2015 Mustang IRS Components. So it begins. - FFCars.com : Factory Five Racing Discussion Forum
 
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post #1 of 30 (permalink) Old 07-07-2015, 10:44 PM Thread Starter
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2015 Mustang IRS Components. So it begins.

As I’ve mentioned in a few threads already, I ordered one of the 20th Anniversary Roadsters. These all will use the new 2015 Mustang IRS components along with a new rear suspension design from Factory Five. My kit is due in August, but I’ve been working to obtain the necessary Mustang center section and knuckles. FF announced they would make these parts available from Ford at an “attractive” price. But as of last week, they are not available and no pricing has been announced. At the recommendation of FF, I started looking for the parts in salvage. How much wear could 2015 parts have on them, anyway? Since this is all quite new, I thought others would be interested in more details.

What I found is that parts are out there as “zero mile takeoffs” from new Mustangs that leave the factory but then go to an aftermarket assembly line for further performance upgrades. The IRS assembly is on a subframe, and one of the common upgrades with a new more powerful drivetrain is to remove this entire assembly and replace with one that will handle the 600-700 HP engines, bigger and stickier tires, etc. Rather than re-using, these new IRS assemblies are being sold into salvage and are available. Strange IMO, but I’ll take new over used any time. MPS Auto Salvage, a pretty well known source on this forum, has them available.

Last week I called MPS and they had just what I was looking for. A new zero miles assembly, the cast iron case recommended by FF, and the 3.55 ratio I’ve decided to use for my build. They offered the complete assembly to me for $1,350 plus shipping. It left Georgia last Thursday, and Conway called today for delivery. Turns out since my 2-car residential garage doesn’t have a loading dock (!!!) there was going to be an upcharge for a lift-gate delivery on top of the surcharge for a residential delivery. Since they were only 30 minutes or so from my house, I hooked up the SE and picked it up myself. Total shipping was $187. Not too bad for a 415 pound pallet from GA to MI. The IRS assembly was covered with cardboard, strapped to the skid, and everything stretch wrapped. All good. I used my shop crane to pick it out of the back of the trailer and get into the garage.

So here are some pics of the delivered IRS assembly. As best I can tell, it’s exactly what I expected. Everything looks new with no signs of any wear or shipping damage. There is a little surface rust on the cast iron case and the steel hubs, but not unexpected. The case will get a nice shiny coat of POR15 once I take it apart. My next step will be to remove the center section and the knuckles and get them ready for assembly to the new chassis. I've already backed out a number of the mounting bolts, and I was able to get the axle nuts loose. Obviously there will be a ton of parts I don’t need. I’m going to hang onto everything until the kit arrives and I make sure I have what I need. But then I’m hoping to make a few bucks off the unused parts. Seems that some of the parts should have some value, especially the CV axles. The subframe itself is a $900 part, but I’m not sure who might be looking for something like that plus wouldn’t be cheap to ship. No matter what, I think this is a relatively good value for what I received.

As delivered:


Center section waiting to be removed:


Knuckle and hub assemblies, also waiting to be taken apart:




Interesting tag on the rear cover. No mention of friction modifier.

So now I’m up to four parts on hand for the new Roadster build. The IRS, the wind wings and visors I scored for 50% off at the FF Open House, and a new set of Harbor Freight horns. Don’t laugh. They work great and are cheap. I’ll be driving to FF to pick up the new kit hopefully in early August, based on my current production date. Then the fun really begins.


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Last edited by edwardb; 07-08-2015 at 11:50 AM.
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post #2 of 30 (permalink) Old 07-07-2015, 11:19 PM
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Very cool Edward...

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post #3 of 30 (permalink) Old 07-07-2015, 11:27 PM
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Nice! I might consider this for the next build in a 33.
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post #4 of 30 (permalink) Old 07-07-2015, 11:51 PM
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Those are good looking control arms. I wonder if they can be used on the FF build? I wonder if these differentials would be a retrofit to existing kits? I bet with a little head scratching, new control arms could be designed and built to fit these to existing kits and IRS subframes.

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post #5 of 30 (permalink) Old 07-08-2015, 12:06 AM Thread Starter
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Quote:
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Those are good looking control arms. I wonder if they can be used on the FF build? I wonder if these differentials would be a retrofit to existing kits? I bet with a little head scratching, new control arms could be designed and built to fit these to existing kits and IRS subframes. Bob
None of the existing Mustang arms are used in the new FF IRS design. The kit comes with all new arms, adjusters, CV axles, etc. The arrangement is slightly different plus the track is narrower. I can't comment if these parts could be built into existing kits. This is my first experience with IRS so seeing all this for the first time. My two builds to date were solid axles.

