BTW, thanks for letting us transfer that 790 chopper last month.
A Torque Amplifier is a headache if you tear into it without instructions or experience. I expected no counter-shaft, and I expected a switch-pitch torque converter. I found neither, and spent many hours getting it disassembled just enough to reassemble correctly. Now I'm waiting on new thrust washers, or maybe you call them thrust bushings, for the counter-shaft. This is what I get for sliding out what I thought was a lower rear combination drain plug and cooled lube return. No way to reassemble except counter-shaft first. It can't just go back in otherwise. All this for a leaking front seal that can't be seen without a lot of dis-assembly. Really an in-case O-ring for the front end of the counter-shaft.
This is a 2-speed transmission, plain and simple.
Edit: 1965 Oliver diesel
Folks, Thanks for all the replies. My TA doesn't do anything when I move it. I will try it when the tractor is under a load and see if anything happens. The old diesel has one weak cylinder and it smokes a lot. Blue smoke. A real mosquito fogger. But it starts very easy I hate to disturb it. You can't find a quart of oil for less than $3 these days so one of these days I will get tired of throwing oil into it and tear it down. Would look into the TA at that time.
The TA will shift anytime the lever is moved if it is working properly. I drove tractors (Ford 9000, AC D17 and 190XT, IH 706,806,,1066, 1256, MM G1000, U 676) with the TA or whatever each different brand called them all my farming life and we never had one damaged. The main use we got from them was turning at the row ends where you could cut your speed in half without throttling back, then hit it back in high after the turn. Of course we also used it when hitting tough spots and needed more power to get thru. Downshifting shouldnt hurt one as that was what they were made for and the tractors we had shifted up and down hundreds of times per day when plowing or discing. Every tractor I ever drove also had braking when downshifting. Many of those tractors had 10,000 hours or more on them also without TA failure.
Now that I have this one back together, I have a few more insights. The input starts with a gear on a one-way sprag. The sprag is on the counter-shaft, IIRC. This should prevent engine-braking in one range. Not sure which, and don't much care. Behind that gear on the main shaft is a wet clutch pack, and it's locked by the application of pressurized hydraulic oil. The shifter switches the routing of the oil. The countershaft is always engine-driven by the sprag, and it drives the pump. But it also always drives a rear gear, which is splined onto the output. This seems to defeat the sprag, or the purpose of it, entirely.
However we will be happy if we can just have 1:1, since we tried a few ways to eliminate the entire assembly with no success. Seems I managed 1:1 through it, and if so then we're happy. Today I begin putting it back into the tractor. In this case, start by attaching the bellhousing, then bolt it to the engine, then put it back in the frame, then lastly re-install the PTO shaft through everything.
Seems that if you were going faster than engine speed, in whichever range the sprag comes into play, the pump would spin faster than the engine speed.
I'll post again after I drive it, to report how it behaves.
What model are you working on ??