Lotus Elan and Lotus Elan Plus 2 Forums

Before my Elan retired I had a knocking sound when reversing, all forward gear were OK. With the drive train due to be removed soon I would like to sort this out, so what is the most likely cause? I don't intend to strip the gearbox and have always thought that the cause of the sound was the drive shaft UJ's.

Regards,

It could be a chipped/missing tooth on the reverse gear. I had a TR3 that did that and it was a chipped/missing tooth on the cluster.

Where does the knock sound like its coming from?

Hate to say it but a friend had a similar thing happen to him. Turned out it was one of the lugs that had snapped off the diff, it was only driven slowly forward but sounded ok but if you reverse up a hill for example (have some load on the reverse gear) then push the clutch in it would clunk through the drive train quite violently.

I had the same knocking in reverse once when an upper diff mount bolt was loose

cheers
Rohan

Thank you for your replies.

When I remove the gearbox/driveshaft/diff I will see if anything you have suggested is the reason for the knocking. If memory serves me correctly the noise was further back than the gearbox. We shall see.............

Just put my diff back in and discovered a broken ear on the upper right hand diff mount...... this can also cause knocking in reverse.

cheers
Rohan