Thanks all, for the info on the gear oil , sounds like the SAE30 is the way to go.

I have been thinking the idea over of rebuilding the transmission next year.
I was considering taking the M41 apart, obtaining new bearings and synchro rings and using whatever parts I can from a less worn M40.

I have a second M41,well the back half of it, the case is snapped off, 9 owner used overdrive in reverse by accident, or so i was told. and the mainshaft is gone, but the od clutch parts may be intact. i only have the one long mainshaft and it is in my car.

the tranny still shifts ok , just getting a little noisy. has anyone else tried this? and will most everything swap over, less the longer mainshaft?
it seems it isn't hard to find good M40's for the parts, but the M41's are harder to find. If all the gears and bearings can be swapped over it might make it easier to finish up with a half decent one without going for broke.

phil

Do you know hwat years the gearboxes came from? There are at least two, maybe three slightly different variations of M40/41. Some parts are interchangeable. Some are most definitely not.

--
-Matt '70 145s, '65 1800s, '66 122s wagon, others inc. '53 XK120 FHC

I am unsure of the year.
the broken overdrive was from a 122 from england.
the one in my car is from a 123gt but I don't know what year.
guessing.... all these parts are from 66 to 69

I have several standard trannys, they all look the same.
I would be interested to know more about these differences before taking mine off the road to find out the parts swap won't work as anticipated.

thanks,
Phil

Yep. Last winter I tried the same thing - mixing and matching parts from my PV's original and good shape M40 and it's new junkyard M41 (with, as it turned out, totally non op 11 and 3 syncros).

To make a long story short, in the end the *ONLY* parts that I could swap were the syncros. Luckily enough, those were the only parts I really needed. I think this is more a matter of the year of the transmission than an M40/M41 difference, generally an M41 will be newer as they slowly became more popular in later model eyars.
--
I'm JohnMc, and I approved this message.