C4.1 gearbox to chassis screws coming loose
 

Used my C4.1 for the first time last eve and noticed after a couple of heats my gearbox to chassis screws had come loose, all 4. They still do up tight so don't think they are stripped as such. Has anyone else suffered from this?

Any remedies?

Don't think longer screws are an option as would touch the diff? Maybe threadlock might help even with delrin casing?

can't say I've ever had that issue myself or heard of anyone else having a problem.
Pop a drop of threadloc on them before doing them up and they shouldn't come loose again.

Cheers G

Use a similar length metric screw as they are a bit fatter

Cheers Dan, will try the threadloc first as would imagine going metric will mess with the existing thread slightly meaning no going back ;-)

Threadlock is for metal to metal screws, not into delrin/plastics. Doing this will most likely make the problem worse.

I'd try a longer 4-40 screw.

Thread lock is for both metal to metal and metal to plastic applications. Setting when starved of air.

I need to open it up to see, but not sure there is much screw clearance to the diff on the c4.1 case to use longer screws? That was my first thought. Will check though.

Happened to me. Threadlock cured the problem. Dismantled the casing several times since and threads fine. So threadlock on delrin is ok.

Longer screws will hit the diff gear, so options are threadlock, metric screws, tiny blob of superglue on the thread as a last resort.

Some threadlock compounds react with plastics, softening the plastic threads and ultimately stripping them out.

Neal is right by the looks of it, some threadlocks aren't advised for some plastics, but there are some versions for plastic (loctite 425) apparently. Tiny amount of CA looks fairly popular too.

Buy a helicoil kit (4-40, M3) and pop in a Helicoil: you'll have a metal thread to work with. If you then even need threadlock in the first place it will stick, and the thread will hold up much better :) Also, you can use the helicoils elsewhere on the car if you strip a thread - why chuck away an (otherwise) perfectly functional part?

I've got a load of Centro C4.1 bits in the for sale section new including a spare gearbox housing if you're interested? No stripped threads.

Thanks Hog, will bear in mind if the lock method doesn't hold up.