so I converted frrom auto to manual in my sc4001j, i notice gear ratio is not what it supp to be, whats a diff thats inexpensive that will work apart from the twin turbo supra?

 

What year is your SC4? You might be able to stumble on an Aristo rear diff at a reasonable price but don't expect to find it quick.

Is the gear ratio too tall? Or too short?

 

the stock sc4 rear end should be fine it's a 3.92 i had that on my R154 and it was fine.
The ratio is too short i think, well you can get the diff out of a gs400 which is 3.26 that works great also.
gl

 

Ya I'm with Omar on this one. The 3.9 should be great for it. If you go with the 3.2 rear like I'm running you neeed boost or your gonna be a slug.

 

I'm gonna source a 3.9 for my car prior to my swap. should be a lot better than my current 4.27 :/

 

3.2 will be a slug with boost. That is the 6spd gearing.

 

Lol not mine. Its more like a Jet that just keeps pulling

3.9 gave it a bit more torque (street fun), but I can sacrifice that for top end any day.

 

first of all , i appreciate all the responses in this day and age i thought everyone was to themselves but neways the car is a 92 sc400, with a 1jz thats was making 440hp automatic on 15 pounds so it has boost, but converted to r154 5 speed and thr lower gears are short it revs so quick but doent go in boost at almost 6000 rpm so i really get nothing out of 1st and 2nd

 

what year gs400 does it matter

 

i think its too short

 

the difff from your car is it the 400?

 

all the gS400 and 430/ SC400 from 98-2000 and 01+sc4300 and LS4300 all have the smae gear ratio 3.26 that diff will be perfect for your setup.
try it.

 

I have one sitting at the shop... Not sure what's wrong with it but I just pulled it out and put in a new to me diff.

 

^^
You've got a PM TL

 

bit is an understatement

http://www.physicsforums.com/showpos...42&postcount=2

Gearing is all about torque manipulation. The JDM is rated 320 ft/lb of torque so I'll use that for this demonstration.

320 x 3.266 = 1,045

v160
3,999
2,466
1,761
1,371
1,045
829

r154
3,397
2,042
1,369
1,045
787

With 3.266 differential you'll lose 600 ft/lb of torque in 1st gear and 424 in 2nd gear.
Top speed is 155 mph @ 6800 rpm in 4th gear.

320 x 3.769 = 1,206

3,920
2,358
1,580
1,206
908

With the 3.769 differential you'll lose only 79 ft/lb in 1st gear and 108 ft/lb in 2nd gear compared to the v160.
Another way of looking is you'll gain 521 ft/lb in 1st gear and 319 ft/lb in 2nd gear compared to the 3.266.
Top speed is 134 mph @ 6800 rpm in 4th gear.

320 x 3.916 = 1,253

4,073
2,449
1,641
1,253
943

With the 3.916 differential you'll gain 74 ft/lb in 1st and and lose only 17 ft/lb in 2nd gear.
Or gain 674 ft/lb in 1st and 407 ft/lb in 2nd compared to the 3.266.
Top speed is 129 mph @ 6800 rpm in 4th gear.


Are you trapping higher 129 or 134 mph? If not the higher speed is compromising your acceleration. If so you're best off going with a v160 and 3.266 differential swap because of the inherent torque loss.