Drive Shaft: ‘50 champion vibrations

[Flthdchamp]

Hello everyone,
I hope someone can help me figure out an issue I’m having with a vibration I’m getting when I exceed 25 mph. This just happened after I replaced the carrier bearing, support bushings and ujoints in my car. The carrier bearing was noisy and the ujoints were all missing their grease seals so I replaced them. I marked the drive shaft yokes and flanges and aligned the two drive shafts so that all zerks are pointing in the same direction.
Are the transmission yoke and slip yoke supposed to be aligned? Wasn’t sure if that mattered. Any tips on how to find out what the issue is?
thx,
Jim

[altair]

Remove the rear universal and rotate it half a turn and reattach it and see if that makes any difference. That will tell you if it is the shaft. It may require rebalancing.

[Flthdchamp]

Alright, will do, thx.

[Hugh]

There is a Studebaker service bulletin that applies to 50-51 cars directing to “dephase” the univ joints exactly as Altair states. It also describes the relocation of the center bearing mount. I had a clunk and vibration at speed and found the rubber mounts for the center bearing we’re worn as well as the holes where the rubber mounts go. To test, I wrapped the two rubber cushion mounts with a few turns of electrical tape so the rubber mounts were very tight to get into the holes. Vibration and clunk gone. I am with 51 Commander coupe with automatic. May not apply to yours but easy to check and test. Good luck. Hugh

[Flthdchamp]

Thx Hugh, good info! I replaced the bushings with new ones and the holes look ok. This vibration happened after I replaced the ujoints and carrier bearing. I didn’t have an issue before this. I didn’t realize that changing these things out could create a balance issue. I had performed the repair per the shop manual and thought it would be fine. Live and learn lol

[StudeRich]

Also, Note that there are several possible Mounting Holes in the Crossmember to mount the Center Support bearing, so make SURE they are where they were previously.

[Flthdchamp]

Thx Rich, I didn’t realize there were more than one set on a 50 champion?

[Hugh]

I believe the multiple mounting holes in the crossmember were installed at the factory after about Feb or Mar of 1951. My 51 does not have the holes, but the bulletin instructed that additional mount holes would be drilled 1/2 “ above the originals in the crossmember. After a certain s/n there would be three mounting holes on each side of the center bearing mount holes. I honestly don’t know when or what s/n was the cutoff, sorry. I really don’t know if this applies to automatic or manual or both. I do know it helped my 51 Commander with automatic. Possibly dephasing the ujoints could solve the problem. Please keep us up to date. Hugh

[Flthdchamp]

Hi guys,
update- there are only 1 set of holes to
mount the carrier bearing. I rotated the rear driveshaft ujoint 1/2 turn. In some ways better but still not right. I
may bring the whole assembly for balancing.

[Hugh]

Not to be “crying wolf” but it’s simple to remove the rubber mounts and wrap with electrical tape to get really tight and reinstall. Mine “felt” tight but the tightening with tape really made the difference. Have a new bearing support piece and will change during hibernation Sure hope you can correct without having to balance the shafts, but balancing may be the solution. Good luck. Hugh

[Flthdchamp]

Thx Hugh, the carrier bushings were fine previous to my replacing the bearing and ujoints. I had no vibration at all then. In fact, there was less vibration when I put the old bushings back on today but still something wasn’t right. I elected to have the driveshafts and joints checked out at a local driveshaft shop. I’ll let you know what they find. I appreciate your advice

[Dan Timberlake]

When installing u-joints on some styles with pressed ( not clamped) caps it is easy have a very tight ( resists rotation) joint if the caps are pressed in just a skosh below the snap ring.
I normally push the new caps out against the fully seated snap rings to ensure some end play for free rotation.
The new joints when fully assembled should rotate very easily.

Mechanically Tight u-joints are essentially a bent shaft that tries to crank the nose of the differential etcetera up and own and side to side once or twice per revolution.
If that is happening at 2 rpm imagine what it is like at 2000 rpm. The rubber center support bearing and rubber axle mounts are designed to block a lot of noise and vibration from the passengers, but they can only do so much.

I'd check for visible motion when rotating the drive shaft by turning one wheel jacked in the air ( open non TT diff) .
By rights the runout of the driveshaft tubing when rotating should be only the runout of the tubing and how it is welded to the yoke.

Good quality driveshafts should have something like .010" TIR maximum lest heroic compensating balancing be sent to battle after the fact.

[Flthdchamp]

Thanks Dan, I get the driveshaft back today from the shop- I assume if/when they balance it that they check for runout. I’ll ask what they found.
Does the position of the carrier bearing on the front shaft or tightness of the grease nut have any influence on vibration? Right now I’ve got the grease nut tight but when I disassembled it I noticed the grease nut was just “snug” and easily came free when I removed it. I was wondering if that or carrier bearing position could influence the movement of the slip yoke for the rear shaft and cause a vibration. There should be a certain amount of play, correct? The carrier bearing is currently spinning freely and quietly and snugly bolts to the crossmember so no issues there. I would think that slip yoke play was predetermined by the length of the shafts but wanted to double-check.
thx,
Jim

[Flthdchamp]

So I got the driveshaft back today- no runout but I found out what was the issue and it was my error! 1 needle bearing was missing from one of the cups. I’m doing this job on my back with a shop light in my garage and missed it! Sorry I wasted everyone’s time- I installed the driveshaft and the vibration is gone now , drives perfectly.

[RadioRoy]

Thanks for posting the solution. It adds to the knowledge base and rewards everyone who helped with the problem.