Uncle chrispalmer,

A 1975 164e in Montana?

Agreed with Uncle walrus3. An M410 in good shape with all the works (driveshaft, transmission support cross member and bushing, other pieces from donor car) for the swap from BW35

The Borg-Warner model 35 (BW35) on 140/160 is an inefficient and heavy beastie.

Your Volvo 164e driving experience will wake up with a Borg and Beck M410 transmission behind the lovely Volvo B30 F engine. Your mileage greatly increases and your 164e becomes a real road warrior. You'll love the torque through the gears!

Follow you Volvo green OEM or Haynes service manuals for VOlvo 164 and the Volvo 164 owner manual to check fluid levels and perform other procedures.

Your post suggests you've not yet diagnosed your transmission for problems:
- Fluid level: Two low? Don't overfill the BW35 transmission (barely overfill is alright if recurring leak at known rate - current lubes don't foam up as badly).
- Fluid level: Too high? Unlikely.
- Fluid quality: I'm uncertain the proper fluid type for the BW35. I think automatic transmission fluid "Type F". The fluid should be bright rosy red color, clean, and not smell burnt like hot brake or burning printed circuit board (like burning phenolic). If fluid is dark red or darker, fluid must be replaced.
- Fluid quality: If fluid is brown and foamy, the in-radiator transmission fluid cooler (if equipped on your 164) is exchanging fluid with the engine coolant. Your may need to replace the engine coolant, repair/replace the radiator, inspect and, if needed, replace the transmission fluid or repair/replace the transmission. Engine coolant mixing with transmission fluid will see an immediate deterioration of the automatic transmission.

If the fluid is not clean, clear, and smells burnt, perform a transmission fluid flush (your or a oil change place). If the drained oil in the transmission contains some particulates or a pile of dark granular goop (usually the fluid is black also), that is clutch disk matter from the transmission. Your transmission will require rebuild or replacement depending on the severity.

Questions and comments?

Hope that helps.

Buttermilk.