Acceleration vibration on '58 Imperial

[Gregg Benedict]

I just recently got my '58 Imperial back from the shop to do some ignition and brake work. It now has a vibration and "thumping" on moderate to hard acceleration, mainly from a stop. It sounds like it is from the drive shaft, possibly hitting the floor. It smooths out when letting off the gas. If it is from the drive shaft, it may be the center bearing, but I'm not sure. Several mechanics working on it cannot find where the vibration and noise is coming from. So, what is everyone's thought on this? If it is the center bearing, where can I get a new one?

-Gregg B.

 

[CBODY67]

Check all of the u-joints in the driveshaft, including where the front yoke goes into the tail shaft housing. There is a bushing in there that can wear and cause the rear seal to leak a bit.

CBODY67

 

[57fury440]

If the noise was not there before the work was done, then I would check the brakes. You said you had some brake work done. maybe something came loose and is rubbing.

 

[CBODY67]

IF there is as much space under there as I suspect, nothing is "rubbing" per se, just a harmonic that is happening. Was the complete driveshaft removed or just the front section of it? If at all?

If something is really hitting something, put a jack under the middle of the rear axle and cautiously put the car in "D" and raise the road speed to seek to duplicate the sound. That would maintain the ride height for the rear wheels and chassis, rather than having the rear wheels dangling and driveshaft angles different than when at ride height.

Just some thoughts,
CBODY67

 

[Gregg Benedict]

Nothing was done by the mechanic to the drive shaft or rear end. The more I'm thinking about it, I'm not sure it has anything to do with the driveshaft at all. It only happens when accelerating from a stop, and only up to about 20 mph or so. After then the vibration and thumping go away. Up to that speed, the driveshaft wouldn't be turning that fast anyway, yes? Could this be something in the transmission?

 

[david hill]

Check out the following center carrier mount and bearing, stuck or frozen slip joint, damaged or sticking u joints and broken rear trans mount.

 

[65Port]

You're going to have to get under there to get a better idea. Can only speculate so much. I would get it up on jack stands and reproduce the problem. You, or your helper can be underneath checking things out. Have you tried putting it in neutral and then revving to 2k or so to see if the noise is still there? Could be a cracked flywheel. Happened to me.

 

[mr gtx]

check your exhaust system.

 

[CBODY67]

The most likely place the exh system might "touch" is the upward and downward bend over the rear axle. If more toward the front, more unlikely, but there could be a place the past location was changed if new motor mounts were installed when the engine was out. ESPECIALLY if a "muffler shop bent" pipe was installed sometime in the past.

Just some thoughts,
CBODY67

 

[Gregg Benedict]

I got around to finally checking out the driveshaft and the carrier bearing. It most definitely is the carrier bearing. There is about 1/2" of play in the rubber "donut" in the bearing housing. All the other components seem tight. So, my first guess was right. As far a fixing it, I am going to try using some modern parts and a homemade adapter plate as a first option. Then, I can have the other one sent out and rebuilt. Unless someone happens to have a spare center carrier bearing (good or bad needing a rebuild) for a '58 Imperial that has a standard non-x-member frame (2-door Hardtop or 4-door sedan)?

 

[Gregg Benedict]

And, it's fixed! After talking with someone on the Imperial Mailing List site, I found out there is an aftermarket carrier bearing assembly that can be slightly modified and used with a custom made conversion plate to be used as a substitute. The person I talked to used this to convert his '58 Imperial 4-door Hardtop (which has a large X-member frame). Some said there were a couple different carrier bearings made, depending on whether the model had this X-frame or not. From everything I read, there was only one type of carrier bearing made for all '58 Imperials This kind of proves that. My '58 is a 2-door hardtop and does not have the X-member frame. Still, this same conversion plate worked perfectly in terms of height and offset.

P.S.: I was going to get the original bearing fixed professionally by sending it off, and using it as a backup. However, after noting how much more robust this conversion is, forget that!