Transmission/drive line vibration

[Canada Kev]

Though my car is off the road for the winter, I thought I might hopefully figure out what might be the cause for this vibration.

Basically, I have a brief, consistent and repeatable drive line vibration that occurs right at 1200 rpm when accelerating from a stop. When I say 1200 rpm, it really is over a small range, perhaps 1150-1250 or even less. It doesn't seem to be a clutch issue where it's not completely released, as by that time my foot is usually off the clutch.

Could this be motor or transmission mounts? The motor mounts are recent, but the tranny ones are old.

Again, this happens every single time I'm accelerating away from a stop. The short little vibration happens right at 1200 rpm.

[Oh Haha]

It could be many things obviously but I would try replacing the gearbox mounts and see if it helps.
Where do you feel the vibration? In the shifter or the steering wheel?
Tires/wheels can probably be ruled out in this case.

[Canada Kev]

It's not in the steering wheel. I seriously doubt wheels/tires are the issue - 1200 rpm is barely a walking speed in first and I have changed the rolling stock a few times with the same issue.

Basically it feels like a very brief vibration at a certain narrow range of engine speed, but is quite difficult to pin down the exact source. It's almost a shudder, or the lower frequency vibe that some of those rice wagons get with all the sub bass vibrating their license plate.

When I get the car back on the road in the spring, I'll have to try to hold the car right at that rpm to see if it is easier to locate. It will occur if I lug the engine down to 1200, but it only happens when accelerating back to speed again. It doesn't seem to occur when coming to a stop. I've never tried it in any other gear other than first, either.

[fastfredracing]

Maybe have a look around at your axle shafts, and rear wheel bearings. Could be the axle bolts starting to loosen up, but is sounds as if you have had this problem for a while, and by now the axle would have fallen off. A rear bearing that has loosened up could allowing the spindle to shift around, it sounds as if this shudder happens right when you are starting to put torque to the driveline. And the last think that comes to mind is a long shot, but maybe the parking brakes hanging up slightly, maybe a holdown or return spring has come off, maybe sticky cable not releasing all the way. Good luck, keep us posted

[Joe Bob]

I found a noise like that....I put the car on a set of rollers at a friendly smog shop. They didn't use it a lot because the rolling test was for another County down South. Vacation residents had to register their rides and were too stupid to use the vacation address.