Mk1 Lotus Cortina strange noises (bear with me....)

[7skypilot]

Does this post refer to Paul and Jan's Lotus Cortina? If it is I know that they have tried just about everything except swopping the gearbox and that they will be very grateful for any response from this knowledgeable forum.

They don't have an Elan, yet, but their wonderful collection does include two Mk14(?) Elites (amongst many other classics) so they are halfway to becoming fully fledged forum members. I'll push them into buying an Elan soon...

And we all share the same love/hate relationship with the TwinCam and it's gearbox.

Welcome, and I hope they resolve this continually frustrating problem

If it isn't their car, I'll suggest that they join the Forum asap so they can (hopefully!) find the solution.

Bonne Chance,

Don

[2cams70]

You should be able to do a reasonable assessment of the gearbox by removing the top cover and inspecting the gears. It's likely that you can lever the laygear forward and backward too to do a rough check of end float.

Thoroughly check the exhaust for rattles though as already mentioned before going too far. It can be a source of all manner of weird noises!

[sdenny]

Does this post refer to Paul and Jan's Lotus Cortina? If it is I know that they have tried just about everything except swopping the gearbox and that they will be very grateful for any response from this knowledgeable forum.

They don't have an Elan, yet, but their wonderful collection does include two Mk14(?) Elites (amongst many other classics) so they are halfway to becoming fully fledged forum members. I'll push them into buying an Elan soon...

And we all share the same love/hate relationship with the TwinCam and it's gearbox.

Welcome, and I hope they resolve this continually frustrating problem

If it isn't their car, I'll suggest that they join the Forum asap so they can (hopefully!) find the solution.

Bonne Chance,

Don

Yes Don, Paul is my brother in law. Time's are getting hard though - he's down to just the one Elite now

He is trying to get another box to try to see if that fixes it. It is, as you say, pretty much the only thing he's tried yet.

I wish you had pushed him in to buying an Elan sooner - it would have saved me a fortune. We were at the NEC in 2016 and he said to me "That Elan needs buying - if you don't, I will" and for some reason I did....

[denicholls2]

I favor the exhaust comment, but "metallic sound on overrun" sounds immediately to me like a loose timing chain. They won't rattle at all when the engine's pulling, but when they're free to flail they start lightening the timing cover.

Very unique "tractor-like" noise, lots of clatter. With the engine idling, put a big screwdriver against the cover and the handle in your ear and blip the throttle.

Would also manifest as a wandering timing mark.

I'd wait to pull out the transmission and take it apart until I had a reason beyond "funny noise." But some enjoy that activity and it isn't spring yet.

[2cams70]

Only happens in top gear so unlikely timing chain related

[sdenny]

Some movement perhaps......

A different pair of driveshafts were used (previously he'd only had one spare, so had swapped out both left and right, but not at the same time) and things are currently looking good.

Examination showed the splines to be worn (i think he said they looked more triangular than square), so perhaps this was the issue. He needs to "properly" put things back together and do some more miles, but he seemed happy when i spoke to him the other day.

Thanks for all the suggestions

[7skypilot]

Good news - I'm pleased the problem has been solved, and I look forward to seeing Paul's excellent Lotus Cortina on our next Rally.

Luckily, on the Elan, there are no 'half-shafts' to rattle on the overrun, just those pesky donuts we all have a love/hate relationship with!

[sdenny]

just those pesky donuts we all have a love/hate relationship with!

Surely you mean hate/hate relationship?

[Melcher Roger]

And now i'm very curious what have been done to solve the rattling problem on overrun ?
I have exacly the same issue on my 66 mk1 Lotus Cortina with 2000E Gearbox and several failings to report .
Changed 2 gearboxes with rebuild at BHG and Throbnozzle , fit new propshaft from Bailey Morris, fiddling with diff angle and drivetrain angle , try out of thicker 85W140 gear oil , changed from pre engaged to inertia starter motor , aaaand so on and on and on . Gearlever sizzling was solved by fabricating a thicker nylon Gearlever half ball on a lathe that fits firmer in the remote Cup . Helix Clutch was done new when the car was rebuild in 2015 , flywheel balanced, starter ring new .

Any Tip is welcome . many Thanks and Greetings from Luxembourg . Roger