thanks!

Originally Posted by Joe

Here you go..

Welding 3-Link Banana Bracket

3 link brace, 3 link parts

3-Link Support Brace Kits

Also, take a look at the frame where the forward point of pinion adjustment bar mounts. Is there any bending there?

[rich grsc]

Originally Posted by buildit

Joe, what website or catalog is that link for "3 Link Support Brace Kits" pointing to?

Thanks!

Thats the VPM site I think. Yes thats it.
http://www.vintageperformancemotorca...3linkbrace.htm

[Joe]

Vintage Performance Motorcars (VPM)

Vintage Performance Motorcars

[mirose]

Originally Posted by shelbyranger

No I did bend it to make it fit.

Um, Hate to say it, but if you bent something that is supposed to be straight to "make it fit" and then put nearly 700 HP against it, I think you might have your answer to why this happened. I think everyone else has pointed to some good solutions, but unfortunately, you are looking at some work to get it fixed. Sorry about this. If you weren't in a deadline situation this might actually be a "fun" challenge, but this one will probably be stressful. Good Luck.

-M

[Joe]

I assumed it was a typo and that he meant to type "did not"..

[shelbyranger]

Yes sorry for typo. I DID NOT bend anything on assembly

[mirose]

Ok, my bad. Just going by what I read. I take it back.

[AC Bill]

Originally Posted by shelbyranger

Car makes 676rwhp and 661rwtq. Is that why it's bending?

Yup,the four link may have been a better build route with those numbers.
That's serious torque and HP for the unmodified 3 link set up.

I think if you get the brace from VPM, and straighten the bracket, and weld it to the tube, you could still be alright, just don't hammer the throttle to hard..

[5.8Cobra]

Looks just like mine did after two years and I only have 652rwhp. The brace that VPM sells should stop that and reveal the next weak link. You really made a banana out of that banana bracket! I swapped out the 3 link which was designed for a max of 300hp for the Levy 5 link. I would think this may be a better solution for you as well given you have that much HP, I dont think I would trust anything other than the Levy 5 link. I am sure Gordon will come up with a solution for the MK4's if he hasnt already. Even if its more work, its worth it in the end for the adjustability and strength. Good Luck with it and keep us posted.

Mike

Heres mine:

[knuclebuster]

Originally Posted by shelbyranger

From what I read tho you have to cut out a section of frame in the mk4 chassis and there's lots of welding. I hear it's quite a project on the mk4

I put the five link in my mk4, not too bad. Yes there is some minor modification and some welding but if you can build this car you can make the necessary modifications to install the 5 link. I would not call it a major modification or fabrication project. The five link may give you the support and strength that you need for the HP that you have. I will be finding out soon how well it works with 540HP.

Todd

[shelbyranger]

Originally Posted by 5.8Cobra

Looks just like mine did after two years and I only have 652rwhp. The brace that VPM sells should stop that and reveal the next weak link. You really made a banana out of that banana bracket! I swapped out the 3 link which was designed for a max of 300hp for the Levy 5 link. I would think this may be a better solution for you as well given you have that much HP, I dont think I would trust anything other than the Levy 5 link. I am sure Gordon will come up with a solution for the MK4's if he hasnt already. Even if its more work, its worth it in the end for the adjustability and strength. Good Luck with it and keep us posted.

Mike

Heres mine:

That's exactly what mines doing. Except mines doing it with only 4 miles on the car.

[Dan Babb]

Just throwing this out there as a question:

If the metal has started to bend, would you be better off starting with a fresh bracket? Could the fatigue from the bending make it more likely to bend again?

Just wondering if stressed metal is more likely to be a future weak link.

That's a lot of HP and might not be what FFR designed the kit to handle.

[Erik W. Treves]

not saying that this isn't the cause....but I have over 8000 miles on my setup and mine is still straight... I did add a redundant bar from the 3-link bracket on the frame to prevent the mount from getting ripped off the frame...you might check that as well... did the banana bracket rotate on the axle tube?

[5.8Cobra]

If you compare the two pictures you can see that the collar that goes around the axle is twice as wide on mine. This was one of the early 3 link kits that encompassed the vent tube. FFR had so many complaints about fit that they narrowed the bracket. Now stock motored cars can spin that bracket. So with the HP youre making, it didnt stand a chance!
Mine bent but only just so far, you could probably get away with just getting the brace from VPM. Just check your clearance from the banana bracket to the diagonal brace behind it, I bet youre getting close judging by how far swayed over your bracekt is.

Mike

[shelbyranger]

Yes looks like the tack welds broke loose and it rotated alittle bit

[Erik W. Treves]

So the axle tube is rotating in the pumpkin housing? Ah... I welded mine... not sure the 5-link would have helped that... There is a long history of the 8.8 axle tubes breaking the tacks on the pumpkin housing... If look through some of the websites and blogs, for high HP tracks applications they weld the axle tubes and add braces from the pumpkin to the end of the axle tubes. I added a 1 inch weld at the 12,6,3,9 o'clock positions and spot welded the banana bracket to the axle tube. If the axle tube has in fact rotated you need to get that investigated first IMO....