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MG MGA - Drive train vibration

Well as I work out the little problems I discovered that at 45 MPH I get a lot of vibration from the back end of the car. If I throw it into neutral at 45 I still get it which eliminates the motor and gearbox. Do you think maybe my new rear "U" joint is faulty? I do remember having a tough time installing it!
Bill R

If you had a "tough" time installing a u-joint it could have been damaged by installation. U-joints should install smoothly. What type of shaft do you have? If the 1600 type is slipped together out of time it can cause a vibration. Most driveshaft vibrations are speed related getting worse the faster you go.
My first step would be putting the car up on a hoist and having an assistant run it up to speed and observe from underneath. Look for tires that are out of round, bent wheels or a wobble in the driveshaft. Were the tires balanced?
Any good driveshaft shop can check or balance a shaft.
R J Brown

Thanks RJ, I have the 1500 and recently had all the new tires and Dayton wire wheels ballanced and re- checked, along with adjusting the tie rod ends on a rack. So I am going to cross those off the list as potential culprits. I own a parts car so I may just grab that shaft and two new U joints and go from there.
Bill R

Bill

2 U joints? Must be a late 1500 so the comments on the 1600 shaft are applicable.

HTH

Larry

58A
Larry Hallanger

I once had faulty u-joints. They were from one of the usual suppliers but I can't remember which one. They were a bit undersized from end to end. The caps did not fit tightly to the center piece when installed. This caused a vibration. I replaced them with u-joints from my local auto parts supplier and have had no problems since. I'm reasonably certain this was a one-time deal as I have never heard of this happening to anybody else since.

Chuck
Chuck Schaefer

Early 1500 also has two UJs, one front by the slide-on shaft, one back by the banjo
dominic clancy

did you put the drive shaft back on in the same orientation that it was originally?

That can effect the vibration.
T McCarthy

T.M, with all due respect, I don't see how the drive shaft alignment to the flanges should matter. If there are 2 U-Js then what matters is that the front and rear joints are correctly aligned to themselves. Each U-J creates a non- uniform rotational transmission when it is "bent" and the second UJ if aligned correctly, cancels it out with the effect of uniform motion overall. It should not matter whether the joint flange is mated to the same holes as it was detached.
Art

Just as a test, why not switch wheels front to rear? If the vibration goes to the front, Bob's yer uncle. Can't hurt to try it out, and may save you unnecessary repairs.
Tom

Tom, I did rotate and re-balance the tires. they are new Dayton rims. I really feel it is more in the drive shaft or worse case, my rear. What type of company would balance a drive shaft? A transmission repair place ?


WMR Bill

Art, you may well be correct.

All I'm aware of is that the workshop manual goes out of its way to tell you to mark the shaft prior to removal and to put it back in the same orientation.

Tysen
T McCarthy

Bill

Just putting my lateral thinking hat on. Did you by any chance paint the prop shaft while you did the UJ replacement? It has been known for the weight of paint to throw the propshaft out of balance.

Steve
Steve Gyles

Yes it was painted! Thats why I am inquiring about having it balanced. Does anyone know what type of buisness that would do this? Maybe a machine shop?
WMR Bill

Bill

I have always been told never to paint a balanced propshaft. Strip the paint off. That's your problem.

Steve
Steve Gyles

If you had a hard time getting the U joint together you may have one of the rollers laying at the bottom of the cap which will move the shaft off center. This isn't hard to do during assembly. The edge of one of the rollers gets caught on something and ends up at the bottom of the cap. You should easily be able to find someone to balance the shaft, just ask at a local dealership, truck repair shop or speed shop as to who the use.
John H

Our drive shaft repair is in Ocala Florida its about an hour away . Any truck stop or truck driver should know where a drive shaft balance /repair shop is . ASk at your local repair shop or parts house or your favorite junk yard .
whipteachr

Wmr,
For reference to have my propshaft (driveline) balanced the cost was about $120.00. That may seem high,however they found one of the yokes was installed somewhat missaligned with the propshaft and had to cut it off and reweld. They also replaced both u-joints, one of which I purchased at their shop included in the $120.00.
I initially took my propshaft in for balancing because I could not find any balancing tab or weight on the shaft and concluded it was knocked off. I also thought the propshaft was put into service over 40 years ago and now modern machinery could do better job of balancing. Plus if it was off the car for any length of time, it may have been knocked around a bit.

Ray
Ray Ammeter

One thing not mentioned yet is that a driveshaft inbalance will be at 4.3 times the frequency of a wheel balance problem. It will mostly be felt through your butt. If you have felt a wheel inbalance before, then the it should not be difficult to "feel" whether your problem is a driveshaft or wheel problem. $120 is very reasonable for the driveshaft rework and balance. I had my work performed at a reputabe truck repair place in Woodstock,Il. I tried contacting a driveshaft repair shop (in farm country) and they would not touch it. Go figure!

Incidentally, the truck repair shop also re-arches springs the old-fashioned way---- anneal- form- and re-temper. Seems this is a normal process for the large commercial trucking arena. They can even build to spec if they have the raw steel stock. That was about 6 years ago. I don't know if they still offer this now.
Chuck Schaefer

This thread was discussed between 27/07/2007 and 01/08/2007

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