Triumph Repair: rumbling in car after 45mph, shaft bearings, pinion bearings

Question
I recently bought a 1968 spit fire It runs great in all gears  except 4th rumbles unless your going up a hill than it doesn't rumble and runs fine. What should I be looking at . where the problem could be coming from??? Thank you Judy WI.

Answer
Hi Judy,
A "rumble in the car" narrows the problem to only 1000 possible causes. You will need to get it a little closer to find the problem. The best way is to have the car put on a lift and run the car at the speed at which it makes the most noise while someone is under the car trying to pinpoint a smaller area where the noise is coming from. While it is on the lift you can check for excess free play in the driveshaft universal joints and the rear axle joints and wheel bearings. Also check the rear tail shaft bearings in the transmission and the differential pinion bearings for free play.
That is the standard method to locate a drive train noise.
Howard