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MG MGB Technical - New Synchro rings are tight??

I just got these from LBC (MOSS) for my 79 4 speed. They are tapered so they can only go one way but they appear to bind on both the second & third speed gear hub. When I measure which is difficult on a taper they look like they are .010" small compared to the used ones.
Do they wear in (I wouldn't think so)? Is this a common problem? Should I send them back?

This is really frustrating.

paul
PRC

synchro rings wear...which is why you replace them. They don't go all the way onto the taper.
D O'Neill

Normal, I agree.
Paul Hanley

PRC,

If they didn't bind you would have a problem - it is the binding that synchronises the gear and hub speeds so you can change gear!
Chris at Octarine Services

I really appreciate the feedback. It just seems like second gear does not spin free, it is very tight to spin after tightening up the locknut on the shaftend. It has to do with the synchro ring being pushed up on the second gear taper land (I hope I am making sense here).
Is this all normal to have the tight 2nd gear?

Also how tight is the shaft end nut suppose to be that holds this ass'y together?

Thanks again guys. You can understand my concern with all the work and time to getting the box out and going thru it and then putting it back in all in hopes that it will work fine.
PRC

The gears should spin free when not engaged. Make sure you have not mixed up any parts between the first/second & third/forth sliding hub assemblies and syncros. Also check that all the thrust washers on the main shaft are in there proper places.
John H

PRC,

As a hobbiest who's built up only a half dozen gearboxes, I'm always concerned about the final product too. Rest assured, that once the torque of the engine is pushing everything around--rather than by your hand, everything will be ok.

Cheers,

Paul
Paul Hanley

John, when you say "not engaged" you are referring to the sliding ring is in the middle position? In this position the second speed gear and third speed gears do not rotate freely. This is because of the taper fit of the baulk rings on the corresponding hubs being tight.
I'm hearing conflicting informatioon as what to do?

Thank you.

paul
PRC

The baulk rings do not go all the way on to the gears, as stated by several above. However, with the gears disengaged - in neutral - the gears should spin freely. If tightening the third motion shaft nut causes them to drag SOMETHING IS WRONG! Aside from defective baulk rings, misplaced/wrong thrustwashers, shafts not located correctly, synchro hubs assembled wrongly are the most likely culprits. With all gears in neutral and everything tight, all baulk rings should be rattly loose; poke them with a wire to be sure of free movement.
I had one instance of a defective ring, on a 3 synch MGA box. It was a Moss part (which I still have somewhere), and I found several other people who had met the problem at the time, but from other suppliers, so somewhere at the source there was a machining problem. Those were too loose/oversized, so they didn't function for long, but you didn't know until you got it all together and drove it for awhile, unless you had a lot of gearbox experience. That was in the days before computers, and Moss did not respond to my handwritten letter of analysis, but they did refund my customer's purchase price, without coverage for labor of course. Since he had had the box rebuilt in Washington state before moving here, he was out double labor.
FRM
FR Millmore

Chris, I just read your article on the gearbox rebuild and it said that there should be 1/8" between the baulk ring and the face of the 2nd or 3rd speed gear. So this tells me that they shouldn't go all the way up the taper and the fit is what makes them perform properly, correct???
Your article did help greatly.

paul
PRC

Paul,

Yes, but the gears should spin freely if the ring is clear of the cone. Does second gear revolve freely if you push the hub over into first gear position?

The end nut should be tight and there should be 5 to 8 thou clearance between the gears and the thrust washers.
Chris at Octarine Services

This thread was discussed between 20/02/2007 and 22/02/2007

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