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bailee2
09-25-2006, 05:14 PM
1971 TR6, "A" type overdrive, bone stock. Car will vibrate excessively at 60-70mph but will somooth out when the overdrive is engaged. New front suspension, new tires, steel wheels balanced, "U" joints on drive and half shafts tight, new donut bushings on rear end, not sure what may be causing the vibration. Has very slight vibration through 30-60 but really annoying at higher speeds until the overdrive is engaged. Opinons? /ubbthreads/images/graemlins/confused.gif

Brosky
09-25-2006, 06:55 PM
How are the engine and transmission mounts? Any cracks if you push against them with a pry bar?

TR6oldtimer
09-25-2006, 06:59 PM
Vibration when not in O/D, then gone when O/D kicks in, me thinks you have an overdrive problem brewing. I'ld check it out before it goes completely.

Bruno_69z28
09-25-2006, 10:00 PM
Could be a damaged clutch disk (goes out of balance if part of the disk comes apart) or a bad pilot bearing.

Bill

trrdster2000
09-26-2006, 04:53 AM
Where to start with this one? IMHO the rear bearing in your tranny case is gone bad and when you switch to OD the load changes to the rear bearing. Does the transmission sing when you are getting the vibs? I once had a simular problem and 180 degrees the drive shaft and it took most of it away, so I ended up having the driveshaft balanced and it was cured, but yours sounds alot more serious. Wayne

bailee2
09-26-2006, 08:53 AM
Thanks all!
I will look at each area tonight. The transmission would have to come out regardless if its the mounts, clutch or bearing. Not great news but gets me on the right track. Thanks everyone.

bailee2
09-28-2006, 05:55 PM
Thanks all! Looks like the transmission mount was sheared from the moun plate and when load was placed on the transmission it would put the drive train in a out of alignment codition which caused the vibration.
Problem solved.
/ubbthreads/images/graemlins/cheers.gif

Brosky
09-28-2006, 10:40 PM
Glad to hear it was that simple. Over the years, I've found more problems in cars with vibrations from cracked or worn mounts than anything, which is why I suggested those first.

If you don't pry from every angle you can miss a problem with a mount that has weight bearing on it from different directions.

LastDeadLast
09-29-2006, 07:13 AM
Interesting.. I've been having a strange vibration problem too, along with the occasional clutch shudder when I pulled out. I was dreading figuring this one out.

But last night I got the old girl on stands and poked around, it turned out to be a loose trans mount, just like you. Drive train is solid as rock now.. not a very hard rock mind you like granite but more like slate.

Brosky
09-29-2006, 08:01 AM
When I worked for Cadillac in the glorious 80's, I saw a car that had two engines and one transmission replaced due to two cracks that appeared to be minuscule, but under just the right load, engine torque and rpm, sent a vibration through the car that was unbelievable.

I got lucky because of a problem on an Olds 442 back in the 60's where I watched engineers from Lansing disassemble a car that had about 100 hours of labor in it for a vibration, only to find a hairline crack in the transmission mount that wasn't visible to the naked eye. They found it by removing the mount and placing it in a vise, then twisting it from every angle, while looking at it with magnifying glasses on to find the crack.