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MG MG Y Type - 'popping' out of third gear.

I have the transmission out of the YT while sorting rear seal leak. (leaked all over clutch) and I want to sort out , if I can, the third gear issue. I read that this is a problem.

After inspection the 3-4 shifter fork is well worn, which I assume adds to the problem, a fork in better condition is going to be installed. I have read somewhere of a "fix" to allowing a bit more travet to the striking dog, by removing some metal off the limit that is part of the shifter case.

I cannot find this reference, can anyone provide the details of this? I am thinking .030 " might do the trick.

... CR
CR Tyrell

This happens on my TC, same box and engine, always has. I just put my knee against the gear lever on overrun in third but this is difficult in a Y. I have never heard of the "fix" you mention but believe it is caused by too much end float on the layshaft. A bit of shimming should therfore fix it but I am unsure how much or at which end. Perhaps others can answer?

Ian Thomson
ian thomson

Normally, popping out of gear is due to the detent springs in the hubs being weak.
Chris at Octarine Services

I agree with Chris - worn springs.
Paul Barrow

Chris, what hubs are you referring to? I can see how the detent springs in the selectors can cause jumping out of gear, and they are certainly first things to check as they are the easiest to access, but there are no "hubs" involved there. I assume, therefore, that you are referring to the synchro. hubs. To check these requires a full strip down of the box, at which time a check on the layshaft endfloat should be done also. I speak from personal experience as having stripped and "restored" the box to address this very problem I replaced everything obvious, including the synchro. and detent balls and springs. Unfortunately I was unaware of the layshaft problem, and its involvement specifically with third gear, at the time and ended up with the same problem after as before. From talking to other people I believe that this problem, if not common, is far from unknown on this box. I hope for CR's sake that it is down to the selectors as reassembling the synchro cones is not a job for the fainthearted.

Ian Thomson
ian thomson

Yes - the three balls & springs in each synchro hub.

Always take hubs apart inside a big plastic bag to catch flying bits - reassembly is easy, use a little grease to stick the balls onto the springs once they are in their holes and use a suitable sized hose clamp to compress the balls level with the hub teeth, then push the hub outer into place quickly to displace the hose clamp and trap the balls.
Chris at Octarine Services

I think i tracked down the Service bulletin number, but I cannot find it in my volume of stuff. It is MG Service Bulletin #71 in regard to the Y-type gearbox. I am just going from memory of what is in it.

I can seee how week springs in the sliding hub could be an issue, but the fork is not throwing the striking dog far enough to engage the balls into the striking dog's detent groove. ( my thought only ). Everything works fine when the shifter is removed. When shifter is in place you can hear the end of the 3-4 shifter rod hit the inside of the housing.

Still working on it,
... CR
CR Tyrell

The selector fork is designed to engage the sliding hub not to hold it in place . Springs in the hub do this job. If the small teeth on third are very damaged this can cause the problem .Worn teeth inside the hub will have the same effect .End float in the mainshaft that carries third gear causes the gear to pull out on overrun due to the angle cut of the gears
Bob Wood

Bob, thankyou for your explanation. You are very correct. I have dropped off the transmission to be examined and fixed. I still want to find the information of Service Bulletin #71 which is regards to the gearbox. Its driving me crazy! Not really, but you know what I mean.

,,, CR
CR Tyrell

UPDATE... As Bob Wood suspected there is too much end float in the mainshaft. .120 in fact. The 3-4th selector fork is very worn as well adding to the problem. Other than that I am glad to say that the gearbox will live to see another day.

.. CR
CR Tyrell

Good to hear that she will live again. Bob Wood .
Bob Wood

Transmission is fixed!! Everything is installed, and put back. Took it out for a test drive and clutch will not fully release, so adjustment made.... better but not much. Other than that, shifts well with no slippage. I do hope the new wetdh plug at the end of the cam stays in this time. Finally got to drive the car with out slipping clutch.

What an enjoyable ride !!!

.. CR
CR Tyrell

This thread was discussed between 04/07/2020 and 24/08/2020

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