How do you tell what type rear I have

[bil1024]

Its a 5 lug rear from a mustang, but no tag on the pumpkin. Guy told me it had 4.11 gears, which if it does, I have to change. How do I tell after opening up the differential ?

[MTSCustoms]

Count the splines on the ring gear, and the splines on the pinion. (Put a mark on one spline and count til you get the mark again). Divide the larger number by the smaller number and you have your gear ratio.

[michael everson]

I think the gears are labeled. If not turn the axle one revolution and coount how many revs the pinion makes
Mike

[Jeff Kleiner]

The guys told you how to determine ratio but some other things to keep in mind---

Be aware that just because it is "from a Mustang" does not mean that it is an 8.8. It could be a weaker 7.5 differential from a 4 or 6 cylinder.

8.8 cover:

http://ecx.images-amazon.com/images/I/41dRMOIss3L._SS500_.jpg

7.5 cover:

http://ecx.images-amazon.com/images/I/41ge%2BRGH6zL._SS500_.jpg

Additionally, if it was factory equipped with 5 lug axles it is '94 or later. These are wider than the Fox body rear which is usually preferred for the roadsters if the builder intends to use wide tires on standard offset wheels.

Finally you'll want to determine if it has TracLok limited slip or is an open diff. The TracLoc will have a clutch pack and big "S" spring in the ring gear carrier.

Jeff

[edwardb]

My 3.55 gear set had the ratio cast into the ring gear. You can see it here. This picture also shows the TracLoc Jeff mentioned.

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