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post #6 of 30 (permalink) Old 07-08-2015, 12:56 AM
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2015 Mustang IRS.

Given my kit won't arrive until September, I think I will hold out for a bit to see if FFR is going to be able to supply these units.
Plan running a Mike Forte 306/345hp engine with the T5. Not sure what the ideal rear gears should be looking for.
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post #7 of 30 (permalink) Old 07-08-2015, 01:00 AM
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Thanks Edward

Thanks for the detailed info Edward. I am still in the planning stages of a MK IV build and had already purchased the Lincoln MK VII IRS and had it nearly ready to go. After seeing your assembly I think I will switch to the Mustang IRS. I'm still about a year away from ordering the kit. Thanks again for the info.
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post #8 of 30 (permalink) Old 07-08-2015, 01:01 AM
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Check out Steeda and BMR for some very nice rear suspension parts for the 6G Mustang. Also any parts you dont want or need 2015+ Mustang Forum News Blog (S550 GT, GT350, GT500, I4, V6) – Mustang6G | The Ultimate 6th Generation Mustang (S550) Enthusiast Site. BTW you wont regret the 2015 rear suspension. I have Steeda springs and sways on my 2015 GT with Performance Pack and its on the money.

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post #9 of 30 (permalink) Old 07-08-2015, 01:08 AM
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2015 irs brakes

Hello:
I like that FFR is going to use the 2015 irs.
The new irs brakes from mustang, do they fit 17" wheels, or do they need to be 18"or 19"
Planing future coupe build.
Thanks
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post #10 of 30 (permalink) Old 07-08-2015, 01:18 AM
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Quote:
Originally Posted by dat65 View Post
Hello:
I like that FFR is going to use the 2015 irs.
The new irs brakes from mustang, do they fit 17" wheels, or do they need to be 18"or 19"
Planing future coupe build.
Thanks
I believe a 17" will work out back. IIRC the drag racers are using 17" Race Stars with slicks.


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post #11 of 30 (permalink) Old 07-08-2015, 01:25 AM
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I hope they'll accommodate the 15" pin drive crowd. Nice update. Go get em Edward.

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post #12 of 30 (permalink) Old 07-08-2015, 01:50 AM
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Hi Edward, wow I'm so looking forward to seeing your build thread. I'm so gellous.
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post #13 of 30 (permalink) Old 07-08-2015, 04:04 AM Thread Starter
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Got everything apart already. Wasn't really that hard. Used a three-jaw puller to get the axles out of the hubs. Came off pretty easily. The CV axles popped out of the diff with a little bump from a crow bar, just like they're supposed to. Then took the diff out of the cradle. Will get everything cleaned up and that designer rust orange color of the diff painted gloss black with a POR15 treatment.

Note this picture also shows a pretty big design difference of the 2015 IRS knuckles compared to the older design. You can see the four bolts on the inside holding the bearing carrier in place vs. the pressed in bearings from the past.


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post #14 of 30 (permalink) Old 07-08-2015, 04:14 AM Thread Starter
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Originally Posted by rickscobra View Post
Given my kit won't arrive until September, I think I will hold out for a bit to see if FFR is going to be able to supply these units.
Plan running a Mike Forte 306/345hp engine with the T5. Not sure what the ideal rear gears should be looking for.
I will be interested to see what FFR comes up with. There are a number of factors that go into the final drive ratio decision. Lots of threads and discussion on the subject. But FWIW, for that engine and trans, 3.55 is one of the most common choices.

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post #15 of 30 (permalink) Old 07-08-2015, 11:01 AM
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Nice score, Edward. So, given that the pallet w/ assembly was 415 lbs, that means the assembly by itself is probably around 385 lbs. That's beefy!

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post #16 of 30 (permalink) Old 07-08-2015, 11:12 AM
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edwardb,
Kudos to you for being the pioneer on this! I can't think of anyone who would do a more thorough explanation and documentation of the subject

Jeff

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post #17 of 30 (permalink) Old 07-08-2015, 11:20 AM
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MPS IRS supplier.

I will be giving the MPS folks a call this morning to see if they have a 3:55 center section in stock. Really don't have the experience to say FFR will be able to beat the MPS price and/or availability.

