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TR4 overdrive built from two other boxes - up-date
For those of you that were following my gear box troubles that started with the gear box in my TR4 going belly up as the lay shaft wore and needle bearings fell to bits, here is an update.
I was able to take the overdrive unit and the internal gears and shafts out of an early TR3 gear box. My goal was to take these parts and mate them to a late TR3 gear box case so that I could use it in my TR4. All of the gear boxes were on hand and I (foolishly) thought it would be just a lot of work. It turned into more.
The overdrive unit ended up being non functional and missing the eccentric cam. But thanks to the help from members of this forum I was able to get enough information to trouble shoot the overdrive and get it working. What was wrong with it was the eccentric missing, the pump was sticking and the oil passage from the pump to the operating valve was blocked. Once all that was fixed, I was able to bench test the overdrive off the gearbox to confrim it functioned. I did have to manufacture a puller for the pump but that was simple enough.
Turning to the gearbox, all the gears went in fairly well. Again I had to manufacture a temporary lay shaft (I used wood) to hold the needle bearings in place. Tips here for those who want to rebuild a gear box 1) make the wood layshaft 6-3/8 inch long, 2) remember to invert the gear box when it is time to reinsert the real layshaft, 3) make sure you have the synchro cups ligned up correctly or the gear box will lock up. I also fabricated a tool to drive the rear main bearing home out of 1-1/2" pipe.
All that is left for me to do is get a helper to put the finished transmission in the TR4 and them make sure I can keep the Stebro exhaust out of the way of the overdrive drain. Oh and find an overdrive switch for the steering column, a right angle drive for the speedo and a gearbox top switch (if you have some for sale let me know).
I will update my web site with pictures I took all along the way, so take a look there for all the details.
All in all I would say it was worth it, even if it took longer then I thought. If you are tempted to tear down your gear box, I would say go ahead and do it. Just make sure you have a good clean spot to lay out the parts.
For those of you that were following my gear box troubles that started with the gear box in my TR4 going belly up as the lay shaft wore and needle bearings fell to bits, here is an update.
I was able to take the overdrive unit and the internal gears and shafts out of an early TR3 gear box. My goal was to take these parts and mate them to a late TR3 gear box case so that I could use it in my TR4. All of the gear boxes were on hand and I (foolishly) thought it would be just a lot of work. It turned into more.
The overdrive unit ended up being non functional and missing the eccentric cam. But thanks to the help from members of this forum I was able to get enough information to trouble shoot the overdrive and get it working. What was wrong with it was the eccentric missing, the pump was sticking and the oil passage from the pump to the operating valve was blocked. Once all that was fixed, I was able to bench test the overdrive off the gearbox to confrim it functioned. I did have to manufacture a puller for the pump but that was simple enough.
Turning to the gearbox, all the gears went in fairly well. Again I had to manufacture a temporary lay shaft (I used wood) to hold the needle bearings in place. Tips here for those who want to rebuild a gear box 1) make the wood layshaft 6-3/8 inch long, 2) remember to invert the gear box when it is time to reinsert the real layshaft, 3) make sure you have the synchro cups ligned up correctly or the gear box will lock up. I also fabricated a tool to drive the rear main bearing home out of 1-1/2" pipe.
All that is left for me to do is get a helper to put the finished transmission in the TR4 and them make sure I can keep the Stebro exhaust out of the way of the overdrive drain. Oh and find an overdrive switch for the steering column, a right angle drive for the speedo and a gearbox top switch (if you have some for sale let me know).
I will update my web site with pictures I took all along the way, so take a look there for all the details.
All in all I would say it was worth it, even if it took longer then I thought. If you are tempted to tear down your gear box, I would say go ahead and do it. Just make sure you have a good clean spot to lay out the parts.