The official LSD gearbox thread

CMS-GT4

Active member
Sticky this one please.

I will post what I learned about 185 and 205 models. Someone else will have to elaborate on the 165.

This link has specs and ratio info on gearboxes.
http://www.celica.dds.nl/en/celihist.htm

All models used a 5speed manual.
4 Gear boxes in all.

All gtfour models had a center VC (viscous coupling) lsd, except for early Japanese 165 models that had a manaul locking center lsd. It had a switch in the cabin.

165 and 185 models came standard with open front and read diffs.
185 models had optional rear torsen lsd but can only be indentified by opening the lsd.

You can learn more about torsen and VC lsd's at this link.
http://www.rallycars.com/Cars/4wd_turbo_cars.html

185 RC/CS/GA and 205 models came standard with rear torsen lsd.

They all have open front lsd and center VC lsd. There is a rumor that the WRC 205 uses a front lsd, but there is not proof as of yet.

There are lsd suppliers for the alltrac.
185/ 205 lsd's are interchangable while the 165 needs modification to use thier lsd. I have heard it needs other rear axels, but I am unsure.

MR2 LSD Conversion for front LSD
We have found that the Mr2 lsd may fit by fabricating a center shaft that has a smaller make end to fit the mr2 lsd. Stock mr2 lsd is VC. This may be a good option for those who rally as VC front and center seems to be a popular choice for rally cars.
Torsen and clutch type lsd's are also available for the MR2 that should fit by the same means as the stock mr2 lsd.
I am going to investigate if parts from the alltrac front diff might be used to modify the mr2 lsd rather then make a new shaft.

GtFout lsd options
Front /Center:
Quaife makes a front torsen type lsd for the gtfour.
http://www.quaifeusa.com/
TRD made a center and front lsd combo for the gtfour that has been discontinued. I have been told by a few rally drivers, one who claims to own one that it is a VC unit. It is a listed as a clutch type, which is a possibillity. Being that they are so hard to find, and expensive at that, they are most likely not an option, and stock center VC will be retained.

Rear:
Cusco and TRD produce rear lsd for the 185 and 205.
Cusco can be obtained through Japan parts.com I have heard good things about them, but never used them myself. Use at own risk.
http://japanparts.com/shop/shop.cgi?mod ... 7s%2fDiffs

Rear torsen from 185 RC or 205 models will be a good upgrade for a standard 185 open rear.

I have read that adding a front lsd can cause understeer, depending on how it is set. From reading the Subaru forums, it seems front and rear clutch lsd cars w/ center VC have a tighter setting for the rear lsd then the front to maintain oversteer.

Supra rear lsd swap:
Another option I read about on http://www.specialstage.com/ is using a rear (lower ratio) supra diff and modify the output of the diff to accept the alltrac axels thus changing the front and rear ratios casing oversteer. If that is a possiblilty then all of the supra lsd options would work for the rear end and give more possibilities. One possible issue is the center diff may over work due to front and rear moving at different speeds and may ruin the center VC. This has yet to be determined.

Gear Sets:
http://www.quaifeusa.com/ Makes a close ratio gear set for the alltrac.
There area couple of other companies that have produced gear sets in the past, I am still looking for their info.

Anyone add what ever useful (factual info) they may have.
 

furpo

New member
very interesting thread.

since my jdm st 185 has a front lsd of some sort and i will rebuild it sometime soon i maybe able to answer one of the questions above as to makes.

with having driven other st185's with two open diffs compared to mine with two lsd's the understair overstair is not a huge issue. even a rear lsd can cause turn in understair. in the end of the day it is a complete package. the suspension geometery, diffs and driver.

roger
 

Kyoto

New member
Does anyone know how difficult it would be to adapt another make of rear LSD to fit the (open) GT-Four's rear setup?
 

furpo

New member
the best idea is to find some clutches out of some other lsd that are about the right size and build a new diff. it is quite straight forward and that way you can get clutches easily.

my mini lsd clutches are from a honda city turbo. the reason i choose them is because of the size and the price.

roger
 

Kyoto

New member
I don't really get what youre saying there. I seem to remember reading somewhere you could use the existing housing and get SW20 or 7MGTE Supra internals and get accordingly suitable output shafts???
 

furpo

New member
if it is only the output shafts that need changing the above option would be the best.

if you have to change the gear ratio and bearing sizes to suit the st185 case then you are better off starting from scratch and building your own lsd like i had to with the front diff of my mini. instead of making your own clutchs as well you are better of finding some OEM clutchs that are about the right size and building a diff around them. the hardest part is getting the ramp angles right.

roger
 

beej

New member
furpo":h6h9had2 said:
very interesting thread.

since my jdm st 185 has a front lsd of some sort

roger

hang on ur saying that the JDM boxes have a front LSD?????

coz i just got a JDM box, and i noticed theres an increase in torque steer under wheelspin, and this would explain it

that means i now have 3 LSD's :| shite
 

CMS-GT4

Active member
I have a JDM RC box, and it does not have a front lsd. However the center diff seems more responsive. If I drive in a straight line, slam on he brakes and floor the gas pedal, I get rear wheel spin for a moment.
 

furpo

New member
beej":32h2wntd said:
furpo":32h2wntd said:
very interesting thread.

since my jdm st 185 has a front lsd of some sort

roger

hang on ur saying that the JDM boxes have a front LSD?????

