M47 Transmission with rubber Flex Plate at front shaft. Does anyone know of a shop near Salt Lake City that has a balancing jig for this type of driveline?

Pretty much any 4x4 specialty shop can do it but...

Unless you are mixing and matching front and rear shafts from different cars, the shaft is balanced at the factory. If you did not mark the flanges when you disassembled, then first you make sure the u-joints are in phase. It should drive with very little vibration at that time until you hit a harmonic/resonate speed...is that the case?

Yes, Onkel Udo (Deutsch sprachig offensichtlich), I've retained the original shafts and they had been scribed and paint-marked for alignment at the factory.

A driveline shop recently helped me replace the Flex Plate, Carrier Bearing and Mount, and both U-Joints. They took care to mark the flange for alignment. Orignial flange bolts were reused. They do not have a jig to accomodate the Flex Plate.

The vibration is similar to what you describe, except it seems fairly constant. It causes a mild buzzing, tickling sensation at the pedals, shifter, steering wheel. A person driving the car for the first time would probably not notice, but having driven it for over 20 years I notice the change. There is a chance the vibration is originating from something else (motor), and I'm feeling it now that the driveline is stiffer and not absorbing the movement. I also replaced the soft transmission mount recently, creating a stiffer system.

I've been told the factory U-Joints are "crimped" or "staked" in place, and replacing them with clip locks might create enough imbalance for vibration.

I have called a few other shops with no success. I will try 4x4 shops. At this point it's looking like I might need to send out of state for balancing.

I agree with Onkel Udo

I agree that this is prob NOT a balance issue. If the shop reassembled the driveshaft as marked in disassemble, there cannot be a problem with the balance.

You are chasing the wrong tail, so to speak.

1) Were the new U-joints --- you mentioned the CirClips v some other "factory system" They are all CirClips"
Were the new inslalls jammed in by the shop... so they are binding?

2) Was the Flex coupler --- aka the Guibo, oriented properly... there is a Front and a Rear

3) You said you also replaced the sagging tranny mount. Are your motor mounts also oil soaked/old/cracked/etc.

Odds on NOT a balance problem.

PS I've had an 87 M47 (bought used) since 1997.

PS
I just bumped up my earlier post...long shot, but should be considered.
Is your new Center Support Bearing "fake" and the cause of the noise?

The Dangerous Game Behind Fake Ball Bearings

https://www.brickboard.com/RWD/volvo/1639311/dangerous_game_behind_fake_ball_bearings.html


One Tuesday morning last April, a blonde woman from Sweden stood out from the crowd, leading nine Kenyan officers to a storefront she believed was selling counterfeit goods. But they weren’t after knock-off handbags, watches or sunglasses. The shop specialized in a far less sexy -- and ultimately more dangerous -- fake product: ball bearings.

Overseeing the raid was Tina Aastroem, head of brand protection for SKF AB, a Swedish maker of bearings. Aastroem had cased the store six months earlier, concluding that many SKF products there, as well as those of rival manufacturers FAG and Timken Co., were fake. In the raid, her team spent hours sorting through boxes stacked from floor to ceiling--fueled by chicken ordered from the local KFC--and found $100,000 of counterfeit bearings for cars and other vehicles.


http://www.bloomberg.com/news/articles/2016-10-13/forget-sham-rolexes-the-real-money-is-in-fake-ball-bearings

If it is fairly constant...that does not speak imbalance to me but it could be. I would be more inclined to believe it was u-joints out of phase, tranny tailshaft bushing (except I think it is bearing on the M47 and know it is on the M46) or something else.

I have honestly never heard of of balancing with the Giubo in in the mix...and that is for BMW, Volvo or anyone else that uses one.

UOII is correct about having the u-joints in phase--and with regular driveshafts using 3 u-joints that leaves only one of two positions that could be in "factory balance" (assuming both halves from original). With the flex disc at the front that method doesn't apply so if the two halves are original and the orientation wasn't marked, "visual" alignment may involve a number of visually correct but not "in balance" solutions. I don't have much experience with the flex disc system so never had to take into account how the disc sits when the rear half u-joints are rotated so the "crosses" are parallel and vertical to the ground. It does seem like the original poster does need to find a shop to balance the works. As suggested a 4x4 shop--or a truck driveline specialty shop should be able to do the job. -- Dave