Driveline noise

[brentwood]

I have a 72 j4000 that I bought with a 2wd Chevy driveline. Since it ran well, I had my friend install a divorced Dana 20, custom cross member and driveshafts.
It starts up, runs well, shifts in and out of 4wd but has a bad driveline noise that gets worse as rpms increase. Sounds like a whining noise and maybe a friction type noise. It actually caused a vibration when up on lift, but no vibration when on ground.
When we had it up on lift, in gear, it seemed like vibration was coming from transfer case.
I bought another Dana 20 and still same issue.
I'm thinking maybe the short shaft from trans to transfer case is at a bad angle or something with the divorced adapter isn't quite right. Don't want to keep wasting money guessing.
What do you guys think?

[J20 project]

Hmm, while I really have no doubt that if that unit was in my care.....I could figure it out. But 2 things stand out. 1) I have never seen a divorced Spicer(Jeep ) 20, much less 2 of them.. so interesting at least. 2) divorced cases are typically set up in line...straight, no angles and if that is what you have welllllll good luck, and maybe your ace mech is not so ace........3) oops 3...did you have quality driveshafts built or some redneck "it'll work" junk.....?



Actually trying to help, but I do that by challenging peoples' thought processes.....

J20....I build shafts and drivelines for a living,,,,been wrenching on these es for 45 years....

[brentwood]

Hmm, while I really have no doubt that if that unit was in my care.....I could figure it out. But 2 things stand out. 1) I have never seen a divorced Spicer(Jeep ) 20, much less 2 of them.. so interesting at least. 2) divorced cases are typically set up in line...straight, no angles and if that is what you have welllllll good luck, and maybe your ace mech is not so ace........3) oops 3...did you have quality driveshafts built or some redneck "it'll work" junk.....?



Actually trying to help, but I do that by challenging peoples' thought processes.....

J20....I build shafts and drivelines for a living,,,,been wrenching on these es for 45 years....

1. The original used Dana 20 I bought came with a divorce adapter already installed. Novak and some other companies made divorce kits for the Dana 20s. So I used the same divorce kit with the 2nd Dana 20.

2. Nobody said my friend is an ace mechanic and he doesn't own a driveshaft shop if that's what you're getting at.
The short shaft is centered width wise under truck, but a little off height wise. Would a double cardan joint help this?

3. He set it up so front and rear driveshafts are the same length. He made one, and the other was made by professional shop. It made no difference with issue which one was in rear.

4. So should I be looking into the divorce adapter or the short shaft (trans to case)? Or something else I'm missing?

[J20 project]

Actually, assuming you have a short shaft th400...which your truck would have had if auto when new.....I would just go back to oem configuration and bolt the tcase to the trans....
I know that would be reversing a lot of work but...

Also, what does your intermediate coupling/shaft look like? Most boats, etc will have a pair of 1310 type flanges bolted together...

Lastly, if the truck cruised w/ a single shaft in the rear okay, and the rear shaft professionally done...the issue is likely as you said,,,well sorta. The issue lives between the ouput of the trans and the ouput of the tcase, right?


J20.

[Carnuck]

Driveshaft out of synch front to back half?