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

[Racingboy532]

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...

 

[LX302]

Ok, I have some answers but not all.
If the claim is right about the 90-91 GT Mustang, and not out of any other Ford vehicle, it could be one of 2 things.
All stock cars in 90-91 came with either a 2.73. 3.08 3.27 or 3.55. But it could be also be 3.73 if it was dealer installed or done at a later date by the owner. But my bet it's a 2.73.
I can't verify the numbers you posted off the casing or tag. Maybe someone else can help. But the numbers you listed, are they off the tag you found on the diff?

If you want to upgrade it to 3.73's, you can use the same trac-loc, but I would rebuild the clutch pack with new axle bearings and seals.

You have some open, try this....you can check the axle ratio counting the teeth on the ring gear. If they are Ford gears, you will probably also find the ratio stamped on the ring gear.
Ring Gear Teeth 30 37 36 39 41 41 41
Pinion Gear Teeth 11 12 11 11 11 10 09
Axle Ratio 2.73 3.08 3.27 3.55 3.73 4.10 4.56

 

[Racingboy532]

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.

 

[bill302]

S = Sterling differential is the manufacturer,215 = Model number,a = Revision identifier. S215a. the x(missing number) is supposed to be a 2 and the the 2L73 stands for factory installed 2.73 gears with a Traction- Lok the L IN 2L73 stands for traction lok.the 88 is 8.8 which is the ring gear size. and 0m17 1s the exact date axle was built in code 0=1990 m=12th month and 17=17th day.this code represents what the axle left the factory with and dates but as you know the gear size and locker may be different because of upgrades...

 

[bubba-dough]

.

 

[Racingboy532]

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

Thanks for the help!

 

[skip nay]

Ok he probably or someone else changed gears if he is telling you it has 3.73's. You can check this by turning the axle one full turn and watching where the driveshaft gets bolted onto and seeing how many times it goes around. 3 and a half times would be 3.55's and 2.73's would be 2 and three quarter turns and 3.73's would be about 3 and three quarter turns.

 

[bill302]

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

Thanks for the help!

on the diff. tag the 215 is the model number the 2L73 is the gear size installed at the factorywhich is 2.73 gears and the L stands for traction-lok.so your axle came equiped from the factory with 2.73 gears with a traction lok.but these gears and traction lok could have been changed the easiest way to see which gears are installed is to remove the differential cover and turn the ring gear until you see the size of the gears installed the size will be stamped on the side of the ring gear. and sometimes the gear size will be stamped on the pinion headin both cases you will have to spin ring gear to see.


can one use the exisiting 2.73 trac-lok carrier (I know, rebuild it) with a new ring and pinion?
yes!

 

[Racingboy532]

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.