Rear axle q's - yes I've searched...

I am looking at an 8.8 a guy has for sale. He claims it is an 8.8 3.73 ratio'd trac-lok out of a 90 or 91 GT. The rear is by itself, no car attached. The door jamb tag is in a junkyard somewhere...
I looked at it, recognized it as an 8.8. I took all the numbers I could find off the diff tag...they are:

s215a
xL73 88 om17

Now...yes, I know now I am missing a KEY number (where the x is)...I did not know until last night some of the numbers can hide under the diff bolt covers...Oi!

I realize this is most likely a 2.73 trac-lok....but on with the post!

Anyway, I thought I had enough information to figure it out from the Chilton manual...but alas...no such luck!

In the Chilton manual, all the code refernce numbers work from the door jamb tag...I know I can rotate the rear and count revolutions (or take the cover off and count some teeth). I will do this anyway to verify both gear and trac lok function (I know, no gaurantees on the trac lok)...

The questions:
In the Chilton manual, they list several ratios for Mustang rears, from 2.73 all the way to 3.73 in conventional and limited slip. I don't remmeber them all but there is: 2.73, 3.08, 3.27, 3.45, 3.55 and 3.73. The manual doesn't appear to differentiate between the 7.5 and the 8.8.

Anyone know why?
What ratios did the 8.8 come in?
The 7.5?
Is there anyway to use the plant codes to determine the rear (crazy, I know but I have to ask)?
One more: can one use the exisiting 2.73 trac-lok carrier (I know, rebuild it) with a new ring and pinion?


I have an open 7.5 (5 speed) under the 4cyl car with a 3.45. I have parts car with an open 3.73 (auto). I have an 8.8 under the 5.0 with a 2.73 trac lok. There is also a 7.5 3.73 trac-lok ring gear and pinion on the shelf from some 7.5 rearend....and none of this is helping me out!

Thanks and sorry for the rambling post...

Thanks for the reply.

I am pretty sure it is a 2.73, just hopeful is all. The numbers I listed are from the diff tag bolted to the diff cover. I am aware the tag is the factory and nearly anything could have happened since the rear was orginally built.

Thanks for the info on the trac-loc. If I go this route, I'll rebuild with new bearings, seals and trac-loc rebuild.

The gearset on the shelf is a 3.73 and is stamped as you say. 41 on the ring, 11 on the pinion.

Another option I have is an axle from a Turbo Coupe, which may suit me better...although it is twice the price as well.

Okay then, does the model number "215" actually identify this as a 2.73 trac loc rearend?

Thanks for the help!

I really don't think the seller knows if it is a 2.73 or 3.73. They saw the "73" and assumed. They probably don't even know there is a 2.73 and a 3.73.

Regardless, my point of the post was to determine what ratios exactly the 8.8 and 7.5 had. The Chilton's manual I have is not specific about which ratios go with what rearend. It just lists the range, which is why I am speculating about this one. I realize there is a 95% chance it is a 2.73, assuming the case has never been opened. I know the only way to verify is by opening and/or counting the revolutions.

I was only hoping to salvage the info I collected without making a trip back. I haven't been able to raise the guy on the phone since I visited.