Drive line vibration??

[streamer]

I just started driving my '48 after puting it all back together. It has new universal joints installed, but has a very bad vibration at 20 to 30 mph. Even with the clutch in or in neutral coasting the vibration is there -- less at higher speeds, but still too much. I tried rotating the drive shaft 180 degrees to make sure that the front and rear yokes were aligned, but the vibration is still bad. I also checked the motor mounts -- all good and all tight. I know there were some threads about this subject and I did do a search, but found very little information. Help is needed!! Thanks

[Jerry Roberts]

Have your tires been balanced ? Is there a tire out of round ? Is there a tire coming apart ? A badly bent wheel ?

[grey beard]

Streamer,

Your description of the problem sounds very much like a drive line problem. If you still feel it in neutral, you have eliminated the motor and trans. I would look to the prop shaft. Get it up on jack stands under the rear axle and watch the thing turn at low speeds. The drive shaft should look perfectly straight when it is turning. Any run-out you can see is likely your problem.

Old fashioned in-ground hoists in many older shops had a fixed yoke plate on top of the piston. When veheicles were raised on these older frame contact hoists, the rear axle hung down till the shocks stopped it's downward travel. Sometimes this allowed the prop shaft to hit the yoke, and the weight of the rear end would bend the shaft. I used to own an interest in a salvage yard in NJ. We sold lots of drive shafts to shops that had this problem.

If your shaft is bent, look in your yellow pages for a drive line shop. They can re-tube a shaft without too much expense, unless you can find a used one on this forum. JMHO

Good Luck

[streamer]

Streamer,

Your description of the problem sounds very much like a drive line problem. If you still feel it in neutral, you have eliminated the motor and trans. I would look to the prop shaft. Get it up on jack stands under the rear axle and watch the thing turn at low speeds. The drive shaft should look perfectly straight when it is turning. Any run-out you can see is likely your problem.

Old fashioned in-ground hoists in many older shops had a fixed yoke plate on top of the piston. When veheicles were raised on these older frame contact hoists, the rear axle hung down till the shocks stopped it's downward travel. Sometimes this allowed the prop shaft to hit the yoke, and the weight of the rear end would bend the shaft. I used to own an interest in a salvage yard in NJ. We sold lots of drive shafts to shops that had this problem.

If your shaft is bent, look in your yellow pages for a drive line shop. They can re-tube a shaft without too much expense, unless you can find a used one on this forum. JMHO

Good Luck

I put the truck up on jack stands and ran it up to 25 mph in 3rd gear all of the "hop" seems to be at the front yoke. The universals have less tha 75 miles since new, but there is some up and down play as well as side to side. The rears are nice and tight with no play. I noticed that shaft sleeve yoke has been hammered in a couple of places and I don't remember having lined up any reference marks when I put it back together after the universal joint instalation. I guess I'll replace the front joint and look for reference marks on the drive shaft and the yoke. BTW when I ran it up to 25 mph the same vibration that happens on the road was there. Any other suggestions? Thanks

[grey beard]

Did you have the slip yoke off of the drive shaft? If you did, it has to be reinstalled on the splines in phase with the rear u-joints. That means that the two stationary joint eyes must be parallel. If they are off even just one spline, it will do exactly what you are experiencing. Sounds almost like your front and rear U-joints are out of phase. Check it out and let us know.

When I did my U-joints, I had trouble getting the front slip yoke to come apart. Do you know what holds these two splined pieces from coming apart?

Good Luck

[streamer]

Did you have the slip yoke off of the drive shaft? If you did, it has to be reinstalled on the splines in phase with the rear u-joints. That means that the two stationary joint eyes must be parallel. If they are off even just one spline, it will do exactly what you are experiencing. Sounds almost like your front and rear U-joints are out of phase. Check it out and let us know.

When I did my U-joints, I had trouble getting the front slip yoke to come apart. Do you know what holds these two splined pieces from coming apart?

Good Luck

I got the yokes lined up perfectly and reinstalled the u-joint -- I can do it in ten minutes now! Started the truck and ran it up to 25 mph, big vibration and the rear axle is making noises like it has a bag of hammers inside. Took it off the stands and drove it down the road. Vibration starts at 25 mph and pretty much stops when she gets to 30 and above. I am now thinking of a rear axle swap and would like to use a more modern axle that will pretty much bolt right in. I did several searches, but I could not find a list of rear ends that bolt up to my '48. I noticed that you had some posts in a couple of the threads I read, so maybe you can steer me in the right direction. Thanks

[grey beard]

Mr. Streamer,

Don't know if you are contemplating a differential swap into your old housing or a completely different rear end. A lump from an automobile usually has a higher ratio - very desirable from my view point - and a complete rear end swap usually carries with it later and larger brakes. Your choice.

I suggest you spend some time reading archival posts on this forum. Ovre the past four years I have read every post on every archive beginning with the Mayflower, 'er whatever and whenever they began. You will learn bunches.

A gent with the handle of "woodscavenger" has a Jeep rear in his Piothouse, and several others on the forum have performed simiilar swaps. Check these guys out, do some searches, and make your decision.

This forum is sorta like the Bible - every time you read it you learn something new. Use the search function, play with key words in your searches and see what you get. Lotsa' stuff here, especially in the archives.

Good Luck

Let us know what you decide.