M35A2 Transmission Fluid Change

[Dasgog]

Well i bought SAE 40 ND last week planning to change my transmission and tcase fluid to it, but after finding this thread I'm not so sure. Anyone else have more input on the topic?

I know, right?
I ended up using 85w140 for Trans, Transfer and Axles. Not sure if it was right but it’s been months and I see no issues, thus far.

 

[NY Tom]

Lot of input above. Varying opinions of course. Trucks vary too... I would give it a shot in the transmission. See how it shifts.

As for the transfer case I stuck with 80W-90 gear oil and it was fine. Previous owner had 85W-140 or whatever in it and in the cold it would grind while shifting until it warmed up. Of course it leaked after I changed it. Probably why they were running the thick stuff.

 

[NebraskaFan]

I know, right?
I ended up using 85w140 for Trans, Transfer and Axles. Not sure if it was right but it’s been months and I see no issues, thus far.

My trans has 80/90 in it now, I'm leaning towards sticking with that or going 75/90 for better winter shifting. It shifts fine now, aside from being sluggish in the cold. I thought the viscosity was lower on the SAE 40 when i bought it, but after finding this thread and researching more mfg viscosity ratings on it vs 80/90 etc i see no real benefit to straight 40.

 

[Dasgog]

My trans has 80/90 in it now, I'm leaning towards sticking with that or going 75/90 for better winter shifting. It shifts fine now, aside from being sluggish in the cold. I thought the viscosity was lower on the SAE 40 when i bought it, but after finding this thread and researching more mfg viscosity ratings on it vs 80/90 etc i see no real benefit to straight 40.

I am in Arizona and aside from a cold month or so it’s generally 80’s and now for 2 months it’s in the 100’s. I am only using 85w140 cause it’s good at higher temps in the gears and I have to assume it gets hot in there. But at the end of the day, I really don’t know.

 

[NebraskaFan]

Lot of input above. Varying opinions of course. Trucks vary too... I would give it a shot in the transmission. See how it shifts.

As for the transfer case I stuck with 80W-90 gear oil and it was fine. Previous owner had 85W-140 or whatever in it and in the cold it would grind while shifting until it warmed up. Of course it leaked after I changed it. Probably why they were running the thick stuff.

I guess that's a fair point.. I didn't keep the receipt so i guess i may as well try it in the trans. Tcase i might just go straight to 75/90.

 

[frank8003]

You could put Cannola oil in it.
Get your self some new squish washers for the fill and drain and keep changing it out until YOU satisfies what is best for You and yours.

 

[Dasgog]

I guess that's a fair point.. I didn't keep the receipt so i guess i may as well try it in the trans. Tcase i might just go straight to 75/90.

Out here there’s an older guy who owns 10’s upon 10’s of acres of Military vehicles, I’m talking hundreds of M35A2 etc and he’s also a mechanic etc and he str8 up says he uses 85w140 for Trans, Transfer and Axles and then Straight 40 for Oil snd his comments were cause it’s always hot out here.

 

[frank8003]

Out here there’s an older guy who owns 10’s upon 10’s of acres of Military vehicles, I’m talking hundreds of M35A2 etc and he’s also a mechanic etc and he str8 up says he uses 85w140 for Trans, Transfer and Axles and then Straight 40 for Oil snd his comments were cause it’s always hot out here.

Where is HE?

 

[NebraskaFan]

Out here there’s an older guy who owns 10’s upon 10’s of acres of Military vehicles, I’m talking hundreds of M35A2 etc and he’s also a mechanic etc and he str8 up says he uses 85w140 for Trans, Transfer and Axles and then Straight 40 for Oil snd his comments were cause it’s always hot out here.

I'm a little worried how that would work when its below zero haha. Based off the the chart posted on page 1 75 or 80w - 90 is probably my best bet for all around usefulness. Maybe I'll see if bomgaars will take the 40 sae back without a receipt.

 

[Dasgog]

Where is HE?

