2nd gear blocking ring failure BJ7

[bnw]

The new 2nd gear blocking ring completely failed after less than 200 miles of normal driving. There is virtually no gap between the ring and the gear when the slider is nudged into position. What might have happened here?

 

[homebeforedark]

Have you disassembled the gearbox yet? Was second gear replaced at the same time? I have a BJ7 gearbox that looked so good from the top that I almost felt guilty taking it apart until I found that the fourth gear baulk ring was completely worn out. Second and third looked like new since the car had only been driven appx 600 miles. The cone on the first motion shaft was blue from the heat caused by the friction. I did not catch a thrust washer out of place but I will admit that I was not watching that closely since there was no report of a problem by the owner.

I purchased both the stock baulk rings and the heavy duty baulk rings to see if I could tell a difference but it will be at least two weeks before I am ready to see if I can tell a difference.

I have five big Healey engines to rebuild and four more gearboxes to rebuild and three of the combinations go in rotisserie restorations so I don't want any chance of having to remove them once they are in place. Please stay in touch or PM me when you have more info.

Alan T

 

[57_BN4]

I posted about my experience with repro synchro cones here, although this relates more to the manufacturing quality of 3rd/4th rings. Planning to give the rebuilt gearbox another run in a few weeks, hopefully with better results than last time.

Can you identify which type of synchro cones went into the gearbox? The better quality type have fine machining marks running across the outside surface whereas the others have more of a cast/forged look.

Also, is it possible that 2nd gear shift fork is not quite sitting in the right place in neutral so there is always slight pressure to hold the synchro onto its gear? Or maybe too much endfloat is allowing the mainshaft to move rearwards... guessing a bit there. You'd see a lot of brass in the oil if it had worn down from overloading.

Andy.

 

[bnw]

Thanks you guys. We will be tearing it down sometime next week.

 

[Stretch]

After a rebuild I had difficulty shifting between third and fourth gear. Troubleshooting found brass in the oil. Teardown revealed I had a sliding hub that was binding. One of the new synchro rings also quickly became worn. I had not reassembled the concentric sliding gear assembly exactly as it was before. Because of this there was some binding from the wear pattern in the gear teeth. Maybe this experience will help.

 

[homebeforedark]

I'm still interested in the diagnosis. Have you disassembled the gearbox?
Alan