ford4life87

Here's my issue: I purchased a brand new set of 3.73's to go in my 91 5.0 lx vert. Stock gears were 2.73s. So I took it to a guy who says he's done tons of them before and said he would do it for about $300. So a couple of days go by and we get a call from him saying that there was a problem with my rear end, that my car didn't have a posi trak or limited slip in the rear end and that the teeth in the rear end were beginning to look thin and sharp, instead of rounded like they should be. He's now saying I need to pick up a rear end out of a GT coupe or hatch form a junkyard or somewhere and let him put the gears in it and transfer to my car. Do you guys think he knows what he's talking about, or is he trying to pull some stuff on me? The car is immaculate, only 55k original miles, never been driven hard or raced. The only really major thing I've had done to it was I had the tranny switched out from a AOD to 4 speed manual. He says that switch(which the same guy did) was probably what made the teeth in my rear end start wearing like they did. He did say that he would show me the teeth and how wore they were, so I kind of believe him there. But the whole thing about not have a posi trak or limited slip in my rear end blows my mind. I assumed all Mustangs of those years had at least one or the other? Any suggestions?

Tony71502

It should have come with posi. Do you have the title/build sheet, that will tell you the options your came with, including posi.

How do you know the previous owner didn't beat on it? Why would he put in a 4 speed? I don't know for sure but I don't think stock AOD cars had 2.73s, maybe 3.08s.

He's probably telling the truth, but even still I would investigate more about your cars history. 55k original miles... maybe it was rolled over and actually has 155k.

I got lucky with my previous owner, he had a binder full of reciepts and everything that was done to the car down to oil changes.

ford4life87

I know the previous owner didn't beat on it, and that it hasn't been rolled over cause we've owned it ever since dad purchased it on the lot in 91 :-)... I know the car has 2.73s in it cause I checked the code on the inside door jam sticker. Unfortunately, I didn't pay attention to what it said about the posi trak because I just assummed it had it, didn't even cross my mind. The car is at this guy's shop about 50 miles away, so I can't just check the door jam sticker to see what it says about what's in the rear end. As far as the tranny goes, I had the 4 speed put in....cause OMG the auto is awful in those cars. They are notorious for going out, not to mention a stick shift just really brings the old school 5.0s to life!

ford4life87

mjr46

car should have trac-loc factory.

Tony71502

Why not run the 5 speed? If the car came stock with a 5.0, it should have had posi stock. Unless your pops changed out the carrier in the rear, then the mechanic may be blowin smoke up your ***... or maybe the clutch packs are worn out and it isn't operating as a posi anymore. At least he didn't suggest buying a brand new carrier.

nitrous_bob

ugh....

my first clue that it DOES NOT HAVE POSI, is the name of the car

chevy never made a mustang that i can recall.

but yes... all 5.0 cars had an 8.8 trac-loc from the factory which means that as soon as the tire spins... the other locks up for traction. it wasn't even an option to get a 7.5

aod cars could have had all 3 possible gear choices, 2.73, 3.08, 3.27

a change in trans would in no way cause a load on the teeth to wear them in 55k miles

so..... your mechanic is retarded, OR you do not have an original 5.0 car OR your pops put a 7.5" in it with the 40 year old 4 speed, OR your mistaken on what you say

there is no other possibility

mjr46

it could be a SROD 4 speed^^^^^^^ = precursor to the t-5

ford4life87

yes, it is a rebuilt SROD from a late 70s, early 80s GT. :-D

ford4life87

First of all, thank you all for your quick responses and helpful advice.
I think this mechanic is trying to feed me a load of b.s...I'm by no means an automotive genuis but I am intelligent enough to research stuff like this on the net and realize when someone is trying to screw me over. I think I'm going to tell him I don't have the money at this time to do the rear end swap like he's trying to get me to do and take it to someone else for another opinion.