Hey all, I just ordered a Cusco LSD for my SC and I dorked up and didn't notice the part number was for a car that had a factory torsen LSD in it. My car being a factory open diff car, how screwed am I? I've tried searching around, both here and the internet in general, and I'm getting the impression that it shouldn't matter but I wanted to see if someone on here could confirm or deny that an aftermarket LSD for a factory torsen car will fit into an open diff.

 

None of the SC300's or SC400's ever came with a factory LSD (except for some rare Canadian market SC400's). Soarers sometimes came with factory Torsen LSDs.

The differential type is the Toyota 200mm found in the SC300/400, Z30 Soarer, Supra MKIV NA & TT Automatic (but NOT the 6-speed Supra MKIV TT's), GS300/400, and SC430. As long as the Cusco LSD was for the 200mm type diff from any of these cars then it will install just fine and would even replace a 200mm diff equipped with a Torsen or other aftermarket LSD. I believe our diffs are 10-bolt ring gear type.

The differential that cannot interchange parts with ours is the Supra MKIV TT 6-speed "Big Diff" which is 220mm and 12-bolt ring gear type I think. If you happened to order a Cusco LSD for one of those then no it won't be compatible with our 200mm Toyota diffs.

 

The part is listed for a Mk4 Supra, and I know the NA Supras have the same 200mm diff as an SC, but its a 168 F2 part number which Cusco lists as fitting cars with a factory torsen, but it seems the open diff Supra takes a 167 F2 part number. I've been doing my best to read on the different diffs these cars came with and I think its going to be fine. I've read that only some Canadian SC's had a factory torsen, and various Japanese trims did as well, but no US-spec SC had any LSD. I just haven't been able to read if there were any physical differences, like case or ring and pinion or stub shafts or bearings, between the open diff 200mm and the torsen 200mm.

 

looking at cusco's spec sheet, the 168 F2 is used for their JZS147 aristo and JZS160/161 aristos; both these cars come with 200mm differentials ONLY. This number is also cross referenced to the JZZ30 (only came as a 200mm) and 2jzge versions of the JZA80.

Also I'm not sure what the differences are between the 168 F2 and the 167 F2; as it doesnt strictly seem to be in torsen differentials. AI on google says "the "167 F2" is a 1.5-way LSD, while the "168" is a 2-way LSD"




You are good to run this differential. Just make sure it is installed properly by someone who has done many differentials.

 

I was going off of Cusco USA website. It's not where I ordered from but it has the torsen/open for the 168 and 167. I like your chart better, I wish I had seen it before I asked this question, but thanks for answering it for me anyways.

 

I much prefer using the original japanese versions of the websites; as the USA versions are just resellers/customer support. Heres' the link for the original PDF

https://www.cusco.co.jp/en/pdf/L.S.D._toyota.pdf

 

There are no differences between all the 200mm differentials from the models listed apart from a couple of VERY minor variations in axle stub depth between a couple of TT diffs and NA diffs... but it's an extremely rare difference that only a select few have and even then mostly from MKIVs as I have understood.

OS Giken specifies using 200mm NA axle stubs for at least one of their applications but not all aftermarket LSD makers say this. It is a very rare thing to need to have to do.

You can use the Cusco LSD in any of the 200mm LSD pumpkins with any ring and pinion gear you want from the 200mm SC/Soarer/MKIV/GS/Aristo/SC430 family. And also the 1989-1996/97 LS400 ring and pinion (3.615:1).

 

Hey Kahn, replying here instead of starting a new thread because I'm about to get into some differential stuff that's related to OP's post and have some questions.

So I can keep my stock 92 SC400 pumpkin but replace the ring and pinion and differential from any of those vehicles? I ask cause the differential shop is wanting to source an entire differential because they said they can't find internals separately...I find this hard to believe?

If it's gonna be up on the rack and work done on the diff, what are the best options?

 

Hey-- Yes you can keep your original 1992 SC400 pumpkin AND replace the ring and pinion from any compatible 200mm differential from one of those vehicles.

These specific diffs aren't made any longer but they are plentiful on the used and junkyard markets. But people have also taken many of the open diff versions and welded them and sent them to the moon also. Availability over time inevitably will be reduced... but I think we're still not to that point yet.

The way everyone does it is to have the diff with the ring and pinion you want and the diff with the pumpkin you'll be putting the R&P into (unless you want to keep the donor pumpkin entirely) and combine what parts fro both you want/need to.

The companion flange from your original SC400 diff pumpkin should be kept and reused regardless of which pumpkin you use.

You should be able to buy an all-OEM-Toyota parts rebuild kit from Driftmotion (or Toyota or Lexus... DM just puts it all in one package). The only rebuild parts you cannot buy as a universal fit are the side carrier bushings since this requires measuring what thicknesses are needed at time of rebuilding and then ordering the specific thicknesses required from Toyota or Lexus.

But basically yes, it's better as your shop says to source a donor diff with the ratio you want in order to cannibalize from it to make the custom SC400 diff you desire. Toyota/Lexus likely does not sell the ring and pinion parts separately after all this time.

Do keep your original ring and pinion. You never know when you might need them again or if someone else ma need that ratio.

 

Thanks so much for quick reply and help!

I know nothing about differentials so I wanted to make sure what the parts situation is looking like, what's interchangeable, etc.

Right now the plan is keeping the pumpkin, getting the rebuild kit, keeping the stock gear ratio, and the OS Giken LSD as "well it's already open" splurge...

I'm not 100% sure but I'm thinking my issues are ring and pinion related so it's just one of those things 😞

 

You're welcome!

You'll be able to use the stock SC400 NA axles with the OS Giken LSD (good choice btw!). Only Supra MKIV TT Auto LSD axles sometimes need to be replaced with NA versions for slightly more internal clearance with the axle stub depth.

Get the ratio you want and bring the two diffs, the LSD and rebuild kit to your driveline shop. They can order the necessary OEM side carrier shims in the correct thicknesses themselves after taking measurements.

Make sure your SC400 companion flange is re-used (with a new OEM crush nut) and dial torqued correctly so as to preserve the optimum pinion to ring gear tooth alignment inside after the main rebuild.

Rebuild time is also a perfect time to have the pumpkin casing treated with de-rust spray (POR-15 brand works well) and painted with a POR-15 satin or semi-gloss (a heavy duty dual respirator filtration mask MUST be used due to the fumes being so toxic to breathe directly!). When dry the UV clear protective spray accompanying the POR-15 coat helps preserve it further.