I am wondering why a person would swap the stock LSD out of an 87 turbo for the 4:30 LSD? What difference does it make?

if you have the r-154 (turbo) tranny,

first gear= useless
second gear= pretty good
third gear= accelerate like the bat out hell
4th-5th = same as third

all compared to the stock turbo differentials. from third gear on, you'll pull like crazy. a bad side affect is that you'll get worse gas mileage on the highway. by the way, you'd want the 4.3 out of a sport package N/A, that way you still have a limited slip differential.

with an open differential, you'll get NO traction, and do wussy one wheel burnouts...

-shaeff

I have an 87 Supra Turbo - stock differential and stock tranny.

I noticed the 1st, 2nd, 3rd gear thing you speak of already - interesting! So I take it I can do better by finding a N/A sport package differential and swapping it out?

Ok, so now you told me how my setup sucks...

What will it be like with the swap?!!

(now I'm all excited!!!)

It may cost more, but I'd recommend getting a TRD/Torsen LSD upgrade either from one of the online Supra shops or from someone parting out a TwinTurbo-R. I believe this is a 4:10 or 4:11. Not quite as aggressive as the 4:30, but still very nice.

Ok...I think I'm a little lost now on this question...so I have A LOT more (sorry!)...

So...with my 87 stock turbo & tranny...what do I have for a differential?

I understand that there is another (and better) differential I can swap in...a 4.3 out of sport package N/A...correct?

If yes, why is the swap better better? Better top speed? Better accelleration in 2nd (instead of all-3rd?)?

I have seen the TRD LSD but it says it is for the strip and not street driving...I take it I would experience more wear on my tires from swapping it in and that's why there is the "warning"?

Clarification anyone?

The 4.3 lsd will cut off your top speed a bit but you will get a hell of alot more acceleration.

That's cool! But what is the ratio of my stock diff? And why is the TRD diff not recommended for street use?

I am pretty sure the stock turbo rear end is a 3.73. I am assuming the TRD lsd isnt recomended for street use is because it would lock up around turns easily which may be a bother. When i get my new Supra at the end of summer (89 Turbo) i will probably throw the differential off my 87 n/a supra on it.

So if you change from a 3.73 to a 4:30, would my speedometer be off?

But more importantly, and what no one has really explained yet (or at least I didn't catch it), is WHY do it? Does the swap put more load on the engine in the first few gears, thus getting the turbo to spool earlier than 3rd gear? I think THAT would be a great benefit if that is what it does.

Anyway, I looked on car-parts.com for a used differential and it looks to me like the ratios are all 4:30 LSD. So how do I check to know for sure what LSD I REALLY have?

(Is this post a pain in the butt or what?!)

Still lookin' for anwers....

quote:

Originally posted by Brad Helm:
So if you change from a 3.73 to a 4:30, would my speedometer be off?

probably.

quote:

But more importantly, and what no one has really explained yet (or at least I didn't catch it), is WHY do it?

the 4.3 rear makes you accelerate faster. its just how the ratio is.

quote:

Anyway, I looked on car-parts.com for a used differential and it looks to me like the ratios are all 4:30 LSD. So how do I check to know for sure what LSD I REALLY have?

4.3 LSD's came ONLY in the N/A sports package cars. if i remember correctly, the 87-88 turbos had the 3.7, and the 89-92's had the 3.9.

-shaeff

The limited slip was available in any form. Ive had stripped(if there is such a thing) n/a's with the LSD. No TEMS, no sport roof, no wiper washers etc.

87-88 have 3.90:1, 89-92 have the 3.73:1.

The taller gear will spool the turbo faster, but the 4:30 will acclerate harder anyway.

So I assume mine must be a 3.9:1 (since it is a stock 87 turbo). I thought a person could tell from the VIN number or something...

Time to go hunt for a 4.3:1

Where did you guys find this information anyhow? Is there a website where a person can find this level of detail for the MKIII?

Could you even tell the difference between the 3.73 and the 3.90 while driving? or are they so close that it would be hard to feel? Also, if you went from a 3.73 to a 4.30 I'm assuming that it would help your 1/4 mile times? if so how much? (I might be interested in the swap if it's worth it)

Under the hood on the back firewall near the driver, is a placard. It has vehicle info. If the axle code ends in a 3 or 5, it is an LSD. The axle code I think is on the second line, a 4 digit number.

An easy check is to lift both rear wheels and spin one tire. If they spin opposite directions, it is an open diff.