Prop shaft balance

[rbonnett]

I'm pretty sure my rear prop shaft is out of balance. There's a rumbly vibration from under the back, especially at some speeds and on overrun. I pulled the tunnel cover and middle seat panel and drove around for a while. Its definitely from further back than the gearbox/xfer case area.

I know there are lots of things that can cause vibration, but there is a reason I suspect the prop shaft. When I bought this truck, it was delivered by the PO on a car dolly. He took the rear prop shaft apart and removed it from the diff when he towed it and replaced it when he got here.

I took it off at both ends and cleaned it up but don't see any sign of alignment marks anywhere. I've tried aligning the flanges both ways around, and also tried offsetting them 90 deg. each way. The vibration remains, though it is better or worse with some alignments.

I have pulled, pushed, yanked etc. checking for other things. I can't get any play in the U-joints or diff other than a small amount of lash in rotation.

Right now I have it back the way it was when I started. Short of trying every possible way of mating the 2 halves I don't know of any way for me to fix this. I'd like to avoid spending that amount of time if I can. Does anyone know of a shop in the Portland, ME area that can rebalance it for me? Any idea how expensive this sort of work might be?

Thanks

[Broadstone]

I had the same problem as you with the vibration and noise. I swapped mine with a used one that was with some parts I got from another truck and it was fine. Its wear on the u-joints and possibly on the splines of the shaft, if they all have a little play it all adds up to a big problem.

[SafeAirOne]

If you have ruled out the rear diff, then I'd swing down to your local auto parts store and spend the $20 (total) and put some new universals on and check for rumble/vibration again. If you still have the issue, take the shaft down to the local driveline shop and have it examined and balanced. They'd likely put new u-joints on to balance it anyhow.

Did you say that the PO disassembled the shaft for towing? Usually folks just disconnect both ends from the diff/transfer case respectively, in which case I don't think it matters which way you put it back on as it won't affect the balance of the system. Yoinking the slip joint apart on the other hands could be a problem...

[rbonnett]

I'll give the universals a try. Yeah, he took the shaft apart. When I removed it the nuts at the e-brake end were siezed so bad I destroyed 2 of them getting them off. I expect that's why he took it apart in the first place.

[Terrys]

very close to the splined joint, there will be an arrow stamped on each half. They may be hard to see without a good de-grease, but they are there.They must point to eachother.
Also, inspect the inner edge of the cups of both U-Joint. The boots will become torn and evidence of roller pin loss. Many times, merely checking a U-Joint by hand doesn't reveal a failing joint. Provided that all 8 snap rings are there and fully seated home, there should be NO movement of the yoke, side to side.

[LRMAN]

If you need a good machine shop in the Portland area I would go to Brackett in Westbrook. They do excellent work and know their stuff.

[rbonnett]

Well, its a new prop shaft for me. I started on getting the old U-joints out adn noticed there was some play in the splines. When I cleaned all the grease off, there were several places where they were chipped and worn. New shaft on its way fro our hosts.

I'm going to finish taking it apart and hang on to the flanges from each end. I guess there's no value to the shaft itself except holding the tarp down on my woodpile. I don't imagine the splines can be refurbished.

[SafeAirOne]

I don't imagine the splines can be refurbished.

No, but a driveline shop can re-tube it and put a new slipjoint on it. I think it'll rival the cost of a new shaft from our hosts though--I just looked at the costs of the proline shafts in the new RN News and they seem pretty reasonable.

Did you buy genuine or proline? Just curious about any quality differences...

[rbonnett]

No, but a driveline shop can re-tube it and put a new slipjoint on it. I think it'll rival the cost of a new shaft from our hosts though--I just looked at the costs of the proline shafts in the new RN News and they seem pretty reasonable.

Did you buy genuine or proline? Just curious about any quality differences...

I got the proline. The first 10 miles have been trouble free FWIW: There were no alignment markings on the new one when I got it - there are now. One thing I didn't like about it: the circlips and caps were painted over with the rest of the yokes. I don't know how much of a PIA that will be if and when I have to do the u-joints.

[HamptonAndrews]

Having what sounds like a similar issue on my ‘69 S2a SWB. See videos. Rumbling vibration at higher speeds on overrun (not in the video), and a new high frequency rattle at all speeds on overrun. See attached videos. Guessing there shouldn’t be any lateral play at the splined prop shaft joint right?
https://youtube.com/shorts/ciQjcnLda...aurmpIbgaIuWl2
https://youtube.com/shorts/7w8cSNkkG...bmX95h6iTnUxu9