MG Car Repair: Transmission vibration, oil leaks, universal joints

Question
I have a 1977MGB which I have contacted you in the past. Thank you for your help. I have a new problen which started  shortly after I had a new clutch installed. A friend of mine did the job, and he has been a mechanic for about 25 years. Everything seems to run fine, and shift fine. I do get a loud vibration sound under the floor around the transmission. While the engine is pulling, everything is quiet and is good. When I let off my foot off the gas to let it free wheel ( no pull )in gear, I get a vibrating noise under the floor that sounds like the trasmission is vibrating on the bottom of the body. If I take my foot all the way off and let the trans pull to slow the car,it stops.I can't get under enough to see if anything on the top of the trans is touching.I do have a slight drip of oil from the trans somewhere and can't narrow down the leak. Possiblly top shifter, or rear seal. That leak is minimal.  Ho[pe this is enough info to narrow down the problem. Thanks

Answer
Hi Robert,

A vibration can be transmitted anywhere in the drive train so you may have to have your friend look at several items. Check the rear transmission mounts to see that they are not broken and check the drive shaft universal joints. Another common vibration can come from the exhaust pipe mounts. Especially if it just started after a clutch was installed.

A clutch and/or pressure plate can cause a vibration but it will be RPM related and can't be altered by acceleration or deceleration.

The best way to find a oil leak is to spray wash the transmission and then run the car at low speeds so oil is not blown all over the transmission and then inspect the oil leak to see where it is coming from.

If you don't have access to a lift just wait until you are ready for an oil change and ask the tech to let you look for a transmission leak while it is up on his lift.

I don't want to alarm you but if you stop all oil leaks on a British car you need to sell it to a museum as I have never seen one.

Howard