A NEW PROPSHAFT
Next, attention turned to the vibration that we had noted on our initial drive home after buying the car. This came in at 40mph, though it did seem possible to drive through it to a certain degree as it appeared to lessen after around 60mph. I do hate driving a car with a vibration though, not necessarily because it makes the car less comfortable, but more because it is an indication that something is wrong, and that something could have serious consequences – when you combine the weight of a car and its components with the speed at which certain things are turning, then you will quickly appreciate that there are considerable forces at work which may be acting upon some large chunks of metal. The idea of something like that being weakened and finally calling it a day at 70mph is not a pleasant one.
This particular vibration could be felt through the seat rather than through the steering wheel, which suggested that it was not related to the front wheels or the steering. The tyres on the car when I got it were time expired, so I had a new set fitted and the wheels balanced. The problem remained after that, which did rather discount the most obvious first suspect of an out- of-balance wheel. Just to be sure, I swapped the wheels from front to back to see if that moved the vibration from the seat to the steering wheel, but there was no change, so they were in the clear.
The next item on my hit list of potential problems was a worn or dry universal joint on the propshaft, but checking in the workshop manual and on my car revealed a propshaft with a CV joint at either end, and that there was no provision for lubricating these during service. I did get under the car and try twisting the drivetrain either side of each joint, but could not feel any slack. However, talking to a friend and TR7 fanatic, he suggested that on a car which has been sitting for many years with the joint in one position, the grease can harden or rust can form internally, leading to this kind of vibration issue.
He also suggested that rather than replace the joints, it would be far easier and not cost much more to buy a new replacement propshaft from Robsport which came with everything on it and was ready to fit. I duly ordered one and fitted it, but again it made no difference. That made it a bit of an expensive way (£178.68 delivered) to rule out the propshaft as the source of my problem, but ultimately I was more than happy to have new and freshly greased joints on the car so it was not a big issue.
The vibration, however, remained. So next I drove gingerly down to Robsport in Shepreth near Royston, and their technician Ben took it out for a test drive. In view of the parts that had already been changed, he was confident that the problem lay within the rear axle. This could have been something as simple as a failing wheel bearing, or it could be down to a bent halfshaft or problems within the differential itself. I felt that stripping and rebuilding a rear axle was getting a bit beyond my pay grade, but Robsport boss Simon Hebditch kindly offered to give me a secondhand axle so that I could test it by substitution. Since there was no way of carrying this booty home in the TR7, I accepted gratefully and arranged to return the following week in a more suitable vehicle to collect it.