Where to start?

[Shyguy]

Originally Posted by mrein3

No offense to shyguy but on a 1972 4x4, the crossmember under the transfer case adapter is the same for all factory configurations, manual or automatic.
GM made up for all the differences in the length of one transmission verses another by having a longer or shorter transfer case adapter. The adapter is the piece that holds the drive sleeve which is what couples the transmission output to the transfer case input. They also made all the 4x4 driveshafts the same length. So if you are switching from a 3-speed manual factory configuration to a 4-speed manual factory configuration you use the same driveshafts and crossmember. The transmission, adapter, and transfer case are changed. Same when switching from a manual to a th350. You swap out tranny, adapter, and t-case and use the same crossmember and driveshafts. I have personally done this swap and can attest to this fact.

I don't know why but GM had two different input shafts on the factory t-cases. ALL t-cases originally behind a manual tranny have a 10-spline input shaft. The t-case the General put in behind a th350 has a 28 spline input shaft which matches the 28-spline output of the stock th350.

Now after swapping to a th350 and having to drive that rig on the highway I wish I would have put a 700r4 in there. The highway rpms are bad when going 70-80mph in rush hour traffic with a th350 and 3.73 gears in the differential. If you have 3.08s perhaps a th350 will be ok. If you have 4.11s FORGET about a non-overdrive tranny if you ever want to venture out on an interstate highway.

GM never built a 1972 4x4 with a 700r4 but if you start with a th350/adapter/t-case (factory option) and build up a 7004r for a 4x4 (no tail shaft) it will bolt to the th350 adapter but is longer. I haven't done it yet but folks that have done this swap have moved the engine forward the 1-2 inches the 700r4 is longer than the stock th350. This moves the engine closer if not exactly to where it is in a stock 2wd configuration.

I hope this helps.

Thank you for the information for the location of the cross member. Some day I hope to have a '72 4X4 and you comments are really helpful.