posi traction for 68 Cat wagon

[badwgn68]

looking to replace my current cluster with a posi cluster in my 68 Cat wagon....need some help in finding out what big car years will fit.. want to replace my current 2.98ish ratio with a 3.23ish ratio ...any suggestions or help would be great..thanks in advance...Jeff

[Larry]

Pontiac has three ratio "groupings" for '65-'69 full-size.
A) 2.29/2.41/2.56
B) 2.73/2.93/3.08
C) 3.23/3.42/3.55/3.73/3.90/4.11/4.33

According to Hollander Interchange information you can only interchange internals within each group, not from one to the other. Therefore, to go from a ratio in one group to a ratio in another group, you need to replace the entire axle assembly, including its internals, from the next group.

I cannot find any info about going from a non-posi to a posi, but if my own experience is the same, it was possible as long as you are in the same "ratio group" already. But with the cost of that swap, including all the gear set-up work, it is best to just look for a complete posi assembly for one clean swap and be done with it.

From an interchange point, there are some Oldsmobile units that swap, but the Hollander info shows all Pontiac full-size from 1965- 1970 to interchange, so there should be plenty to choose from.

Let us know how this all works out.

[Guest]

thanks for the info...did a little more research ....there are codes for the posi rear ends.... the code for a 68 3.23 posi rear end is UT ....where would that code be located ?...also when you mentioned a complete swap over...is that axel's and differential or the whole rear end?..thanks ...Jeff

[Larry]

The UT code is for '67 Firebird 3.23 posi (locking), according to Hollander Interchange.

For '66-'69 the 3.23 posi is code VG. If you want to go a little lower, the 3.42 is VH.

Be sure to read codes carefully because the non-posi codes are UG and UH, respectively.

The letter codes are near the carrier according to the Hollander people, but that isn't very specific, for sure. So, I checked a '66 manual and it shows the codes on the rear of the "axle portion" of the differential, "near the carrier". They are quite big leters, so should be easy to find. In this case they were on the passenger side. Also check to see if the rear end cover plate has a "Safe-T-Track" tag on one of the lower bolts.

This swap would require the entire rear end-- housing and all internals. I'm quite sure your brake plates, etc. would still be the same, so save your old plates and brake assemblies if they are all still good.