I am trying to determine a noise that seems to be dependent on ground speed and is more noticable as speed increases. The transmission has been in my 72 142E for some time but I just recently eliminated some of the wind noise making the transmission noise, I guess, more pronounced.

How can I tell for sure if the M41 is making the noise? I take the car up to 70 or so then disengage the clutch to eliminate the engine noise. The noise is about the same in or out of overdrive. Is it typical for bearings to get loud in an M41? Currently I am using ATF. Would heavier oil help? At some point I will pull the motor for an overhaul but would hate to damage the M41 in the process of driving the car until then.

Thanks for the help-
Mark Richardson

Hey, Thanks for all the help! The u-joints are new along with a shortened and balanced drive shaft. Also carrier and pilot bearings are new.

So,I guess trying an oil switch would be a good first try. I should have added that the noise is the same with the rear end off the ground so that rules out a front wheel bearing.

My original 72 142 with an M40 is at 335K and no noticable tranny noise. Of course the engine is getting a little loud but I it seems quiet during the clutch released at speed test. Always ran 80-90 weight. I sometimes thought it was a bad idea having 80-90 in it on below zero morning when the car started to move forward after starting when clutch was engaged. Didn't try to go far but just inched ahead a little.

Mark Richardson

I got my 164 with M410 and OD about 6 years ago. Initially I used 30 weight engine oil which worked fine except shifting got sluggish in cold weather. I have since switched to Redline MTL which seems superior to me because it flows more easily...easier shifting when cold.....and it has reduced a tendency for the shifter to catch when shifting into 1st and 2nd. My guess is its the pilot bearing which will get changed when a new clutch is needed.

Regardless of what the manual says, I use 80/90 gear oil in my M41. Hey, it works for Irv Gordon, Art Banks and other high-milers. I've never encountered anyone who had any trouble as a result. Quiets things down and stays inside a lot better.

Definitely do NOT use ATF unless the OD case is stamped "ATF." That's only appropriate for later ODs on M46 trannies.

I've heard good things about Redline MTL or Motul, but haven't tried them yet myself.

Swede, the local mechanic/guru from Sweden, told me years ago "gear oil for der Pacific Nordvest-Tirty veight for Sveden".
The fact that Irv uses it (and can tell the difference in his car)...

Hi Mark;

I have replaced many output shaft bearings in the M40 and M41 transmissions. They will produce a noise whether the engine is loading the drivetrain or not. The bearing is inexpensive new, but getting to it takes a bit of labour for sure.
Both 30W engine oil and ATF are fine in these gearboxes - but if the bearing is bad, then neither will correct it, and at best mask it until it gets even worse. The metal particles produced by the bad roller bearing will find their way into the overdrive unit, and make more damage. My advice would be to fix the problem now when it will still be simple and cheap to do so.
Rhys

I used Redline MTL and it help a lot.

... That reminds me of an ol Peugeot 404, my first car. I put a roof rack on it and it developed a most pronounced wind howl. In my ignorance, I diagnosed the noise as coming from the rear end. One of many lessons at Ye Ol School O Hard Knockers!

My 70 owner's manual says to use engine oil in the M41. ATF is a lot thinner than engine oil. I'd switch to RedLine 30W synthetic. If you notice a change in noise after changing to the thicker oil, then you've located the source - or at least one source.

I'd consider other easier stuff first, before ripping into the M41. Driveshaft U-joints will vibrate and growl before the needles fall completely out. Also, ds center support bearing is suspect. So are rear end input bearing and wheel bearings. (Diffy gear noise is not constant and changes w/ throttle-on or throttle-off.)

Good luck!
Al

My howl was still there after re-building my M41, turned out to be front right wheel bearing. The sound was coming right up out of the tunnel. Oh well.