coz i just got a JDM box, and i noticed theres an increase in torque steer under wheelspin, and this would explain it

that means i now have 3 LSD's :| shite

my car does, the engine and box have been rebuild twice that i know of over its life and i keep on finding all sorts of differences with my car. who knows it may have an st205 box (with aftermarket lsd) or an aftermarket st185 one. i really dont know.

so you may ask how do i know i have a front lsd. first i with the car on a hoist if you spin one wheel all wheels spin in the same driction. even if you hold one of the other wheels it will try spin in the same direction. this was not proof of the pudding so i pulled the front half shafts out and looked through the diff and it is hollow.

roger
 

gtfourdreams

New member
have you guys tried looking at the AE86 rear LSDs? i believe they have a solid rear-end but i remember looking at my old (1993) TRD Japan catalogs and the numbers for AE86 vs ST165/ST185 rear diffs were very similiar. off by the last number, if i remember correct.
 

BraveUlysses

New member
AE86 is definately a solid rear-axle so there is no way a rear end for it would work on our car.

Cold--I doubt that your tranny has a limited slip up front simply because you could floor it and squeak the rear tires. My guess is that your RC box has different gearing (this has been established) and perhaps that gives you shorter gearing at the front wheels and taller gearing at the rear, allowing you to break traction.
 

CMS-GT4

Active member
I know I don't have front lsd. The gearing should be the same on the front and rear diffs on all models. Its the final drive that outputs before the center diff that is the high ratio. 1st and 2nd of this box are lower ratios. I think it was casued by a more reactive center lsd. But its really hard tosay w/o getting the car on a testing course. I'll be gathering much more info once I get my RC clip.
 

gtfourdreams

New member
just wanted to add that TRD has the same part numbers for all 3 gens. the ST165 needs diff side gear shafts apparently. with that in consideration, other LSD's shouldnt be too different.

ST165 86.10-89.8 3S-GTE 41301-ST000
For rear. Side gear shaft required *2
ST185 89.10-94.1 3S-GTE 41301-ST000
For rear
ST205 94.2- 3S-GTE
For rear

*2 41309-20030 QTY 2
Use OE snap ring
(90521-28004*2)


curtesy of http://toyota-trd.jp/en/strt/d_lsd.html
 

mtbgael

New member
CMS-GT4":2qu6smxx said:
I know I don't have front lsd. The gearing should be the same on the front and rear diffs on all models. Its the final drive that outputs before the center diff that is the high ratio. 1st and 2nd of this box are lower ratios. I think it was casued by a more reactive center lsd. But its really hard tosay w/o getting the car on a testing course. I'll be gathering much more info once I get my RC clip.

So there is no "final drive" in our rear differential? It's just simply a differential? This has been a concern of mine as I look into building my alltrac for auto-x in DSP. The class allows aftermarket LSDs, but I always thought if I got a 185 rear it would throw things off by being a different ratio.
 

CMS-GT4

Active member
Another close ratio gear set is offered still bt C-One in japan for about 2,100 usd. Just have to find someone in Japan to import it, as I can not find contact info for c-one. www.c-one.co.jp
Fensport Does carry these though.
They also carry new 205 boxes w/o transfer cases for around 1,200 pounds.

A possible cheaper soultion for a close ratio set is to get a st185 "Rally" box from a limited edition Japan 185. Only the first 4 ratios are close and 5th is standard, making 5th gear of little use for racing. one option is to have a 5th gear made. I myself and looking into having a stadard 185 4th gear modified to be used as a 5th gear for this box. That is if I can locate this gearset from toyota.
 

Kyoto

New member
Though not strictly LSD gearbox related, i heard on another site the strongest GT-Four box made was the "pre facelift model as found on the manually locking centre diff model" because it had to handle the extra stresses of the manual locker??? The synchros are the same as all the other boxes so it still has the inherent weakness there but apparently the teeth on the actual gears are wider. Does anyone know anything about this?

By the way, i have just lined up a 205 rear LSD, yay!
 

BraveUlysses

New member
Kyoto":2ibm2efy said:
AE86 is definately a solid rear-axle so there is no way a rear end for it would work on our car

Hideki reckons he's running an 86 LSD??? :shrug:

Maybe he means a model year 86 LSD rear end. There's NO WAY a solid rear axle would make it on our car.
 

Kyoto

New member
I wouldnt know to tell you the truth mate! When i saw 86 i just assumed that he meant the diff internals from an AE86. They're the same era of Toyota, both 2DR hatchback so i just assumed as much. I think i recall him also running another Corolla 86 component of some sort, perhaps suspension related. RE your theory i don't see how he could be running an MY86 Celica LSD as to the bets of my knowledge they didnt exist. The only (factory) LSDs in the 165s were the centre Torsens and even those weren't fitted to all models. PLease guys prove me wrong because i'fd love to get to the bottom of this. :)
 

CMS-GT4

Active member
Here is a good article on lsd in awd cars.

http://www.wincom.net/trog/autocross/diffs.html

EVO and DMS articles are decent reads since the engine layout and car balance is very simular. More so then otehr awd cars.

I am doing some research on center lsd. I am curious if there is a way to modify the stock center lsd to work faster. The inital lag from viscous can be a problem. Once simple idea was using a phantom grip upgrade to the center with a low tourqe setting to kick in and start the lsd, and then start wearing off once the VC lsd kicked in. There might be a simpler way to just send a center diff and have it modified, but I will post what I figure out.
 
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