daJZguy

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?

88supramki

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?

99SC42

iTrader: (44)

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

SC51

iTrader: (3)

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.

88supramki

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

account2x

iTrader: (5)

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

SC51

iTrader: (3)

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.

daJZguy

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

daJZguy

what year gs400 does it matter

daJZguy

i think its too short

daJZguy

the difff from your car is it the 400?

99SC42

iTrader: (44)

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.

TLDriver

iTrader: (4)

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.

88supramki

^^
You've got a PM TL

account2x

iTrader: (5)

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.