B52 gear box problem

[JDFS79]

Thanks a lot i will try to solve this next week when the bushes arrive. I let you know how it went, many thanks again.

[Andy51]

Hi, I believe the best way of finishing the main gear bushes is to bore them on a lathe - set the gear up in a 4-jaw chuck, using the smooth surface on the inside of the recess for the sliding gear at the input end of the main gear to centralise (that's how I did it), then bore with a sharp single-point tool - it should only need a couple of thou' taken out - running clearance on the shaft should be around 1 1/2 thou. If you don't have a lathe, most machine shops should be able to do the job. Andy

[JDFS79]

Thanks Andy i will do it on a lathe at work there is one good for the job.

[JDFS79]

IMG_20160708_181755.jpg

here is a foto where i can see that i have only one bush , i take this foto when i changed the main bearing...

[JDFS79]

IMG_20160708_181902.jpg

,

there is some work done on the inside of the bush, maybe for oil lube.???

[Andy51]

Hi, you should have 2 bushes, pressed level with the outer faces of the aperture - as in your picture. The inside surface of the bushes should be smooth with the exception of an spiral oil scroll cut in, as seen in your 2nd image. The 1st image seems to show a rough surface. I cannot see if this is an old, worn bush or it may be the image quality. You will not remove enough metal when boring to remove the oil scroll. However, it is possible that modern pattern bushes do not have the oil scroll, I replaced mine about 10 years ago and can't remember if the club's replacement bushes had a scroll. Andy

[JDFS79]

Thanks Andy, the 1st and 2nd fotos shows the old bush ,that is currently assembled , do you think the problem is here? Could this bushes make the 4th gear jump under load?

[Andy51]

I am not aware that worn bushes make the 'box jump out of 4th, only the plunger under the gear change drum. Perhaps someone more knowledgeable can help? Andy

[ajscomboman]

I am not aware that worn bushes make the 'box jump out of 4th, only the plunger under the gear change drum. Perhaps someone more knowledgeable can help? Andy

You are correct, worn bushes will have no effect on jumping out of gear. Unless severely worn the selector dogs on a Burman won't cause trouble either. Normally the issues with gear selection are related to worn plunger or gear selector tumbler and also wear on the tumbler guide pins, they normally wear flats on the round pin and then that causes poor selection and false neutrals.