Triumph Repair: vibration on a 1500 spit (77), shaft bearing, tail shaft

Question
Hi Howard,
I am getting a vibration when the transmission is in gear on my spitfire. It does not vibrate out of gear at all. I put it in gear , with the clutch in as well as out,when its in gear, It vibrates at 2500 rpm or so. I rev to 2500 or so, it is barely there in 1st gear and gets worse as you go up the gears to 4th. I have disconnected the drive shaft and jacked it up, so I know it is not the shaft. motor mounts look old and original, and the trans mounts are saggy and cracked, any chance it could just be the motor/trans mounts, or what else should I be looking at. seems to have just started, not gotten worse over time.
Thanks so much for your help.
Chris Runnels

Answer
Hi Chris,

I take it you mean it vibrates with the clutch in or out when you are on the road and moving because if you are sitting still with it in gear and the clutch in, NO gear in the transmission is turning in that condition.

Do you mean that it vibrates when going fast if the clutch is in or out? And you say it vibrates in 4th gear with the drive shaft disconnected from the transmission?

If all this is true you have a bad bearing either on the tail shaft housing or the rear main shaft bearing is bad.

Howard