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TR4/4A Help with gearbox dissassembly

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John_Progess

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I am trying to disassemble a TR4 gearbox. This gearbox has no serial number stamped on it. It is a full syncro box with the constant thickness mounting flange. My problem is that I cannot get the counter shaft out of the box. The rear small thrust washer will not separate from the counter shaft. The tab on the washer is lined up with the slot in the case but will not slide out from the counter shaft. It will slide around but not come out. It feels like there is something on the thrust washer that is hung up on the inner bore and will not allow the thrust washer to be slid out from between the case and the counter shaft. When I try to pry the thrust washer out from the counter shaft the entire counter shaft moves and binds in the case. There is some clearance between the thrust washer and the counter shaft. I can insert a thin piece of steel in the clearance but it will not go completely through the clearance, it is hitting something. I am assuming that the small thrust washer must be extracted first then the counter shaft will have enough clearance to get it out of the box. I have had both the large and small thrust washers tabs aligned with the slots in the case but still no luck. Am I missing something? Thanks for your help.

John
 
You've already removed the actual shaft, right? It taps out through the case first, but normally that's before you remove the input and main shafts. As I recall, you should be able to just lift the gear cluster that rides on it out, once everything else is out of the way. But you can also pick out the thrust washer first if you want.

Perhaps one of the needle bearings is caught in the bore? Can you feel anything unusual through the hole where the shaft goes?

Another thought, did you install a dummy shaft to hold the needle bearings in place? If so, it may not be in just the right place and be hanging up on the case. I think that's only needed for the 3 synchro box (with the open needles) but my memory is fuzzy on that point.
 
The rear cluster gear needle bearings did fall out even though I had a dummy shaft installed. It must have been to small a diameter. The front set of bearings seem to be caged and are still in the cluster gear. I have removed the dummy shaft and I think all the loose bearings but the cluster gear still will not come out! I have done this in several tranny's so I could not figure what is holding the thrust washer in place. I will try again today! Thanks for the reply and have a good day!

John
 
It sounds like maybe a ridge is worn into the thrust bearing. Lay a towel on the table, line up the locating tab with the notch in the case and tap the case against the table upside down.

If that doesn't get it, then there is still a needle or some other detritus caught inside the bore. If that's the case, try working on the washer through the shaft bore at the rear.
 
I am wondering now if the front bearing is caged and the rear bearing fell apart, maybe there is part of the cage caught in between the thrust bearing and the cluster gear. The needles that fell out look like they should be in a cage as they have extensions on each end for the cage to hold them. Thanks for your help and have a good day!

John
 
I believe that drawn cup full complement needle bearings were used on the cluster gears of the Tr4 gear boxes, instead of the loose needles used on the earlier 3 synchro boxes.
Berry
 
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