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MG MGA - Output Shaft Bearing Binding

I have already bugged Barney enough this weekend so I'm going to post this question here.
Rebuilding the tranny and replaced the 2nd gear synchro. Upon reassembly of the gears on the mainshaft, the fit for the final washer (the one that turns and locks everything on the shaft) was a very snug fit. I took everything apart and measured the new synchro ring and it was about .010 thicker than the old so I took a little of the surface off. Things went back together fine, the first gear assembly lightly touched the mainshaft bearing housing but spun freely.
Upon putting the mainshaft into the housing pat way, the shaft starts binding up and won't turn. The front of the mainshaft is in the input shaft and the input shaft turns freely.
Any suggestions?
Steven B

Hi Steven. Did you replace the needle bearings that fit inside the input shaft? If you replaced them and the mainshaft now seems to be binding, I would be wondering if the needle bearings were slightly oversize. Is it possible that a needle bearing has slipped out of place, and is preventing the mainshaft from seating and spinning freely? Just a couple of ideas. Let us know what you find. Cheers, Glenn

Thanks Glenn, I did replace the needle bearings but the input shaft spins fine. It should be stuck too if a needle had fallen in. What a puzzle.
Steven B

If the rear housing is not yet installed the center main bearing my be out of place allowing misposition and interference between the 1-2 fixed hub and the bearing carrier ring.

For the 1500 types a jam nut secures parts on the back of the mainshaft. For the 1600 type a long tube spacer, the rear yoke, and the big nut on the back end secure the parts on the mainshaft. The mainshaft and/or a few parts on the back end may be misaligned until you install the rear housing, the rear flange, and the flange securing washer and nut.

So questions: Is the rear end fully assembled, and is it a 1500 or 1600 type gearbox?
Barney Gaylord

It's the 1500. (By the way, I got the tail bushing loose and will get it out tonight, thanks to your help!)

I have not put the mainshaft bearing carrier all the way into the tranny body. I was checking alignment of the pin in the tranny body to make sure it lined up with the bearing carrier when I noticed the binding in the mainshaft. If thre was somthing wrong I didn't want to have to punch the carrier ring and shaft back out. So, no, it is not all the way in the tranny body yet and tail assembly is not on yet.

Steven B

If you install the 3-4 sliding hub backward it interfers with 3rd gear, you come up about 1/8 inch short of having enough space to get the front and center ball bearings installed at the same time. See here:
Barney Gaylord

One last question. As mentioned above, I milled about .005 off the front surface of the new 2nd gear synchro ring (the face to which the doghouses point.) Will this cause a problem? It seems the real wear comes on the doghouses, not the flat surface.
Steven B

No problem. In operation the only surfaces that touch anything are the doghouse and the inner cone.
Barney Gaylord

This thread was discussed between 06/05/2007 and 09/05/2007

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