I have a Auburn posi PN 542041.

I also have factory GM 3.73 ring and pinion.

Is this carrier a 2 series unit? And Im pretty sure I will need a ring gear spacer?

The gears are factory so they must be 3 series.

Am I correct assuming I need the spacer? Can anyone point me in the direction on a good deal for one, advice for which install kit would also be helpful.

Thanks!

 

Contact DTS for the parts. They have very good installation kits and a good spacer for the 7.5 (if there is such a thing). As always, I recommend getting the correct differential or gears, but if you have no choice but to use these then the spacer might work. Most of the time a spacer is just bad news.

 

First question. Where did you acquire the limited slip??
Second. You will need to know what axle shaft splines it needs? Stock for 1987 were 26 splines.
Third. My opinion is this sounds like furball and you need to start with what is in the car now and go from there.

 

That part number is for a 2 series with 28 spline axles.

 

It is a 28 spline carrier, and will be installed into a rear housing from a 92 rs.

I stole it off ebay for 90 bucks, its brand new.

Ring gear spacer yes or no? Ive done research and heard of people running them with no problems using grade 8 bolts.

 

The best thing to do with this is to get one of the thick gear sets and forget about the spacer.

One of the problems with using a spacer is that the ring gear won't center on the differential case. There is a machined band around the case that forms a press fit for the ring gear. This is what centers the gear. Look at these pictures and you will see that the spacer eliminates this area and the ring gear will just float on the case with only the bolts holding it in place. The bolt holes have way too much slop in them to hold the gear centered, which means that the ring gear will have runout. This will cause all kinds of problems with the gear contact pattern and wear. Be sure to click on the pictures and look at them close so you will see what I'm talking about. This is a 7.5 Auburn differential in the pictures.


Without spacer.


With spacer.

 

A "thick" gearset would be a much better choice than a ring gear spacer. I'd suggest going with a new set of Motive gears. They make a "thick" series 3.73 gearset to fit the 2 series carrier, plus they're actually still made here in the U.S. A lot of the gear companies have been sold to Taiwan, China, etc., and lots of people have had major issues with the quality. Richmond and Precision Gear are also good quality. I used Motives in my last rearend build and they set up beautifully, nice and quiet!

 

Actually Motive is made in Italy, and I think Precision is out of business. Motive is a high quality gear. I have about 100,000 miles on the one in my truck and it is still working perfectly.

Looks like I was wrong about US Gear moving to China. Someone else checked with them and they claim that they are still manufacturing their gears in Chicago.

 

Heh, you're right, I stand corrected. In fact, now that you mention it, isn't Motive associated with Masiero(spell check), the ones who make the high quality gearsets for the old Muncies? I know Reider Racing used to deal with Precision Gear, but it's been a while since I've been to their site, so maybe they have gone under by now.