M939 What Fluid for Trans/Pwr Stg?

[rneely]

New to M939 and looking in the TM they say to use OE/HDO 10 for Power Steering and OE/HDO 10 for the Trans (per Lube Order) but OE/HDO 15/40 per TM.
My question is what is OE/HDO 10 and OE/HDO 15/40?

What brand of power steering fluid is correct and what brand of auto trans is correct?

 

[juanprado]

I would use plain ole power stg fluid instead of 10w motor oil. Power stg or hydraulic oil has anti foam and other additives and is better than motor oil for power steering applications.

15w40 is engine oil. Any name brand diesel approved should be ok. I believe in combat it is an alternative to 10w.

The military uses motor oil in the transmission or dexron transmission ATF. Check your dipstick to see if it is redish (atf) or yellow/brownish like motor oil. Many threads here about it. Draw your own conclusions but I think Dexron is the way to go as it has the proper additives for auto trans and motor oil does not. Allision has their own proprietary trans fluid they recommend and it is pricey.

Mine came with dexron. If it did not, I would have flushed it and changed all filters then refilled with Dexron.

 

[wsucougarx]

What Juan said!

 

[bsteinborn]

rneely, you ever get the power steering fluid replaced? An M939 newbie myself, the power steering was giving me fits this past weekend. The power steering reservoir is low but since I don't know if it has 10w motor oil or power steering fluid I figured I'd just drain the system and replace. Looked through the TM's today but couldn't find anything related to draining the power steering fluid. Do you you where the drain is for the power steering system? Thanks!

Bryan

 

[two.fiveM35]

Anyone know where to get 10w oil? Checked with NAPA and 20w was their lowest.

 

[Guns]

Tractor Supply carries it. Think the brand name is 'Traveler'

 

[rneely]

See LO 9-2320-211-12 for instructions

 

[trooper632]

Juan, did you flush your tranny yourself or have it done before going with dextron. Mine has motor oil in it and I was thinking about changing it although it shifts just fine

 

[jw4x4]

Anyone know where to get 10w oil? Checked with NAPA and 20w was their lowest.

10w oil is also known as hydraulic fluid.

 

[juanprado]

Mine came from Fort Polk already with dexron. I just changed the spin on filter and topped it off. Mine shifts very smoothly.

 

[M35A2-AZ]

My M936 came with Dexron and all my other trucks had 10w in them.

 

[Dmaxcc6spd]

I was considering making the switch at ATF. I spoke with a local Allison mechanic and he suggested leaving the motor oil in the trans as it has better heat resistance properties. Now I'm really confused.

 

[timass1]

I JUST GOT MY M925 AND THE DIPSTICK ON THE TRANS WAS DRY. wHEN i UNLOADED OF THE TRUCK AND DROVE IT UP AND BACK IT SEEMED TO SHIFT NICELY. SO IM LOOKING AROUND FOR A SUITABLE OIL TO TOP OFF AND SEE WHAT LEAKS. i WAS LOOKING AT TRACTOR SUPPLY TODAY BUT WANTED TO FIND MORE INFO BEFORE PURCHASING. I SEEN THE TRAVELERS BRAND IT DID SAY ALLISON C-3,4 SO WE'LL KEEP LOOKING FOR MORE INFO.

 

[timass1]

aNYONE HERE EVER USE THE LUCAS ADDITIVE FOR HYDRAULIC/10W APPLICATIONS. I ADD IT TO MY OIL NEEDS ON MY DUECE BUT WAS CURIOUS AS TO USING IT ON THE 5TON TRANS. ANY INPUT WOULD BE APPRECIATED.

 

[emr]

A search would have all these questions answered. It has been stated the 10 wt is for extreme service, Stated by Allison. And as stated correctly above, 10 wt is hydraulic oil. It is perfect for everything it is used for in these trucks, But hey its your truck always do what you want. But...This particular model has more in service miles than any other Mil truck in History. All its fluids, and mechanical parts have more than proven themselves in every climate on this planet, over and over again, Just an fyi...

Oh and for Lucas, additives do work , Lucas is a good one, I throw a gal in my 80/90 5 gal pails for my diffs and other places for that oil, I use it in engine and yes in the trans, Using products to enhance the product used in my view is good. But to be honest not necessary . But for me it is a good product and worth it.

 

[timass1]

Thanks for the input emr. I think I'll start with 10w to see where the leak is and then go from there. I will probably head up to the allison dealer to get some ball park prices on services. Thanks again.

 

[timass1]

To my suprise the trans fluid was just low enough not to read on the dip stick. I added some lucas hydraulic additive. I ran it a few miles to see if the temp gauge was actually working it took some time but it appeared to be showing. I need to run it some more and monitor this as well as the fluid level. I still need to check the shift points via the rpm table to see if it needs any adjustments.

 

[hank2424]

what type dextron do you use?? thinking of changing mine also.

 

[M35A2-AZ]

If your going to switch fluid you need to use Dextron III.

 

[TacticalDoc]

Looked up a lot of old posts and just called 2 Allison Trans Service shops. spoke to them about the MT654CR which is not electric. Both recommended that 10w40 should be fine and they wouldn't change it to Dex3. One said Dex 3 is no longer recommended in Allison trans because it does something to the seals. and the other also did not recommend Dex 3. The difference is that the 10w40 is thicker and doesn't have the additives.

My solution is to use 10w40 for everything (steering, trans and motor except axles) and add a preservative like lucas or Sea Foam to it. As they both said the military have been using it for years on non electronic transmissions with success and that's what I'm going to do.