[Healeys] Gearbox Problem

John P. New jnew at hazelden.ca
Fri May 19 17:30:40 MDT 2017


I had this problem about 15 years ago after Rich Chrysler restored my BJ8. The transmission would pop out of 4th gear when, "letting off the accelerator pedal in the middle of an acceleration; letting off the accelerator pedal to engine brake," which is from my notes at the time. After disassembling the gearbox and carefully examining everything, his diagnosis was:

"The cause of the slipping out of 4th is due to two things, each of which might not have caused the situation by itself, but combined to cause problems.
The 3rd/4th speed gear selector fork shows a lot of wear on both sides where it pushes against the shifter hub in both directions. Also, there is wear on the 3rd/4th gear internal synchro hub. This is the sliding assembly preloaded with the 3 sets of springs and balls.
To replace the offending parts will require: 1 selector fork, and 1 3rd/4th synchro hub assembly"

I had some other work done on the gearbox at the same time, which included replacing the layshaft, reverse gear/idler and the 4 caged needle roller assemblies for the laygear.

After all this was done, it never popped out of 4th gear again, no matter how much coasting or engine braking I applied.


On May 19, 2017 03:15:22 PM Bob Spidell wrote:
> My gearbox is popping out of 4th and 4th/OD, usually coasting in gear 
> downhill, but sometimes randomly.  Anyone know what the typical cause(s) 
> of this are?
> My guess?  My rebuilt engine has (much) more compression, and the 
> 'reverse torque' from coasting it causing something to flex or buckle in 
> the box.
> TIA,
> Bob
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