Rick
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post #18 of 30 (permalink) Old 07-08-2015, 08:01 PM Thread Starter
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There was a question on the other forum about ABS, including the sensor and tone rings as compared to the old design. Thought I would share here as well. There is a mounting point on the top of the knuckles for the ABS sensor and cable. The picture below has the sensor in place, showing how it extends into the hub area. Also below is a picture of the CV axle end that plugs into this area. As you can see there are no tone rings. So I did some some searching, and found that wheel bearings with a magnetic ABS pulse generator are now being used in some cars. Looks like that's what Ford did here. The dark ring right under the tip of the ABS sensor in the first pic is magnetic as verified with a small knife blade. Check this video. https://www.youtube.com/watch?v=e32t-d32SEg. Very interesting.



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post #19 of 30 (permalink) Old 07-08-2015, 08:16 PM
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MPS price for Mustang center section.

MSP says they are selling the center sections for $750 at this time. Have one 3:55 on the shelf as of this morning.
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post #20 of 30 (permalink) Old 07-08-2015, 08:20 PM
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In your first set of pictures there is a part that kind of looks like a black dog bone going from the lower link to the top of the knuckle. Any idea what it is. The only thing I can think of is it is there for shipping or maybe some type of anti-sway bar.

Just curious,

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post #21 of 30 (permalink) Old 07-08-2015, 08:40 PM Thread Starter
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Couple more updates

Wrapping up the tear down and preparation for the 2015 Mustang IRS parts. Thought I would share a few more things. Got out the scale and weighed some of the parts. The knuckle and hub assemblies weigh 17 lbs each. The cast iron diff weighs 94 lbs all up. It wasn't easy to get the thing to sit still on the scale, but I think this is quite close. The fact that I can lift it (barely...) says this weight is in the ballpark. Multiple on-line sources cite the aluminum version is 24 lbs lighter, putting it in the 70 lbs range. Looking at some threads about the older design, appear both numbers are slightly heavier than before. But not much. Finally, even though I won't use them, weighed the CV axles. 43 lbs between the two of them. The new design is 34 spline at the diff, and 32 at the hub. Pretty meaty.

I managed to spill some of the fluid out the axle holes while moving it around. I'm just not smelling the quite distinctive odor of friction modifier. But the Ford instructions clearly state 3.2 pints (1.5L) SAE 75W-85 Premium Synthetic Hypoid Gear Lubricant and 4 oz. Motorcraft XL-3 Additive Friction Modifier. I'm planning to drain and replace the fluid as specified. This diff is a standard clutch-pack style limited slip setup. A Torsen setup is available only in the 3.73 ratio.

Several have asked if the internals are the same as past 8.8 diff, e.g. ring and pinion, bearings, etc. I can't answer specifics, but I'm guessing the answer is mostly no. In multiple searches, I found Ford referring to this new IRS diff as a "Super 8.8" touting its strength compared to past versions. I found a side-by-side pic of the new pinion gear compared to the old. The new is larger and longer. The slightly heavier weight compared to the past is also a clue.

Several have commented about the geometry of the new IRS, including the somewhat unusual looking links between the upper and lower pivot points. I compared the pics and knuckles now in hand with the pictures and drawings FF has provided of the new design installed. None of these short links are in the FF design. In fact, clearly one of the pivot points looks like it gets cut off the knuckles, as in the picture below. I won't be cutting anything until the kit and full instructions are on hand. But interesting.


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Last edited by edwardb; 07-08-2015 at 09:50 PM.
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post #22 of 30 (permalink) Old 07-08-2015, 08:42 PM Thread Starter
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Quote:
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In your first set of pictures there is a part that kind of looks like a black dog bone going from the lower link to the top of the knuckle. Any idea what it is. The only thing I can think of is it is there for shipping or maybe some type of anti-sway bar.

Just curious,

Bill Lomenick
Nope, it's not for shipping. Part of the Ford design. The FF design doesn't use this piece though, as I mentioned in a just completed post.

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post #23 of 30 (permalink) Old 07-08-2015, 10:13 PM
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Quote:
Originally Posted by CHOTIS BILL View Post
In your first set of pictures there is a part that kind of looks like a black dog bone going from the lower link to the top of the knuckle. Any idea what it is. The only thing I can think of is it is there for shipping or maybe some type of anti-sway bar.

