I'm looking into buying an overdrive tranny and am wondering people's opinions on the earlier M41s? I found a shop selling both and he wants about half as much for the 'older' style. I'm wondering what the difference really is in toughness?

Hello,

The early overdrive units fitted to the M41 are referred to as "D" and the later overdrive is called a "J".

The overdrives are NOT directly interchangeable as they use different mainshafts.

But a lot of the other internals of the 4 speed part of the transmission are interchangeable.

"D"s have almost 30% overdrive, while the "J"s are only a little over 20%.

The "D" is weaker and replacement parts can be harder to find especially hard parts like planetary gears and clutches.

FYI, it will make your life way easier if you decide for the "J", to make sure you get the SMALL diameter output flange.

The "D" output flange will NOT work on a "J".
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502

Amen to the bit about the J-sized small-output flange. That thing is difficult to source. In my limited experience, the M41J overdrives are found on the later 1800 and 140 series cars using the 2" driveshaft.

If you can't find the proper flange from the seller, or Eric, try contacting P1800.com. That's where I found mine.

So the J's come in both larger and smaller output flanges?

Eric,

I once had to replace the M-40 (no O/D) in our 72 144, with a slightly older version from a junk yard. As I recall they said it was from something like a 69. Same spline count on the front end. The only difference I could see within the gearbox itself was that the reverse idler gear on the newer ran on needle bearings and the older ran on a solid bushing - I think that's how it went. Do you know what year that switch was made?

I did not know that the J and D had different ratios,,,,FWIW I have a J and the ratio is long enough....went 100 mph without redlining.... still had a little pull left, but I was too chicken.
--
Patrick, '68 220 (used to drive 240s)