LSD swap for the SC400 ???

[1UZinator Fabricator]

I am trying to improve the gas mileage on my SC400 while also improving traction with a Torsen diff. I have read that the JZA70 8" Torsen spool will fit in the SC diff. I have also heard that the SC430 and SC400 diffs are interchangeable. I have ordered a SC430 diff for the ring & pinion (may just use entire diff with Torsen spool replacement). So now my question -> Is the JZA70 spool interchageable? I have also read conflicting info on the internet that says it is not interchageable at all.

I want to go with Torsen and a higher ring/pinion ratio -but I do not want to spend several thousands by just buying an entire Torsen Diff. Will any of the Torsen spools that are often found on ebay -fit with no modifications (other than shimming the lash)??

Help please! Many thanks!

MP

 

[AutoLuxLexES]

Heres a list that will work to help with mpg
Sc400(98-00)
Ls400
Sc430
Gs400
Supra auto tt

As far as torsen, i only know that stock soarer and mkiv supra tt auto work
What is a jza70?
Charley

 

[4U2QUIK]

jza70 is the mkiii supra that came with the 1jzgtte.

 

[1UZinator Fabricator]

I just found an old thread in the Club Lexus forums about this. It is a complete "drop-in" for the SC400 diff case. So I purchased the Torsen spool and it should be on the way shortly. Many thanks for those that tried to help.

 

[xspsi6]

The jza70 diff will not really work without major fab work due to the axle tulip issues

 

[1UZinator Fabricator]

The jza70 diff will not really work without major fab work due to the axle tulip issues

It has been done several times without any modifications. "It is a simple drop-in". Keep in mind that I am referring to the JZA70 auto trans LSD "Spool only" (200mm ring) which is different from the TT 6-speed (220mm ring). This is also not a TRD piece -which does require shortening the stub flanges (tulip?) at the splined ends a bit (according to what I have been reading). But on the Club Lexus tutorial (with pictures) the JZA70 spool goes into the SC differential with no modifications. I thought the article that I read was on Club Lexus -but here it is:

http://www.clubna-t.com/forums/showthread.php?p=10103

Enjoy!

MP

 

[xspsi6]

Jza70 is a mk3 supra and a jza80 is a mkiv supra so did you mean jza80?

 

[1UZinator Fabricator]

Jza70 is a mk3 supra and a jza80 is a mkiv supra so did you mean jza80?

No. THe JZA80 is a 220mm ring gear spool with 12 bolts while the JZA70 is a 200mm ring gear spool with 10 bolts.

The SC300 and SC400 are both 200mm spool 10 bolt diffs and so the JZA80 will not work. The entire pumpkin with JZA80 can be swapped from the MKIV TT 6-speed if you change the yoke on it to match the one from the SC300/400. THe cases are slighly larger to accomidate the larger ring gear. But from what I have read -the mounting points are the same.

But the huge difference is that a JZA80 diff is running around $1500 USD or more while the JZA70 spool is a little over $500 delivered from Japan. If you want -as soon as I get mine and swap it in -I can take photos. But the threads with photos have already been done as with the previous link and so it would be somewhat pointless for me to re-create a how-to thread since there are already several out there.

I already have a 3.92 set of gears which I will be swapping for the 4.27 gears for track days and a set of 3.26 on the way for highway cruising and slightly better fuel economy. I will set the two pumpkins up seperately so that all I have to do to make a trip to the track is to swap out pumpkins and tires.

 

[AutoLuxLexES]

Not all jza80 have 220mm ring gear, only tt 6speed, rest of jza80 are all 200mm
Charley

 

[1UZinator Fabricator]

Not all jza80 have 220mm ring gear, only tt 6speed, rest of jza80 are all 200mm
Charley

From my readings of articles JZA70, JZA80 and JZA90 are chassisl codes with associated diffs. From my readings -the JZA70 and JZA90 are 200mm with 10 bolt, and the JZA80 is the 220mm 12 bolt. I haven't read anywhere about a 200mm JZA80 housing.

References:
http://www.trdparts.jp/english/parts_lsd_mechanical.html

http://www.mkiv.com/techarticles/auto_to_6spd_swap/differential/index.html

http://v8soarer.com/diffs/index.shtml#Other

http://www.supraforums.com/forum/showthread.php?593258-rear-end-gearing

Just found an article that seems to lead to 200mm JZA80 diffs:
http://www.turbosupras.com/pages/pages/technical/jza80/Differential specifications.htm

Regardless of size of JZA80 -I bought the JZA70 diff because I know it is the 200mm ring size (same as SC300/400) and that is the one I need.

MP

 

[xspsi6]

Jza80 6 speed is the larger 12 bold and the rest of the jza80 cars are 10 bolt so n/a tt auto cars have the lsd you are looking for which is a common swap also jzz30 soarer cars can have them as well.

 

[RobSCV8]

TT 6 Speed, or "Big Diff" isn't an option unless you don't mind fabricationg bits to make it fit.

Any of the the other MKiv supra/ soarer diffs will fit. I just fitted an LSD to the V8 from a 5 speed N/A Supra has the same final drive as the manual Soarer.

I also the diff from an SC430 will fit.

There is a list of compatable, read simply swap, diffs out there I'll see if I can find it.

 

[1UZinator Fabricator]

I also the diff from an SC430 will fit...

