I have a 12V Cummins with a fuller 5 speed manual that I am swapping to an Allison 542. I have the Flywheel housing and SAE 3 to 2 adapter ring. I'm looking for the flexplate and spacer and ring to attach the torque converter to the motor.
A bit out of my league here but trying to clarify the setup. If I understand correctly, you have an SAE2 adapter plate on the engine and are using an SAE2 to SAE3 adapter to mount the transmission which is SAE3. That would mean you need SAE2 flex plate assembly. Flex plates for that specific transmission are normally SAE3. Might need to contact an Allison dealer and have them tell you the part numbers you need. Sometimes easier to find things by part number than description.
Correct, the trans is SAE3 and flywheel housing is SAE2. I think I found the part #s for the spacer 3906806 so I've been searching for that one this morning. It looks like the flexplate mounts to the crank via the bolts through the spacer, is there a ring that then connects the flexplate to the torque converter? Was hoping someone here had swapped out their 542/545 and had the parts laying around.
Those transmissions aren't very desirable for swaps due to the lack of torque converter lock up or an OD gear. Have seen piles of them in scrap yards so you're right there should be some connecting parts around. Only thing is most of those would be SAE3 since that is the adapter plate that was normally used and you need an SAE2 flex plate. You might luck up an find a set of SAE3 parts and just change your adapter to that type instead of a mix of SAE2 and SAE3.