Lotus Elan and Lotus Elan Plus 2 Forums

My Sprint had started making some 'clunking' noises from the rear on the RH side? It's as if something in knocking as the engine revs. It especially bad turning right or starting off from stationary. I have had a look under the rear and everything looks ok, even the donuts looks fine? Anybody come across anything similar? Failing that, can anybody recommend a good Elan engineer in West Cambridgeshire??

Carl

Diff tie rods?

Diff top mountings?


John

I agree with John on the diff tie bar bushes and mounts. The propshaft rotates, the diff twists under load, slack bushes and mounts allow the doughnuts to rap against the chassis....nhappened to me a long time ago

john.p.clegg wrote:Diff tie rods?

Diff top mountings?


John

Thanks John,
Strangely, one of the lower diff tie rods was loose, one of the rubber bushes seemed to have come out of the 'hole' at the bottom of the diff. I tightened this but still seem to have a 'issue'. I have not checked the top mounting though... How do you get to them?

Carl

I don't know....on my plus2 it was seats out / or was it empty the boot? and try to get a spannner under the petrol tank whilst at the same time get under the car and get a spanner above the diff....LOTUS ( well not really ).

John

Diff top bolts between the struts in the boot.

Couple of other thoughts from a total non mechanical expert but fairly easy to check:

Propshaft flange bolts tight?

Caliper or disc loose?

Is the wheel properly tightened and engaged on the drive pegs, have any of the pegs rounded holes in the wheel itself and on application of power they are moving?

Clamp the nut (or is it the top of the bolt) in the boot with a mole wrench and rig it so that it cannot rotate. Then from underneat use a socket set with long extension rods to tighten it up.

Or make it a two-man job.

This is weird. I was out for a drive today and all of a sudden I got a clunking noise form the rear of the car. I checked the donuts and couldn't find anything wrong so unwilling to proceed I called roadside assistance. While waiting for the tow truck to arrive I checked my email and found this thread. As I was reading I thought of another simple cause. I checked the spinners on the wheels and found one to be loose. I tightened it up, cancelled roadside assistance and drove home.

donselan wrote:This is weird. I was out for a drive today and all of a sudden I got a clunking noise form the rear of the car. I checked the donuts and couldn't find anything wrong so unwilling to proceed I called roadside assistance. While waiting for the tow truck to arrive I checked my email and found this thread. As I was reading I thought of another simple cause. I checked the spinners on the wheels and found one to be loose. I tightened it up, cancelled roadside assistance and drove home.

I though about that as well, swapped my nice shiny restored spinner for one I could hit with a hammer (!!) but the noise was still there...

Carl

The last time I experienced this it turned out that one of the top mounting lugs on the axle casing had broken through from the bolt hole. When I removed the diff from the car it was plain to see that there was very little material between the bolt hole and the outer part of the lug. I looked at the several spares I had and found that they all differed (sic) slightly so I replaced it with the one that had the most material surrounding the bolt hole and fitted the reinforcing angle piece used on the Sprints and very late S4s. The original casing is still waiting to be welded up - 25 years after the event. I'll get round to it one day when they are scarce enough to make it worth doing

Nigel F.

nigelrbfurness wrote:The last time I experienced this
Nigel F.

In my case it turned out to be a worn out propshaft UJ.

Worth a look.....

A loose rear stub axle will make a noise when pulling away, and when changing from drive to coast in gear. I have had this, and the noise tends to be high pitched like a ticking or creaking noise if the axle is slightly loose in its Morse taper.

If the looseness is greater perhaps the noise goes down in frequency like a clunk?

Note that loose does not neccesarily mean you can feel play. It's easy to check - just take off the rear wheel and undo the sub axle nut and thick washer. Check that the stub axle flat shoulder is below the level of the hub shoulder. If not, the softer hub is worn and the axle cannot be tightened up to it. You could perhaps dremel away a SMALL amount of metal from the washer where it covers the sub axle (10 thou max?) to give you a little extra room for the axle to be pulled into place. Any more than that and I would think that the hub needs to be replaced.

Then refit the washer and nut and tighten it to 100 ft lbs. You should hear the hub ticking into place as the nut is torqued up.

Cheers,

Dave Chapman.

Thanks for all the advice, on the basis that the rubber diff mounts and torque rod rubbers were last changed in the late 1980s I will change these and see what happens.. It about time they were replaced anyway ...

Carl

Thanks for all the advice. It was a missing donut bolt on the 'other' side to the noise causing the problems... Car now has two nice new shiny diff mounts now as well, the old ones were 25 years old but still looked pretty good... Torsion bar bushes look pretty knackered so replacing these as well..

Carl

If you had one donut bolt fail I would replace them all if you have not done so already and make sure the new bolts are torqued correctly

cheers
Rohan