Best way to retain viscous coupler on 5-speed A750F conversion?


Aug 21, 2012
Northern Nevada
This is one of the last details I need to sort out before I dive into my engine and transmission conversion. I would like to retain the viscous coupler function while using an A750F 5 speed transmission on an 1HD-FTE. I’m looking for guidance from the community on how best to accomplish this?

The A750F has a shorter nose cone and I believe an open transfer case differential since it’s electronically controlled whereas the 80 series transfer case uses the mechanical viscous coupler. Is it possible to just bolt and 80 series transfer case assembly onto the A750F or am I going to have to find some combination of output shaft and/or input gear in order to mate these two together? Has anyone been here before me?

I have a spare A343F gasser transmission and transfer case sitting on the garage floor so I can begin to tinker but before I crack anything open, I thought I’d ask first.
I look forward to your comments and thanks!

Lutz Auto

Supporting Vendor
Jan 26, 2015
You can mix them together easily. I used the A750 transfer case and the rear half of the A343, but I only did that because the A750 case had less miles on it and I was being cheap. If I were to redo it, I would have just refreshed the A343 TC and used it.

The A343 case fits the tunnel better. There is some debate about whether the the input splines are the same or not. Unfortunately, I didn't count them, but I did verify that you can swap the input shaft from on TC to other if you end up needing to. They are easy to work on and parts between the 2 are pretty much fully compatible.

There are some measurements to make for shims if you end up mixing the 2 together like I did, but it's not complicated.

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