I saw a post from a while back about swapping lsd's and I had a few questions. First, how do I know which one I have? I've got an '88 7M manual targa that I'm slowly working on as the money comes. Second, is if I have the 3.9, how do i find a 4.3? Once I find the 4.3, how much should it cost? And finally, the 4.3 should make it quicker, but what does it do to milage?

Thanks!



PS- please don't smack me...

i don't remember what the pre '89's have. i *believe* it's the 3.73 that you have. you get the 4.3 from a sports package N/A supra. (lucky me, my car already had one, as it was N/A before i did the motor swap.)

cost really depends on the condition of the differential. the 4.3 will definately make a difference in acceleration. i'm turning about 2900 rpm at 60mph. i don't ever calculate gas mileage on my car, as it's running really rich, and i need to tune it.

-shaeff

If you're turning 2900 rpm at 60, then I've surely got the 3.73... I'm pushing over 3500 rpm, maybe more at that speed. So I need to find myself a 4.3...

that doesn't make sense... with a 4.30 differential, you'd be turning HIGHER rpm on the freeway, not lower. you're pushing over 3500rpm in fifth gear on the freeway? that's wicked high, and i'm going to assume that your speedometer is way off!

-shaeff

Well, it's actually busted. One of my speedo cables broke a few weeks ago and I haven't had a chance to take a look at it to see if I can fix it. Anyway, I've been guessing my speed since it broke, and the rpm I gave you was... well, a guess. I had a friend pace it with me the other day and at 60 I was turning about 3000. I guess I've just been speeding by a lot more than I thought recently... good thing I haven't gotten caught...

Anyway, thanks for the help. Again.

i have a 89 rear end on my 90 what kind of gears do i have and by the way it automatic

An easy way to remeber about Diff gears is that the higher the diff ratio the higher rpm you will be turning at a given speed.

All 7MGE Supras have the 4.30:1 diff ratio.

87-88 7MGTE has 3.90:1 ratio, 89-92 has the 3.73 ratio.

This excludes all non US cars.

dammit! i was incorrect. shows how much i know...

Nick > shaeff

-shaeff

FWIW,
My 86.5 NA has a 4.30 LSD in it. I get on average about 25-26 mpg out of it. But, of course, being an old guy (near 50) with kids and mortgage, I NEVER put my foot in it and don't do over 70 (maybe 75) on the freeway. ('Your mileage may vary...')
-Marq

Since the thread was rebirthed, lets use it for info.

LSD is better. Why? How do you know whether or not you have it?

Smaller gear ratios are better. What's the smallest you can get? Are there any aftermarket ones? How hard are they to swap?

First off, while all N/A's came stock with a 4.30:1 differential, most came with an open diff. The LSD was available as a seperate option or as a part of the sport package.

The firewall tag with the car's vin number will identify the diff the car came with... won't help if it's been swapped though:

G284 = 4.30:1 Open
G285 = 4.30:1 LSD
G305 = 3.73:1 LSD
G315 = 3.91:1 LSD

The benefit to a LSD is that if one wheel looses traction the car doesn't dump power through to the one free spinning wheel. For the most part the LSD keeps both wheels moving with equal output. If you want to know more I'd suggest Googling it.

For more information on Toyota differentials and code breakdowns look here: http://toyota.off-road.com/toyota/article/articleDetail.jsp?id=274535


EDIT: It's hard to say that any given end gear is better than the other in a broad scope. It depends entirely on how you drive and what you want. While a 4.30:1 diff will let you put down more power at any given moment it also increases your RPM about 10% at any given speed over a 3.93:1 LSD.

It also reduces your top speed about the same percentage.... granted if you're planning on driving faster than 148MPH frequently then you'd probably already know all this.

This message has been edited. Last edited by: CRE,

Does a "Fill with LSD fluid" sticker on my diff. cover mean I have an LSD?

yes.