Perhaps anyone here knows more than I'm finding out.
When running the engine on the dyno Frank mentions that a 2800 rpm stall speed torque converter is recommended for the cam that is in this engine, and almost certainly the factory standard would have been 1800 rpm. Of course I'm not building a drag car, so I go to checking. Tucker was unsure of stall speed, but their new Allisons do come with the torque converter, not sure about back in 1989. Weller, the Allison dealer, said the at545 would have come with a torque converter, and Allison doesn't designate by stall speed but rather by percentage of slip. There is/was no lock up torque converter for the at545. They said there are only two torque converters available at this point in time, one for a gas engine, the 275 with 1.96 percent slip ratio, and the 290 with 1.72 ratio for diesels. There have been a couple others over time, pre 1992 the 275 was the 270 as mine is, and a 230 for diesels that was a 2.90 ratio. Higher percentage slip of course would equate to higher stall speed (smoother shifts?). Also seems the the at545 doesn't build up the pressure needed to lock up the internal clutches below about 2200 rpm iirc, which can cause damage.
It seems there is only one choice for the gas engine and that's what I have. It's recommended to replace or rebuild the torque converter when replacing or rebuilding the transmission due to build up or damage caused by shavings ect in the torque converter. My trans pan was very clean and magnetic plug were very clean so we just serviced the trans and putting it back in. I'm thinking the same with the torque converter.
The whole concern with the cam and stall speed of course, is not wanting the engine to die when put into gear at idle rpm because of the overlap of the cam. Even though we didn't try to idle below 850 rpm on the dyno because we couldn't unload the engine while hooked to the dyno, it idled very smoothly at 850 rpm. Guessing because of the stroker build and the efi.
Thoughts, knowledge, anyone? My gut feeling is I'm ok reusing what came out, but I just don't want to have to take it apart twice.
I know Tucker has worked with their local Allison dealer over the years to refine the transmission to Sno-Cat relationship. In a conversation with the Tucker factory, they suggested I call that dealer, Pacific Power Products, and more specifically speak to a fellow named John Edwards. I did call and found him to very knowledgeable, friendly and helpful.
When it comes to Tuckers and Allison transmissions, I think he's probably THE guy to speak with...