Just curious,

Bill Lomenick
Its the vertical link for the upright. Steeda makes a beefy billet replacement because the stock part flexes a lot.

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post #24 of 30 (permalink) Old 07-09-2015, 01:15 PM
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After checking out the cad drawings and other pictures there are several changes made to the IRS which will account for the improvements mentioned. The first major change is the mounting of the spring /shock package. By moving them closer to the wheel and standing them upright will be a major benefit to their motion ratio. You can kind of thinking of it as the difference of trying to wright holding the pencil near the point or holding it near the eraser end. The next thing that caught my eye is the roll center seems to be raised which will make it happier to the front suspension, if the front suspension stayed the same. They also added a rear sway bar which will add adjustability which is always a good starting point. Once I get a car to handle properly I like to adjust the spring/shock package and front sway bar so that I can remove the rear sway bar to maintain as much rear tire compliance as possible. Another change for the better is the upper control arm has an added element to help take braking forces which the earlier one doesn’t have.

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post #25 of 30 (permalink) Old 07-11-2015, 11:51 PM
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OK, I have some additional findings and questions.

Based on my research, it looks like all of the 3.73's are part of the GT Performance Package option that includes the M4204MT ($1,150 List Price on FordParts.com) Torsen Differential as opposed to the M4204M ($199 List Price on FordParts.com) LOK Differential.

From what I see, ALL of the 3.73's have the Torsen and ALL of the other gear ratios have the LOK.
Also, the M4204MT TORSEN is compatible with the 3.31, 3.55 and the 3.73.

Soooo, does anyone know the difference between LOK and TORSEN Differentials?
And is it worth a smooth grand to upgrade if you are really interested in getting power to the ground?
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post #26 of 30 (permalink) Old 07-12-2015, 01:36 AM Thread Starter
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OK, I have some additional findings and questions.

Based on my research, it looks like all of the 3.73's are part of the GT Performance Package option that includes the M4204MT ($1,150 List Price on FordParts.com) Torsen Differential as opposed to the M4204M ($199 List Price on FordParts.com) LOK Differential.

From what I see, ALL of the 3.73's have the Torsen and ALL of the other gear ratios have the LOK.
Also, the M4204MT TORSEN is compatible with the 3.31, 3.55 and the 3.73.

Soooo, does anyone know the difference between LOK and TORSEN Differentials?
And is it worth a smooth grand to upgrade if you are really interested in getting power to the ground?
This thread seems to be getting a lot of traffic on both forums. I responded to this question on the other forum, and will copy the same here. If there are others that can add, please jump in!

I believe your information is correct. Only the 3.73 comes from the factory with the Torsen option. But the assembly can be bolted into one of the other ratios. There is a method to setting up the internals in these diffs, involving shims, checking and setting lash, etc. So unless you know what you're doing, probably should be done by a pro.

The Ford Traction Lok is a clutch style system where the Torsen is a gear style system. No question the Torsen is technically a better system. Do you need to spend the extra money and would you notice the difference? For normal street cruising, probably not. For track use, and apparently especially Auto-X, it is a better setup. I've had regular Traction Lok on my first two builds, and for my purposes and use, it's fine. Not planning to change out the Traction Lok in the new build with the 2015 setup either. I'll spend the money elsewhere. More discussion here FWIW:

https://www.ffcars.com/forums/21-ffr-...-trac-loc.html

https://www.ffcars.com/forums/17-fact...slip-diff.html

https://www.ffcars.com/forums/17-fact...-trac-lok.html

https://www.ffcars.com/forums/66-2006...en-vs-lsd.html

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Last edited by edwardb; 08-09-2015 at 11:42 AM.
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post #27 of 30 (permalink) Old 07-12-2015, 10:43 PM
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Thats correct. Only the 3.73 diffs from the Performance Package cars have the Torsen diff from the factory. All others have Trak Lok.

