Ford 8.8 IRS swap

[Cp2295]

Hi everyone just been throwing the idea around of swapping an 8.8 IRS Differential in the back of my mk3. Ive seen kits for sc300s/mk4’s. I have a 4.30 open diff in the Supra now and with the 1j that’s only pushing 310 at the wheels I cannot hookup, tires and wheels are coming first but I gotta think down the line. I have a 3.90 limited slip diff in my garage tore apart but the guy I bought it from didn’t have the shims in it and all the bearings need redone and those things are cheap!! Can only get oem Toyota bearings for these things. And I’ve gotta somehow shim it from scratch without any available shim kits. Just want to know if it’s worth my time and also Im not too certain on the strength of these stock Supra differentials.

So here’s a pro and con list I’ve come up with, just curious if anyone has done it or has input for me.

Pros:
-Loads of gear ratio options
-Very tough differentials
-Parts availability (rebuild kits, etc)
-I have a couple limited slip carriers laying around (I also wheel and have the 8.8 in my wheeler...)
-Huge array of limited slips/lockers (I’d probably opt for a Detroit trutrac gear driven Limited slip)
-lots of ways to beef the axle up if need be (crush sleeve eliminators, 35 spline carriers etc)
-relatively abundant

Cons:
-would have to fab up some sort of a subframe to hold the thing
-axleshafts, don’t really know how I’d go about that part (any insight anyone?)
-driveshaft mounting/length (not too big of a deal)

So what’s everyone’s take?



Sent from my iPhone using Tapatalk

 

[Piratetip]

A few people have done the ford 8.8 rear.

If you are a very adept metal worker/fabricator you could definitely do the swap.
There is no kit for the MKIII to drop it in, its going to be a lot of work.

Ian (IJ) did it way back.
I believe he said he would never do it again, just run with the stock.
But all that is mute as he has moved away from the supra world.
http://www.supramania.com/forums/threads/68588-ford-8-8-diff/page2

Madsupra88 has also done the swap.
http://www.supramania.com/forums/threads/241422-2JZ-MK3-8-8-8-sec-street-car-build

The stock diff is more than capable of putting down power reliably.
There is also a wide array of gear ratios that will fit outside of the stock MKIII ratios:
I have installed:
3.58, 3.73, 3.91, 4.10, 4.30, 4.56
4.88 and 5.30 may also work, but no one has requested those ratios from me yet.

If your LSD carrier is worn out like most I see during rebuild the breakaway torque is likely ~20ft/lbs.
After rebuild with a stage 1 kit I measure breakaway torque @ 95ft/lbs. (Most people use this for the street)
Stage 2 can push that even higher to ~250ft/lbs. (recommend only for track use or serious racing)
Above that you can spool the carrier or install locking plates to allow zero slip.
Solid pinion spacer is the only way to go as well, I don't recommend using a crush sleeve.

A good properly done rebuild will correct all your problems.
The parts list to rebuild one of these correctly is long and is expensive. (Still cheaper than a 8.8 swap)
But the Supra differential is very stout and very strong, it can handle a lot of abuse.

I have only come across 2 supra differentials that were actually damaged beyond rebuild.
From the looks of both they were due to lack of maintenance / loss of oil, can't run a diff with no oil and expect the bearings and R&P to survive.
Otherwise they are all recoverable / rebuild-able, most are just old and tired / worn out.

Another upgrade not many people know about for the Supra differential is moving to a 29 spline pinion over the stock 27 spline.
Allows to run a stronger pinion flange and R&P set, slightly higher cross section of metal / higher load capacity over stock.
This requires a few custom pieces fitted to make work but it bolts right up.

I have a 3.91 diff for sale right now in the classifieds section if you don't want to fool around with a rebuild yourself, fyi.

 

[Cp2295]

A few people have done the ford 8.8 rear.

If you are a very adept metal worker/fabricator you could definitely do the swap.
There is no kit for the MKIII to drop it in, its going to be a lot of work.

Ian (IJ) did it way back.
I believe he said he would never do it again, just run with the stock.
But all that is mute as he has moved away from the supra world.
http://www.supramania.com/forums/threads/68588-ford-8-8-diff/page2

Madsupra88 has also done the swap.
http://www.supramania.com/forums/threads/241422-2JZ-MK3-8-8-8-sec-street-car-build

The stock diff is more than capable of putting down power reliably.
There is also a wide array of gear ratios that will fit outside of the stock MKIII ratios:
I have installed:
3.58, 3.73, 3.91, 4.10, 4.30, 4.56
4.88 and 5.30 may also work, but no one has requested those ratios from me yet.

