IS300 M85/M98 rear diff - does it fit?

[mrk1]

Originally Posted by fika84

That's a nice surprise! My understanding is that none of the lexus rear ends are clutch type. Where did you read/see that they were?

You're boosted though right? So are you just going to bolt up this rear and for the longer gears?

Yes I wanted a longer gear as I am turning up the boost and turbo size, longer gears mean more time in boost. I was just searching around some where it mentioned a clutch type but you never know if you can trust what people write. Exactly why I opened this diff to confirm.

[fika84]

Originally Posted by mrk1

Yes I wanted a longer gear as I am turning up the boost and turbo size, longer gears mean more time in boost. I was just searching around some where it mentioned a clutch type but you never know if you can trust what people write. Exactly why I opened this diff to confirm.

Nice! I also bought a used IS300 carrier, but just for the carrier to put a new diff and fd into so my car wasn't out of commission I'm selling the 3.909 that I took out of it. Good times! I love reading your build thread btw, you make some awesome stuff!

[mrk1]

Originally Posted by fika84

Nice! I also bought a used IS300 carrier, but just for the carrier to put a new diff and fd into so my car wasn't out of commission I'm selling the 3.909 that I took out of it. Good times! I love reading your build thread btw, you make some awesome stuff!

Thanks, I saw your for sale thread right after ordering this diff. I would have bought those from you other wise haha. Looks like my impulsive habits actually paid off this time.

[slicktop]

I have an M85 in my car. It was a direct swap from the Y38.

[B T]

is the IS250 the same carrier?

[Jeff Lange]

Originally Posted by B T

is the IS250 the same carrier?

Yes, but different internals (no LSD).

Jeff

[TRACE_on]

I am building my motor and running E85 this year on my turbo FRS so I would like to do this differential swap. However, I am having a heck of a time finding a M85 3.73 differential.

Is it possible to just swap the ring and pinion from Lexus into the stock FRS differential? The ring and pinion can be puchased brand new if needs be: https://www.lexuspartsnow.com/parts/...201-80781.html

[mrk1]

Originally Posted by TRACE_on

I am building my motor and running E85 this year on my turbo FRS so I would like to do this differential swap. However, I am having a heck of a time finding a M85 3.73 differential.

Is it possible to just swap the ring and pinion from Lexus into the stock FRS differential? The ring and pinion can be puchased brand new if needs be: https://www.lexuspartsnow.com/parts/...201-80781.html

Sure you can buy new, 3.73 ring and pinion also came in MK3 Supra.

[TRACE_on]

Originally Posted by mrk1

Sure you can buy new, 3.73 ring and pinion also came in MK3 Supra.

Sweet, are there any other pieces that are needed for a swap other than the ring and pinion? I am assuming that most people are doing this for the 3.73 instead of the stock 4.10, not because the M85 diff is stronger than the stock FRS diff.

[200hp/tonne]

You can also look at aftermarket ring and pinion gears that were made for toyota trucks but fit the IS250/300/FRS/BRZ carrier and diff without problems. I built a pumpkin with new gears and OS Giken diff using a IS250 casing with gears from https://www.nitro-gear.com/category-s/594.htm
There are plenty of parts required with a ring and pinion swap, namely:
- new crush spacer between pinion bearings
- new set of shims for pinion depth
- new shims for differential side bearings
- new pinion shaft seal (very difficult to remove pinion without damaging this seal)
- if using the Nitro ring and pinion, then a new pinion yoke (nitro pinions have a different spline on yoke attachment)
- no matter where gears are from, getting the pinion bearings on and off to set pinion depth and preload is a pain in the a$$ and inevitably destroys one or more. So i would say 2 sets of bearings

not expensive, just a lot of things to keep in mind, maybe it would be easier to buy a low mileage M85

[TRACE_on]

Originally Posted by 200hp/tonne

You can also look at aftermarket ring and pinion gears that were made for toyota trucks but fit the IS250/300/FRS/BRZ carrier and diff without problems. I built a pumpkin with new gears and OS Giken diff using a IS250 casing with gears from https://www.nitro-gear.com/category-s/594.htm
There are plenty of parts required with a ring and pinion swap, namely:
- new crush spacer between pinion bearings
- new set of shims for pinion depth
- new shims for differential side bearings
- new pinion shaft seal (very difficult to remove pinion without damaging this seal)
- if using the Nitro ring and pinion, then a new pinion yoke (nitro pinions have a different spline on yoke attachment)
- no matter where gears are from, getting the pinion bearings on and off to set pinion depth and preload is a pain in the a$$ and inevitably destroys one or more. So i would say 2 sets of bearings

not expensive, just a lot of things to keep in mind, maybe it would be easier to buy a low mileage M85

Thank you for all the info. I think you are right, it would be a lot easier to find a good-condition M85 diff. If that doesn't play out I will look at the other options.

[mrk1]

Originally Posted by TRACE_on

I am assuming that most people are doing this for the 3.73 instead of the stock 4.10, not because the M85 diff is stronger than the stock FRS diff.

Right