Joonas

thinking about buying an 88 rx7. would it come with a posi rearend or whats the best type to put in it for posi?

Rxmfn7

iTrader: (4)

"Posi" , or Positraction is Chevy's term for their Limited Slip Differentials (LSD). In an rx-7 it would depend on what model it is to as if it has a LSD or not. What model is the one you are looking at? (GXL, SE, Turbo2.....)

SureShot

The turbo & GXL models generally had LSD's, but you need to jack a rear wheel with the tanny in neutral & turn the tire to feel for the LSD friction.

GLHS

I have found that all 88s have LSD, unless broken. reguardless of model.. I have a SE and it has LSD..

Joonas

the one im looking at is a 1988 Rx7 TII 125 original km everything seems to be in good shape except there is a dent in the front drivers side fender but I figure for $2000 cdn its still a pretty good deal. But the guy who owns it wont let me take it for a drive by myself he always goes with me so I cant see how she does under a bit of abuse though

Rxmfn7

iTrader: (4)

All Turbo2s had LSD. That sounds like a great price too...

Joonas

LSD? Limited slip, Dosent that mean that whatever wheel that will spin the easest will spin I want both to spin at the same time, Positraction, or am I just confused

Rxmfn7

iTrader: (4)

No, when the wheel that spins the easiest gets all the power that is called an open differential.

scathcart

You're thinking of an Open differential.

Positraction is a GM brand name for a limited slip differential. Ford's brand name was "Trac-loc".

An LSD IS Posi. The slippage between both tires rotating is limited with an Limited slip differential. (ugg, that is way too dumbed down...)

Rxmfn7

iTrader: (4)

That's my new favorite quote of all time

scathcart

I thought that one would be enjoyed... but how else do you put it in layman's terms?

In actuality, the 86-88 LSD is a clutch-type system, where the rear axles are ordinarily locked together via several clutch disks and locking plates sandwiched together, pressed together with a pair of springs. When the tires have to rotate at different speeds (such as when turning), the clutch paks break their girp loose and slip against the metal locking plates.

This slippage is what requires the LSD additive in clutch-type differentials to make the lfuid more slippery... otherwise the clutch plates shudder.

Ford Trac-loc is almost identical.

The 86-88 LSD's wear out very quickly (as short as 50K miles), but are rebuildable.

Rxmfn7

iTrader: (4)

Yep, but the 86-88 type LSD is better when working properly correct?? And also, I always hear of people saying that check for LSD by jacking the rear up, and rotating the tires. If the wheels spin in the same direction, or opposite direction.....it means something. I dunno really. Could you elaborate on this a little?

scathcart

86-88 is better, but the 89-91 viscous one does not wear out.

The best way to check for LSD is to light up the tires, with one tire on pavement and one tire on grass. With an Open diff, only the tire on grass will spin. With LSD, you'll get tiresmoke from the pavement.
(open diff routes power to the tire that will spin the easiest)

You can also jack up the car... open diff will spin both tires, but they will oppose each other. LSD should make both tires spin together in the same direction. Put the car in neutral and turn the driveshaft for this test.

Rxmfn7

iTrader: (4)

Hmm... thats strange because on my GXL if I spin on wheel by hand, the other side will turn the opposite direction. But like you said It will spin both tires even on eneven surfaces.....

Joonas

so if the LSD is woren out will it be the same as a open diff or would I still be able to light em with both wheels? cuz not only does it look stupid doing burnouts with one wheel but your tires will where diffrent and you couldent have that cuz there always seems to be one wheel that prefers to spin

cbrinega

So what does it mean if you have both rear wheels jacked up, rotate one, and the other doesn't move at all? Is my LSD broken? (1990 GXL)

rx-7fc

how do you tell if your lsd is worn out i have a 86gxl and when i try to do donuts it will only do one wheel but when you start out it will do two but when it comes around it only does one and i have to stop because it goes to big or i will hit something and the wheels that spins real fast it the left one

Icemark

OHHH stop your making my brain hurt... I can't think at the speed of a 286 computer.



Perhaps you should have told him that a Posi is a LSD...

Calling all LSD's a Positraction is sort like calling all sports cars a Corvette, just because GM does it, doesn't make it right.