If your LSD carrier is worn out like most I see during rebuild the breakaway torque is likely ~20ft/lbs.
After rebuild with a stage 1 kit I measure breakaway torque @ 95ft/lbs. (Most people use this for the street)
Stage 2 can push that even higher to ~250ft/lbs. (recommend only for track use or serious racing)
Above that you can spool the carrier or install locking plates to allow zero slip.
Solid pinion spacer is the only way to go as well, I don't recommend using a crush sleeve.

A good properly done rebuild will correct all your problems.
The parts list to rebuild one of these correctly is long and is expensive. (Still cheaper than a 8.8 swap)
But the Supra differential is very stout and very strong, it can handle a lot of abuse.

I have only come across 2 supra differentials that were actually damaged beyond rebuild.
From the looks of both they were due to lack of maintenance / loss of oil, can't run a diff with no oil and expect the bearings and R&P to survive.
Otherwise they are all recoverable / rebuild-able, most are just old and tired / worn out.

Another upgrade not many people know about for the Supra differential is moving to a 29 spline pinion over the stock 27 spline.
Allows to run a stronger pinion flange and R&P set, slightly higher cross section of metal / higher load capacity over stock.
This requires a few custom pieces fitted to make work but it bolts right up.

I have a 3.91 diff for sale right now in the classifieds section if you don't want to fool around with a rebuild yourself, fyi.

Thanks for the input I appreciate it. I’ll get around to rebuilding it someday lol I’ve setup quite a few diffs so not too terrible at it haha. So I guess it seems like a waste then huh? At 95 lb ft breakaway how well does the diff hookup both axleshafts? Also would the diff/clutch packs hold 400-500 hp reliably? If I were to run the 27 spline pinion and a solid pinion spacer or would I have to run the 29 spline pinion..?

Also how do you go about measuring the breakaway, never done that before. Maybe set the diff up in a vice and put both axle shafts in and turn one with my torque wrench and hold the other and see if it goes at ~95 ft lbs..?


Sent from my iPhone using Tapatalk

 

[Piratetip]

The solid collar can be used on either size pinion, no difference there.
I don't have any issues with hookup anymore with the upgrade.
The LSD is engaged well enough to cause a slight chatter on cornering, different people have different levels of this they are comfortable with.
You can control the static friction level on the plates with the LSD additive, add more & they will more easily slide past each other. (PN: XL-3)

I don't see a reason they wouldn't hold that power level.
What kind of application are you using the vehicle in?
If you are expecting to push the diff hard / forcing it to lockup all the time you might consider moving to the stage 2 kit so you don't burn up the plates internally.
You could ask the multitude of people I have rebuilt diff's for to find out how they are performing.
I hear very little feedback from anyone on performance, I try to follow up with them but get little info back.

I welded up 2 holding fixtures that mount to the 2 stub shafts.
No need to hold the pinion.
Clamp 1 stub shaft in the vice and the other you spin, I measure the peak torque with my digital tq wrench.

In stock condition you will measure between 15-30 ft/lbs.

 

[Piratetip]

Another older thread on performance of the Stage 2 LSD kit.
http://www.supramania.com/forums/threads/196305-Weir-stage-2-LSD-upgrade-review!

 

[Cp2295]

I am planning eventually to run mainly track, and do some spirited drag racing occasionally. So for the most part no I do not want to force it to be locked up all the time, just mainly to help launches, but I do need it to corner well still (I don’t mind a little oversteer however actually prefer it). If I want to drift I have that open 4.30 I can weld and keep as a drift diff. I think doing a 95 ft lb breakaway and then playing with the amount of friction modifier would work out pretty good for me, what do you think?



Sent from my iPhone using Tapatalk

 

[Piratetip]

Yeah you could run that type application with the Stage 1 kit.
I would recommend using a minimum amount of friction modifier though the way you are using it.

If you were driving mainly street I would say run a higher level of friction modifier for better drivability / more comfort.
But you are doing the opposite.

You have to give and take, I would live with some chatter on the street for the performance you need on the track.

 

[Cp2295]

Definitely, thanks for the insight really appreciate it


Sent from my iPhone using Tapatalk

 

[black89t]

you're not remotely close to what our stock diffs can take lol. the 8.8 irs setup is for 1000+whp cars that want to launch off a transbrake. there's some decent aftermarket lsd available for our stock diffs. mine has new clutch packs, shimmed, the larger oem spring, and the extra spring. it works pretty dam good. i autox and drag race with occasional track days does it all.

 

[Cp2295]

you're not remotely close to what our stock diffs can take lol. the 8.8 irs setup is for 1000+whp cars that want to launch off a transbrake. there's some decent aftermarket lsd available for our stock diffs. mine has new clutch packs, shimmed, the larger oem spring, and the extra spring. it works pretty dam good. i autox and drag race with occasional track days does it all.

Awesome, good to know-I’m planning on just rebuilding the diff and clutches and throwing a stiffer spring in there. ~100 ft lbs breakaway


Sent from my iPhone using Tapatalk