I was getting ready to install a rear 8.8 differential in my 1993 Bronco when I noticed that the shock mounts on the new rear axle were facing to the rear instead of the front. This was a junkyard rear axle I've had sitting around for a couple of years and it was supposed to be out of a Bronco although a F150 should have been the same. It is an 8.8, has the anti-lock trigger gear inside, has the electrical plug on top, and is new enough to use the flat pinion flange for the drive shaft. It didn't come with the sway bar but I was going to unbolt that from the old and transfer it to the new.

I have the rear out of my 93 and was in the process of changing some parts from the old one to the new one when I noticed the difference. The new differential has the shock mounts facing the rear while the 93 has them facing the front. I looked at my 91 Bronco as well as the rear that came out of my 91 and all three rears, the 93, 91, and the one that came out of the 91 all have front facing shock mounts. What differential do I have?

 

I believe I've solved the mystery. It looks like this rear is from a newer truck, maybe late 90's. I just noticed the lugs have a courser thread than the 1/2-20 size on my other Bronco's and when I checked a 5.5" pattern drum from the 93 against it, it had the smaller (approx: 5&3/8") metric bolt pattern. I saw the Bronco it was supposed to come from but maybe they had this one out and thought it was the same. Either way it's way too late to take it back. I guess I can use the gear set from it to rebuild one of the other differentials.

 

is the WMS to WMS the same on both your current rear diff and this mystery diff? Perhaps it came out of a Van or a 97 F150 running the metric bolt pattern.

 

The brake backing plates are a couple inches farther apart as are the perches for the leaf springs. I think it probably came from a 97 or newer F150.

 

yea i figured, the R&P probably isnt the same either. I think the 97 trucks was a larger 9.75 ring an pinion or something like that.

 

I looked at the ring gear to see if it was a 3:55 and it was, I didn't check the diameter.