8.5 posi unit...

[BLACK MAGIC RACING]

Will an 8.5 posi from a caprice fit the tr housing and axles? anybody ever make the switch?

 

[GNVAIR]

You would have to find an 87 and earlier 8.5 for the carrier as the 88 and laters have 30 spline axles where as the earlier ones have 28 spline. No other GM vehicle has axles that will interchange. The best place to find a posi carrier is a 71-81 F body (mostly Trans Ams and Z28s) as long as it has a 2.73 or numerically higher ratio.

 

[Red Regal T]

Originally posted by GNVAIR
The best place to find a posi carrier is a 71-81 F body (mostly Trans Ams and Z28s) as long as it has a 2.73 or numerically higher ratio.

Adding to the good info above, if the unit has a numerically lower gear ratio, you can buy a ring gear spacer from summit and be able to use it with no problem. I've been beating on the one in my car for the past two years and 40,000 miles. Came out of a 76 TA.

 

[GNVAIR]

I wouldnt want to run a car on slicks with a spacer and longer bolts. I could show you a pic of what happens. Not a pretty sight.

 

[BlackBeauty]

Originally posted by GNVAIR
....where as the earlier ones have 28 spline. The best place to find a posi carrier is a 71-81 F body (mostly Trans Ams and Z28s) as long as it has a 2.73 or numerically higher ratio.

Old thread brought back to life..... how can you tell if it has 2.73:1 or higher (numerically) gears? Did they come in certain models only, or...?
And, do all '71-'81 F-bodies have posi?

 

[carguykeith]

One thing to watch when getting a carrier out of an F body is that some (I think the ones with rear discs) do not have provisions for c-clips!!!!!

I had the option of either taking everything apart and having the reliefs cut in the spider gears or adding c-clip eliminators. I did the later, but be prepared for a larger than expected project if you are expecting to just change and reshim the carrier to have a posi.