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My RAV 4 is producing thumping sounds

Dear Neto,

I have a 1998 Toyota Rav4 with a 3S engine. My  problem is that I hear a low but significant thumping sound somewhere in the transmission whenever I start driving. In vain have I had the car checked by different mechanics.

This problem began when I hit a huge pothole. All the engine mountings and suspension joints and bushes which I thought were the cause the problem are new. What could be causing the thumping?

Okoth.

Dear Okoth,

This is a tough question because you say all your engine mounts and bushings are new. I have a feeling it could be a bad inboard CV joint.

The driveshafts use a special plunge joint known as a tripod joint at the inboard end of the axles. It allows change in length of the shaft as the suspension travels up and down or when the wheels are turned.

It comprises a three pointed yoke with barrel shaped bearings fixed on the ends.

This assembly fits into a cup with three groves attached to the differential. When the bearings fail and collapse, there is space for play and knocking of parts thus the thumping sound when the driveshaft starts turning.

Ask your mechanic to check the inner CV joints for worn out bearings. I hope this will help in fixing the problem.