well before i asked a question if i had posi cause i layed down 2 tire marks. i didn't try any of your test but somthing alittle funner. i went to a clean cement parking lot. i did 3 burn out. i need breaks and new tires anyways. not long ones but 3 short ones and on 3 of the 3 i left two tire marks. so i am 99% positive i have posi because u guys said i would not be able to lay down 2 tire marks frequently.

 

I'd almost bet money you don't..... because very, very few of those came that way, but it's basically just a bolt-in, so while not likely, it's not impossible either.

The only way to know for sure is to take off the cover and look. All this about "laying down 2 stripes" is BS. Either it does have the parts in it, or it doesn't; all this "testing" is not acurate.

If you haven't changed the fluid in it lately, it need it anyway. Take a look while you're doing the overdue maintenance. And have a bottle of posi additive on hand, just in case somebody has swapped one into your car.

 

A 305 TBI Auto that came with a 2:73 axle. GM normally did not installed a Limited Slip diff on a base car unless it was a special order (305TBI???) I don't think so.

 

I would just get the axel code off the rear end housing, and go look in a haynes manual it will list the gear ratio and will tell if it has a posi unit or not.

 

Don't waste your time on the codes.... if somebody swapped a posi in there, the codes won't show it. I'd bet money that even f you do go to half the trouble of really finding it out, and just get the code, but don't do the last little bit of the work and actually look at it, that it will say you don't have posi. All the codes will tell you is how that particular rear (which may or may not even be the one that came in the car, and may or may not still have in it what came in it) left the factory.

 

Why don't you just jack the car up under the rear axle, put it in neutral and check it out???? if both tires turn same way all time=posi, one spins fwd, one spins rwd or not at all=non-posi

 

That isn't accurate. A torsen posi unit will look like an open diff when you turn one wheel. You need to turn the driveshaft!!! I can't believe this topic comes up every week or so. Same questions, different people. Oh yeah, and if it's a torsen posi it doesn't need additive!!!

 

im not so sure about the "tesing it being BS" part......

if you burnout and EVER only lay down just one strip, short of an act of G0D, you dont have a posi

determining that you DO have one may be impossible, but determining that you DONT is easy

 

Actually that isn't true...this "testing" simply isn't accurate.

I have seen a number of open rear ends that will occasionally lock and give posi-like (or more accurately spool-like) evidence...

However, this wasn't the case...simply the rear ends were getting old and usually when you get posi action consistantly, something may let go. I have seen this twice in the last few years...

RB83L69 is right...Don't be lazy...pull the cover and find out for yourself...

 

im not sure i follow, is your post is somehow telling me that POSIs somtimes leave ONLY ONE BLACK STRIP in a burnout????

 

yup posi cars always burnout leaving only one mark.

jon is right about torsens also. and some LO3s DID get limited slip. (although not a lot)

 

so.....if you leave ONE BLACK MARK, then you DO NOT hvae a posi, LIKE I SAID ABOVE and got told i was wrong

 

Yes...non-posi cars will only leave one mark most of the time...sometimes the rear end will "lock", thus ACTING like a posi...under certain circumstances...

Like I said though...it is usually due to a non-posi rear end starting to fail when it acts like a posi...

Once again...pull the cover and find out for sure...

 

Just a comment that might help... his car is a 89...does that not mean that the zexel torsion posi would not work since he should have 26 spline axles and the zexel posi only works on 28 spline. Unless his axles were switched of course.. i doubt anyone would spend 320 bucks on a posi for 3.08 gears or lower assuming he does have 2.73s

 

The changeover was in 89...so it could be either...

We can guess all day long...but actually inspecting it will be the true answer

 

just take 10 minutes and pull the cover

 

Stop doing BURNOUTS and he would not have any concerns if it is a Limited Slip or not.

 

The jack up and spin test does work, but pulling that rear cover is kinda a no brainer in that if it is in there it won't be hidding


And 305 TBI's did get POSI, my 92 RS had it!!

 

stop breathing
he can do burnouts if he wants to, and ya cant stop him.

Drakar like Jon and I have said the jack up and spin test does not work with Torsen posi - like the $99 unit from SLP.


and i was joking when i said posi cars only spin one tire when the burnout. c'mon.


another vote for pull the cover and change the lube/oil/whatever you want to call it........

 

Just take a 13mm, and 5 minutes of your time to pull the cover off. Also, a posi rear can frequently leave only 1 mark. If the posi is worn or going bad, it can actually happen quite often.

 

my car has done that a few times. once i was just doin a brake stand and only left one mark and the other few times ive left to strips of rubber and i found out one owner put a posi in it like id have to say about 10yrs ago, so it could be worn out. i gotta pull the cover and check. i think thats the real true way to findin out instead of those "tests"