51 JD A 4th and 6th gear issue

brianxx · Apr 20, 2012

51 JD A, gas. I had a grinding noise when I try to move the tractor. It comes and goes but I finally narrowed down to 4th and 6th sliding and pinion gear. Took 4/6 cover off and found gears rounded off and shiny on one side. When you shift into 4th or 6th the gears mesh and are fully aligned. Main question, When you shift into anything else the slider gear moves outward, should it move out far enough to completely clear the pinion, (lower), gear or remain "slightly" engaged? If they should be free of each other, how? Detents are good, shifting fork lock bolt is good and saftied, very slight end play on counter shaft. I can manually pull sliding shaft further out past the detent to clear the pinion but that means it"s out of the detent. Pinion gear is tightened as far onto shaft as possible. Any thoughts on gear position/alignment?

Rich Duane · Apr 20, 2012

Brian,
When you shift to neutral or any other gear the 4th and 6th pinions should not touch.
To correct this situation you will have to readjust all three shift rails so the shift gates all align when in neutral. It is not a real hard job but you have to disassemble the clutch and pulley remove the right brake assembly, remove the first reduction cover and the shifter cover to get at the shift rails.
The best service manual to do this is for the model 60 as ti has the same transmission setup. The IT manual for the A B G also will work if you have been in one of the transmissions before.
It's quite a bit of taking apart and you will probably need a few gaskets but that's about all.

Rich

brianxx · Apr 20, 2012

Thanks Rich. I was hoping that pulling the right side apart wouldn't be the answer.

Pappy · Apr 20, 2012

Not trying to be a know it all, but you do not have to pull anything off of the right side of the tractor. The shift rail adjustment is under the cover you have already removed that covers the gears. Look at it-you can see the ends of the shift rails at the top of this opening. You will have to remove the gear shift quadrant and then adjust the shift rails. You need a book to explain how to adjust the rails with the screws in the ends of them. Just trying to save you a lot of work. I just completed rebuilding my "52 A and it is not difficult. The 4/6 detent etc is mounted in the left side of the trans. case.

brianxx · Apr 20, 2012

Thanks Pappy. I was going to pull the quadrant off first and hope I could find a solution before removing the right side....again.

Pappy · Apr 20, 2012

One more point---your 4/6 shifter is not adjustable. Before you tear it apart, slide your 4/6 shifter to where the detent pops into place and then examine your gear position. It could be that the part that moves the gear in and out could be bent, or loose on the shaft. Check the easy things first.

51 JD A 4th and 6th gear issue

brianxx

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Rich Duane

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Pappy

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