Randy_M

I think I have done my homework for this posting but I wanted to make one final try at finding a posi unit for a '92 Camaro, 28 spline, 3.08:1, 7.5in, 10 bolt differential. It appears that there are none available but if someone has knowledge of such an item, please point me in that direction. I prefer not to change the final ratio since I am really happy with the current ratio and the 5 speed manual. I realize there is not much difference in the 3.08 and a 3.23 so I might consider that as a last resort.

dmccain

iTrader: (2)

3.23 will have a different carrier. If you go aftermarket get an Eaton or Yukon Duragrip. Auburn units our cars are equipped with arent the best.

Randy_M

The problem must be the difference in the carrier housing which tells me I can't have either in my current housing. I have a 4th gen housing with open 3.42 gears. As much as I had rather not, I may have to swap housing to get to install the posi I want but with 3.23 gears. Double swap. Do you have any idea of the spline count on the 4th gen differential?

Fullmonte77

iTrader: (3)

4th gen are also 28 spline.

sofakingdom

iTrader: (1)

You have a great deal of confusion all mixed up into one giant blob of ... something.

There are 2 "series" of carriers in the GM 7.5" / 7.625" 10-bolt. The 2 series is for 3.08 and lower ratios; the 3 series is for 3.23 and higher. The difference is the location of the ring gear flange on the carrier. As I've posted so many times, the "ratio" is NOT ONLY the ratio of the gear tooth counts, BUT ALSO, the ratio of the gear diameters. So, since the ring gear is always the same size, as the ratio INCREASES, the pinion diameter DECREASES. (a 3.00 ratio pinion would be exactly 1/3 the diameter of the ring, a 4.00 ratio pinion would be exactly 1/4 the diameter of the ring, and so on) This means then, that the ring gear has to MOVE OVER closer to the pinion, as the ratio increases. The factory accomplishes this by making the ring gear thicker for higher ratios, up to a point at which it's so thick that it tends to warp during heat treating; at that point, they start a new carrier "series", with the ring flange moved over, and thin ring gears again. The difference between 2 and 3 series in the 7½" 10-bolt is about .400". (slightly greater than 3/8") While this model of rear has 2 sizes given for it (7.5" and 7.625"), they are in fact identical in every way, except that the OD of the ring is slightly greater in the one. GM introduced this rear in about 77 and enlarged the ring in around 86 or 87. Either will fit in any rear of this model. I don't think any are even made anymore in the smaller diameter.



2 series on the left, 3 on the right. Note how far the flange for the ring gear is from the bearing: the 2 series flange looks flat while the 3 series looks like a cone. These are both Auburn: the one on the left is a 3rd gen car's stock one, the one on the right is an aftermarket "performance" one (the same excrement, really, just with more clutch pack springs to make it chatter more going around corners) from the mid-90s some time. The one on the right was mine; it being a steaming bucket of elephant plop, aka Auburn, I gave it away. I have too much conscience to take money for such garbage.

If you have 3.08 gears, then your carrier is 2 series. The reason you can't find a new posi for it is because nobody wants that crap. Everybody wants to get rid of crappy gears like that; anybody in their right mind buys a 3 series carrier and better gears.

The ONLY reason you're "happy with" the $hitty 3.08 gears is because you've never had anything better in the car. While it's absolutely true that TPI's complete and total lack of upper RPM capability means that it's SUUUUUPER EEEEEEZY to put too much gear behind it, that doesn't mean that it can't benefit from SOME degree of uncorking. After all, the "best" of the 5-speed TPI cars (5.0 w/ G92) came with 3.42 or 3.45 gears, and those are a YYYYYYYYYUUUUUUJJJJJJJJE improvement over the base-model 3.08.

Your car has 28-spline axles, so any carrier that fits a 4th gen will also fit your car. There is no difference in the "housing". However, your axles are almost certainly worn out like everybody else's, and whether or not, they are still crappy stock butter metal. Aftermarket ones are NIGHT & DAY different, like replacing a zamac propeller on a boat with stainless steel.

In 2024 I would NOT use a clutch-type posi like an Eaton or Yukon. While those are certainly good-quality products, which I myself used to recommend (and for that matter I have an Eaton in my own car that's been there for 25 or 30 yrs now), and in fact the Eaton was the unit that GM invented the trademark "PosiTraction" (now shortened to "posi") for back in the 60s, it's 2024 now, not 1974. Lots of things have changed in the last 60 years since the Eaton was introduced. Use a worm-gear type such as a TrueTrac or Torsen. Costs about the same, has none of the problems that clutches cause.

I'd strongly recommend a gear ratio change to 3.23 or 3.42, all new bearings, a crush sleeve eliminator spacer, a carrier and set of axles as described, and a "girdle" type of cover such as a T/A Performance one. Also, have somebody straighten the tubes in the housing and weld them up all the way around, and fill in the plug welds the factory used which are almost certainly cracked and leeeeeking like everybody else's; weld on a pair of LCA relocation brackets; and take it to the powder-coating shop afterwards. If your car has drum brakes (I doubt it but the topic must be covered), don't bother doing this without also doing a rear disk conversion, to some one of the 89-up PBR systems. (NOT the 88-back Delco-Moraine type with the crappy cast-iron calipers)

Tom 400 CFI

I totally