Hey all,
I was thinking about doing this sometime in the next year, so I thought I'd better get a little insight into this. I'm pretty new to wrenching on volvos (Very new), previously most of my experience comes from working on my old early 70s plymouth fury (I know, pretty big difference).

Anyhow, I noticed that my 79 works pretty hard to cruise at around 70mph, Could just be a lack of insulation not muffling the engine sound, I don't actually know what RPMs it's running at that speed but It's not really fun at all to drive on the interstate.

I chalked this up to it having the old 3 speed automatic, So I was thinking it might be a good idea to swap in a newer 240s 4 speed auto, I haven't seen anyone talking about doing this but I figured that the car has the same wheelbase as later models, same engine block, it shouldn't really be that hard?

I was wondering if anyone had done this, if it would be possible, and what he pitfalls of doing this might be?

 

you'll need the driveshaft from the newer 240 too, as the overall length is different.

For the AW7x family of transmissions (used on all 240's from the mid 80s on), you'll need to wire up the OD solenoid, and add a OD solenoid relay and switch.

 

Thanks Pierce, I've read a little bit about bypassing the electric OD on this forum, would it be basically the same principal?

I had an idea that maybe the driveshaft would need to be swapped out too, any compatibility issues there? Like would the differential need to be swapped too? Is any year 4 speed auto better to look for or are they all basically the same?

Lastly what would your advice be on buying a later 240 parts car and doing the swap, or buying a new/rebuilt transmission and driveshaft online?

 

I don't know if the final drive ratios are different in your old 3 speed.

Me, I would wire up the OD solenoid properly with a control relay as I like being able to force the car into 3rd for hill climbs, down grade engine braking, etc.

oh. later 240's use electronic speedometers, the pickup is a inductance sensor in the differential. I believe earlier ones were mechanical speedometers, and I think the drive cable might have been in the transmission. so swapping transmissions would disable your speedometer.