That is correct from my readings. So I already have one coming today that I picked up really cheap for the 3.26 (gas economic) gears. I think I have decided to leave the 3.26 pumpkin as open diff and set up my SC300 pumpkin (4.27 gears) with the Torsen unit. Then I can cruise on the highway with decent economy and swap the pumpkin for weekend racing on occasion. Now I just need to drop about 800 lbs of weight without making the car look, feel and drive like a Honda Civic!

 

[brawls43]

Reading the link you sent from clubna-t its talking about the Supra TT auto trans, from the MkIV being the drop in diff for SC's. I haven't read the other references yet, but I'm curious to hear if the MKIII JZA70 torsen fits. Those are much easier to find for a decent price.

 

[1UZinator Fabricator]

Reading the link you sent from clubna-t its talking about the Supra TT auto trans, from the MkIV being the drop in diff for SC's. I haven't read the other references yet, but I'm curious to hear if the MKIII JZA70 torsen fits. Those are much easier to find for a decent price.

It should fit seamlessly from everything I have read. I have found several threads where people have said they have already been running this torsen in the SC cars. And yes -it is much easier and a bit cheaper to get your hands on. $500 USD for the 200mm unit vs $1500 for the 220mm one is much more appealing. And I don't plan on putting down enough power yet to break the 200mm one. If I start pushing those boundaries -I will reduce the weight first before spending a share of Ft Knox to convert to the larger one. If it had to come down to it -I could always loose 40 lbs from my gut too which would be better for my health and easier on my wallet.

I should be getting the Torsen spool here (coming from Japan) sometime next week and I will then post up the results.

 

[Spinnetti]

Reading the link you sent from clubna-t its talking about the Supra TT auto trans, from the MkIV being the drop in diff for SC's. I haven't read the other references yet, but I'm curious to hear if the MKIII JZA70 torsen fits. Those are much easier to find for a decent price.

Greg, I don't have all the facts, but when I researched the old supra LSD's it wasn't a match for the LS - not in the case, or in the internals. if you want more gear, the R&P from the 6cyl A/T sc is a 4.27 and is what I'm running.. In fact, using the whole SC diff, and modded my subframe to mount it.

 

[brawls43]

Greg, I don't have all the facts, but when I researched the old supra LSD's it wasn't a match for the LS - not in the case, or in the internals. if you want more gear, the R&P from the 6cyl A/T sc is a 4.27 and is what I'm running.. In fact, using the whole SC diff, and modded my subframe to mount it.

Spinnetti, we're running the 4.27. It was nice help on 1st and 2nd gear accelleration, but it crushed our fuel economy at Road America. Way worse then we thought it would. I'm still trying to sort out our rear spring rates, we get unload the inside tire on too many turns, particularly hard right handers. Which then makes it hard to get the power down. Been trying to find an NA mkIV supra LSD, to no avail.

 

[Spinnetti]

Spinnetti, we're running the 4.27. It was nice help on 1st and 2nd gear accelleration, but it crushed our fuel economy at Road America. Way worse then we thought it would. I'm still trying to sort out our rear spring rates, we get unload the inside tire on too many turns, particularly hard right handers. Which then makes it hard to get the power down. Been trying to find an NA mkIV supra LSD, to no avail.

Yeah, RA needs the 3.6 gear prolly. My fuel consumption is bad... 9-10 gph or so. I searched a long time for an LSD and just got really lucky. Get a spare diff and weld up the spiders? I ran a welded rear before. Worked on track, but a pita in the pits. I'm running 800lb front and rear $30 eBay Honda kit for all 4! But rear rate is too high. 400lb is probably enough. May change at some point, but a little oversteer never hurt anybody I got new wheels 9" with wider tires - going from 225 to 255, (245 in front on8") and I'm hoping that will balance it out. If not, l'll soften the rear springs. The real value for these cars is going to be the 5 speed, but I havent cracked that yet, but will try to do at lemons prices before next season.

 

[brawls43]

I've been thinking about switching our spring set up to the coil-over style. I'm eyeballing some used Bilstein's, which would work perfect for it. The 5 speed would be ideal, but I'm a bit nervous about the controller situation. I'd love to swap in the newer engine and everything, but there's no way that would pass budget. I found a local 5 speed auto that I'm thinking about picking up, but I haven't pulled the trigger yet. I'm more tempted to just do a 5 speed manual. Its more expensive, but the swap is just fabrication and buying parts. No voodoo black magic programming mumbo jumbo.

And sorry for the threadjacking...

 

[Spinnetti]

I've been thinking about switching our spring set up to the coil-over style. I'm eyeballing some used Bilstein's, which would work perfect for it. The 5 speed would be ideal, but I'm a bit nervous about the controller situation. I'd love to swap in the newer engine and everything, but there's no way that would pass budget. I found a local 5 speed auto that I'm thinking about picking up, but I haven't pulled the trigger yet. I'm more tempted to just do a 5 speed manual. Its more expensive, but the swap is just fabrication and buying parts. No voodoo black magic programming mumbo jumbo.

And sorry for the threadjacking...

Can't see how to do a manual within legal budget... It might be possible, but I don't know how, hence my sticking with the automatic. I'll be able to get that going sooner or later within $ limits...

If you don't want to weld up the rear, soften your rear springs a LOT. Most people run simply too much spring (I am too, but I didn't know the rate before I bought them).. in my "Real" race car, I'm only running 175# rears (live axle, RWD)... Used Eibachs are cheap and come in practically any rate.