grumpi300

iTrader: (1)

so I have a 1992 lexus sc300 with a r154 out of a mk3 supra. I had the shifter extended to fit from driftmotion.
the engine is currently a factory 2jz n/a with future plans of going na-t. my goal is to be around 550 600hp.
now from my understanding, I want to fit a 3.77 (or 3.769) according to these 2 forums:
http://www.supraforums.com/forum/sho...ferential-Info!
https://www.clublexus.com/forums/per...ough-r154.html
I always wanted to run a mk4 supra subframe with the 3.133 differential, big flange big pumpin big whatever it is. I figured it could handle more power and it would be a little better for highway speeds. but according to the second thread I posted earlier, it would act really weird with the r154. I have seen the mk4 subframe on a sc300 done before. according to the threads, the rear supra subframe is a little sturdier and better overall.
my question is, should I just keep my subframe and install the 3.77, or install a mk4 supra subframe and put a 3.77 in that subframe? also, will the trd lsd differential work on that differential?
from my understanding, the 3.77 differentials come from tt supra automatics. I have tried doing more research but don't know what else to look for.

CatManD3W

iTrader: (18)

the r154 with supra auto tt diff with 3.76 gearing is perfect

Also you dont need to swap out the rear subframe....all you need to do is change the pinion flange on the diff.....i.e remove you old one from SC and swap it over to new diff.....it is as simple as dropping old diff and mounting new one up

Ali SC3

iTrader: (10)

its possible to swap out the rear subframe, but its minimal gains other than cool factor. the rear suspension on a supra is not identical to the SC (its very close) so it may do some small changes here and there but other than the sway bars, big brakes, and diff, all of which you can install in your current subframe, there isn't that much to gain versus the large amount of work it is. that being said several members have done it, and really like it, but most of them installed a v160 at the same time or a similar 6 speed trans, so its a personal preference, but that 3.133 is going to be very long gears without the 6 speed to match it. all the 5 speeds are better suited to the 3.76 unless you just enjoy really long gears or are going for top speed racing.
The 6 speed diff is a little stronger, but the tt auto diff and our stock diff's are not weak at all once fitted with an lsd, in fact they are also very strong, easily strong enough for your goals.

grumpi300

iTrader: (1)

alright. cool. yeah the big brakes fit on our rear subframes anyway from the tt supra. all I know is that the lower control arms change to wishbone and are sturdier. the upper control arms either get shorter or longer, I think shorter for strength. and the sway bar changes completely.
I do feel like the drivability would feel a bit better and its worth it, but only if your done with everything else. I want to do it, but cant justify spending the money for so little gains.
thanks a bunch guys.

grumpi300

iTrader: (1)

last question, if I want to buy a differential, and it says its from a tt supra automatic or from a aristo, how do I know its a 3.76? I think theres a second size too so I don't want to get the wrong one. cause theres one on ebay but it doesn't say the gear ratio? is there any specific way to tell?

CatManD3W

iTrader: (18)

Well first you want to see the inside of the diff to make sure it has LSD......

Also they usually go for around $800-1000...so if it is cheaper its not the one you want....

I have been trying to find a used Supra TT auto diff w/ 3.76 on both CL and Supraforums without any luck btw

Ali SC3

iTrader: (10)

don't mess with the aristo ones from oversees unless you see it has an lsd in it they did not all come with the same options, but a mk4 supra tt automatic from the states comes with 3.76 and lsd, always, unless someones changed it which is why you always take the cover off to verify.

grumpi300

iTrader: (1)

what if i'm gonna be swapping the internals to the trd lsd though? wouldn't that mean that it doesn't matter if it comes with lsd or not, as long as its a 3.76?

Ali SC3

iTrader: (10)

I wouldn't normally try and find the 2 pieces seperately without already having one, but I guess you could try and do that if you want the trd one for sure it makes sense.
I am not sure you can find the 3.76 without the lsd, actually I am not sure what even comes in an aristo to be honest. you can probably do a google search though on aristo's specifically.

grumpi300

iTrader: (1)

i feel like i just over complicated everything ali. lol. i'm sorry.
i just want to know if theres a way to tell if i am buying a 3.76 diff without opening it.
and know that if i buy a 3.76 diff, will the trd diff fit if the differential is equipped with lsd or not.

99SC42

iTrader: (44)

Crawl under the vehicle and locate the drive shaft where it attaches to the front of the rear axle. Place a 6 to 8 inch length of masking tape longitudinally on the drive shaft where it will be easily visible from the side of the vehicle near one of the rear wheels.
Place a piece of masking tape on the edge of one of the rear tires.
Rotate the tire by hand one complete revolution using the piece of masking tape on the tire as a guide.

Count the number of revolutions the drive shaft turns (using the masking tape attached to it as a guide) to one tire revolution. For instance, if the drive shaft rotates three and a quarter turns to one tire rotation, then your rear axle gear ratio is 3.25:1.
if the driveshaft ratates three and three quarter turns then you have a 3.76.9

grumpi300

iTrader: (1)

sweet. that makes perfect sense. I knew how the ratios worked I just didn't think about checking it out that way. haha. thanks 99sc42.

czar07

The TT JZA80 subframe has stronger bracing. The upper control arms are the exact same as the SC (apart from bushings). The lower control arm and the traction arm are shorter. Swaybars are mounted to the subframe mounts and are a different shape.

Best bet for diff is to get one of a Supra Auto TT (3.76 ratio) and get the TRD centre installed.

grumpi300

iTrader: (1)

thanks czar07. a lot of information in one threat for subframes. happy about this.

1A1

FYI, 97-98 Supra TT Automatics had open differentials. Not that it matters if you are going to install the TRD though. You are going the same route that I am going to go although instead of the R154 I am going to use the Supra TT Automatic with the 3.76 Auto TT rear end and the TRD diff.

Steve K