Tallest transmission tunnel?

[77 K20]

I had a shop install my magnum doubler in my '77 K20 probably 2 years ago... should have done it myself. They used 2" square stock to drop the transfer case/doubler down from the frame. I don't like this. I have a rear driveline vibration now. Have to tilt the rear axle pinion down or raise the transfer case back up where it should be.

I removed their 2" drop and replaced it with some 1.4" spacers. This helped my driveline vibration a bit. Can't bring the transfer case up higher- as the 205 would hit the transmission hump.

Is the late 70s 4x4 automatic transmission tunnel the tallest one out there? Any aftermarket one that are taller?

This would probably be the best option. I was also thinking of ORDs 1" bodylift but am not a fan of bodylifts. I also have a 5th wheel hitch I'd need to get spaced up also.

I also removed the second crossmember and the skid plate as they just bolted it on with one bolt to a bracket for the gas tanks.

 

[nvrenuf]

So you’re running a Magnum/205? Is the 205 clocked up any?

If your cab is originally a 4wd cab then you should have the tallest tunnel. I have a 203/205 Doubler with the 205 clocked up 2” and while mine is close it doesn’t touch the floor.

Get rid of the tcase crossmember spacers completely. Lowering that crossmember can improve the rear driveshaft angle but it hurts the front. Put the crossmember back flush to the frame and correct the rear pinion angle. If you still get a vibration you may have to go with a double cardan joint at the tcase.

 

[77 K20]

The 205 was clocked down a bit to lessen the driveline angle for the front driveshaft. With ORDs leaf springs when the front axle is dropped out it was a bad angle for the U-joint at the front diff. Having never had a 205 before this one it is kinda hard for me to know exactly. Here is a pic of the current orientation.

After putting in smaller spacers I drove my truck to work. The Magnum popped into neutral when I slowed down to turn in to work. Sounds like the linkage is hitting the body somewhere. I'll have to crawl under and look more closely.

If I can raise the crossmember back up to the frame and remove the spacers completely I'm pretty sure that will fix my rear driveshaft angle. I do already have a double cardan joint at the transfer case (new front and rear driveshafts from Tom Woods).