How to inspect posi?

[Peter]

hey found a 3.73 7.5 posi for a decent price at 200 dollars and I am probably gonna go take a look at it. I was just going to pull the cover, make sure its a real posi and not welded spiders. no metal shavings, anything else i should look for?

 

[pontiacgp]

other than metal in the oil and broken or chipped teeth you can tell too much without disassembling it. You can check to see it it's an Eaton which you'll see the tabs from the clutch pack in a keyway to identify it and if there are no clutch packs then it's an Auburn with cone side gears. The Eaton can be rebuilt the Auburn cannot.

 

[Bonnewagon]

With the cover off, work the pinion back and forth and see how much backlash there is at the ring gear. A little is OK, a lot is not, indicating a lot of wear. Obviously look for chipped teeth, oil leakage at seals, and if it's a GM gear set, the part # and the tooth count of the ring and pinion (41-11 for 3:73) will be stamped on the outer edge of the ring gear. Wipe the oil off to see it, and if not, it's an aftermarket gear set.

 

[Peter]

were any auburns or eatons used in any factory applications? or is it just gm style which is similar to the eatons?

 

[pontiacgp]

gm never made any posi carriers, eaton and auburn made the carriers for gm

 

[Peter]

the sellers states the rear was out of a monte SS, now I don't know the year and I don't know how much the seller knows but i believe the montes sometimes had 7.625 rears. he hasn't specifically stated whether it was a 7.5 or 8.5 but at the low price it doesn't matter to me but I am safely assumed its a 7.5 or 7.625

question about the 7.625: are they naturally any stronger than the 7.5s. do they all have 26 spline axles?

 

[pontiacgp]

if it's a 7.625 it'd be stamped on the ring gear and ask him to count the splines on the side gears

 

[Peter]

I went to take look at the rear end which was advertised as a 3.73 posi in the ad. it became clear quite quickly that the rear was not at all stock and was not originally a posi according towards the stamping on the axle tube. after some research it turns out it has a 4.56 richmond gear set which was a little extreme for my taste but it was the right price for the whole rear end ($175) the axle has all new seals and was overall in really nice shape. the inside looked really clean with no metal inside and no chipped teeth. it seems some money had been pumped into this rear end.

I am not sure if richmond makes posi carriers? or there is another way to determine if is a gm posi or maybe an eaton?

 

[454cutlass]

with 456 you are not going to be able to drive it on the highway. but a good score

 

[Peter]

with 456 you are not going to be able to drive it on the highway. but a good score

i got a 200 4-r so it'll be interesting to see