2 replies to this topic

[Shredder_DT]

Hey everyone,

I rebuilt my gearbox about 5 years ago. Recently it has started to crunch whilst shifting from 3rd to 4th gear. Shifting downwards isn't a problem.

If I shift slowly and keep the revs up I can get it to engage smoothly.

Has anyone else experienced this before or may know a solution for the problem?

Worst case I'm guessing it'll be a new 3/4 synchro the next time the engine is out.

TIA -Mark

[Spider]

Hi Mark and welcome to the forum.

There can be a number of causes for this on top gear;-

 

     Worn Baulk Ring,

     Split Baulk Ring,
     Using a previously worn Baulk Ring that's been ground in an attempt to re-cycle it,

     The Molly coating on the Gear's cone being chipped / flaked (and this is what it likely is),

     Worn First Motion Shaft Bearing

 

Regardless, we can sit around and offer up suggestions, all we like, but in the end, the engine needs to come out and the gearbox stripped down. Given you can shift OK from 4th > 3rd, I doubt the Sychnro-hub is worn, but of course, once it's in bits, check everything.

[Shredder_DT]

Cheers Spider for input and thoughts. Always hoping for a magical solution but I agree engine out is inedible.

I'll post back in a few months with the findings. At rebuild time I used all new bearings and baulk rings and tried my best at the time to source the highest quality. It'll be interesting to see what has failed.

Cheers!

Edited by Shredder_DT, 17 May 2026 - 03:00 AM.