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331ci, T5Z, .79 5th gear, Wilwoods, and 3 link with 3.73s
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post #28 of 30 (permalink) Old 07-28-2015, 08:10 PM Thread Starter
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Ready to go

Yesterday I finished prepping the 2015 Mustang IRS center section for my upcoming build. I drained the fluid by tipping it sideways and out the axle holes. Probably perfectly good fluid, but I'll feel better giving it a fresh start including friction modifier as specified once it's installed. Plugged the open axle holes with clean shop rags, and cleaned everything up. The iron case just took a little wire brushing with various size wheels in a hand drill and then Scotch-Brite. Peeled the stickers off the rear cover (after taking several pictures) and cleaned it up as well. I sprayed clear Dupli-Color engine enamel on the back cover. Then brushed black POR-15 engine enamel on the iron case after a thorough cleaning with POR-15 degreaser and metal prep. I was careful to not get anything very wet and especially around the front seal. My shop crane was handy for this project. That thing is not light and kind of clumsy to move around. Didn't take any pics yet, but also cleaned up the knuckles and hubs. I'm going to put some clear on the knuckles too, but not until I get the kit and instructions. Best I can tell, as mentioned before, the upper arm gets trimmed back a bit.

This was a relatively lightweight clean-up job given the age and basically zero time on the road. But let's just say I have a new found appreciation for you guys that have the patience to harvest real live donor parts with years of rust and grime to clean up. I've avoided much donor work to date, and probably will keep it that way.

So now I just need a chassis to put this stuff in! We're off to Factory Five next week, with our pickup date of Wed, Aug 5, now confirmed.

Cleaned and ready for finish:

All done. Compare this to the orange rusty look earlier in the thread. Nice improvement.

Clean and shiny rear cover. I'll be interested to see how that vent is handled. I don't remember seeing how it was plumbed when I saw the new suspension at the Open House.

Build 1: Mk3 #5125. Sold 11/08/2014.
Build 2: Mk4 Roadster #7750. Sold 04/10/2017.
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Build 3: Mk4 Roadster 20th Anniversary #8674. 03 of 20. 2015 crate Coyote, 2015 IRS. Legal 04/18/2017.
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Build 4: Gen 3 Type 65 Coupe #59. Gen 3 crate Coyote. Delivered 12/2/2017.
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Last edited by edwardb; 08-09-2015 at 11:44 AM.
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post #29 of 30 (permalink) Old 08-09-2015, 12:12 PM
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edwardb,

Congrats on taking delivery of your 20th Anniversary Kit!

Have you been able to take inventory on the IRS components and figure out what we need in addition to the Kit? I'm wondering about the Differential Vent (I bought FR3Z-4A058-A just in case), Differential Mounting bolts (MPS only shipped me the 2 in the rear cover) and also any bolts or bushings needed for the diff/knuckles.

There seems to be several aftermarket options for the differential bushings to avoid wheel hop like Ford Racing M-4425-M. I'm wondering what FF included (if anything).

Thanks!
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post #30 of 30 (permalink) Old 08-09-2015, 12:59 PM Thread Starter
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Quote:
Originally Posted by RRussellTX View Post
edwardb,

Congrats on taking delivery of your 20th Anniversary Kit!

Have you been able to take inventory on the IRS components and figure out what we need in addition to the Kit? I'm wondering about the Differential Vent (I bought FR3Z-4A058-A just in case), Differential Mounting bolts (MPS only shipped me the 2 in the rear cover) and also any bolts or bushings needed for the diff/knuckles.

There seems to be several aftermarket options for the differential bushings to avoid wheel hop like Ford Racing M-4425-M. I'm wondering what FF included (if anything).

Thanks!
Unfortunately, I don't have too many answers yet. As I mentioned in my build thread first post, it's early for the new IRS. Yes, I've completed the inventory. While I did get a bunch of parts, there are still some backordered including several key components. Plus the instructions aren't available yet. I can tell you the kit does come with poly bushings, steel sleeves, and new bolts for the center section chassis mounts. I'm pretty sure that aftermarket Ford Racing differential mount kit probably wouldn't fit. Since I have the full IRS frame, I can see the Ford stock chassis mounts appear slightly different than the FFR ones. The FFR supplied poly bushings seem pretty hard, so I don't think an upgrade in that area is necessary. At least not yet. The parts list shows new bolts for the knuckle attachments, although I don't have all of them yet. The balance I don't know about. I'm in communication with FF about the backordered parts plus the instructions. I'm hoping to know a lot more soon.

Build 1: Mk3 #5125. Sold 11/08/2014.
Build 2: Mk4 Roadster #7750. Sold 04/10/2017.
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Build 3: Mk4 Roadster 20th Anniversary #8674. 03 of 20. 2015 crate Coyote, 2015 IRS. Legal 04/18/2017.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Build 4: Gen 3 Type 65 Coupe #59. Gen 3 crate Coyote. Delivered 12/2/2017.
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