Tucson, AZ

 

[frank8003]

I'm a little worried how that would work when its below zero haha. Based off the the chart posted on page 1 75 or 80w - 90 is probably my best bet for all around usefulness. Maybe I'll see if bomgaars will take the 40 sae back without a receipt.

Gooly
You ain' listening
Just put whatever NEW stuff you got in there and drive it around. A few hundred shifts up and down and using doublecluth transfer case method.
How would You know unless you used it?

Take the drain transmissinon transfer case oil and put it thru your very best 3 micron filters and burn it up. You paid for that fuel now use it.

 

[Katavic918]

Well i bought SAE 40 ND last week planning to change my transmission and tcase fluid to it, but after finding this thread I'm not so sure. Anyone else have more input on the topic?

I had 40 nd in my last deuce for a month or so. It shifted fine but when I went to 90w mineral gear oil it felt like the gears were a little more cushioned if that makes sense. I could feel the gears less through the shifter. Just my observation.

 

[NebraskaFan]

Gooly
You ain' listening
Just put whatever NEW stuff you go in there and drive it around. A ew hundred shifts up and down and using doublecluth transfer case method.
How would Youy know unless you used it?

Take the drain transmissinon transfer case oil and put it thru your very best 3 micron filters and burn it up. You paid dor that fuel now use it.

Haha I'm hearing ya. My main concern is the pour point of the sae 40, but i suppose if its double digit negative i can just slap some pan heaters on the trans and tcase.

 

[frank8003]

It is so easy to change out and you can burn it

 

[NebraskaFan]

It is so easy to change out and you can burn it

Yeah I'm not so concerned about draining and replacing, but I don't have anything to filter to burn it. So then I'm just stuck with more waste oil sitting around lol. Small problem though. I'll give it a shot and report back.

 

[frank8003]

Golly filters are easy to set up.
If the trash oil has wisps of silver in it don't use it.
A really good hydraulic cloth is what you need to use or a good filter and a pump. Don't keep "waste oil" around, just use it up. That is Why You have a multi-fue;l.

 

[M37M35]

I just recently changed mine and put 80/90 GL4 back in it. So far, so good.

 

[NebraskaFan]

As another update here.. I put about 100 miles or so on the 40 wt ND oil, and maybe it was just chance but it immediately started leaking from the rear main seal (well not quite immediately, I think it started once it was warmed up), at least as far as I can tell that's where it was coming from. I lost probably 3 qts before I noticed it (yikes). I've since refilled with 80w/90 so we'll see what happens next time I drive it. Going to give it a good look over to make sure there isn't something I missed.

 

[V8srfun]

I just put mobil1 50 wt in my trans but in the process I found bad news.
To fill it back up I decided to pup the top cover off instead of messing with filling through the fill plug. And I noticed that about 25/30 percent of the leading edge of the teeth on first gear are broken off. And fourth was looking worn. Then I also noticed that the fluid I removed was the thickest gear oil I ever seen in my life.
Now I have a harder with fourth gear than I did before but everything else seems the same shifting. If I would have known about the damage to the trans before I would have waited to change the fluid but now I am deciding on if I will repair or replace the trans. I suspect that the thick fluid was installed by the previous owner because of the damage but who knows.

 

[NebraskaFan]

I just put mobil1 50 wt in my trans but in the process I found bad news.
To fill it back up I decided to pup the top cover off instead of messing with filling through the fill plug. And I noticed that about 25/30 percent of the leading edge of the teeth on first gear are broken off. And fourth was looking worn. Then I also noticed that the fluid I removed was the thickest gear oil I ever seen in my life.
Now I have a harder with fourth gear than I did before but everything else seems the same shifting. If I would have known about the damage to the trans before I would have waited to change the fluid but now I am deciding on if I will repair or replace the trans. I suspect that the thick fluid was installed by the previous owner because of the damage but who knows.

Damn that sucks... Is that their 50 wt synthetic? Seems strange that the heavier oil would make it shift easier.. either way quite unfortunate.