Transmission service question

[mhb285]

SAE 15w40 or #90 gear oil?
The lube orders in the manuals here at SS are conflicting on this subject.
Thanks
Mike

 

[clinto]

90 weight GL-1

 

[CGarbee]

The military says 90wt (and it's what I am running in both of mine), but when I've talked to Charles at M Series Rebuild, he has told me that is is currently installing a 50wt gear oil (gotta order it from a supplier, not available at WalMart.. ) since that is what Spicer (well, Eaton) recommends these days... He also states that Spicer never actually recommended 90wt for this box, but that the DOD used it in order to simplify inventory/maintenance...

 

[FSBruva]

It is also possible to use a more modern gear oil, but you must be careful... If you go with a GL-5 without the additional MT-1 performance spec, you risk blowing up your synchros. The MT-1 spec certifies that the oil will be friendly to yellow metals.

Matt

 

[mhb285]

well which oil/lube should I be using!

 

[CGarbee]

Pick your favorite brand of 90wt GL1, or GL5/MT1...

 

[FSBruva]

http://steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=10821&highlight=gear+oil

Depends on how you wanna play things!

Technically accurate (per the Lubr Order) = 90 w GL-1, sometimes sold as hydraulic oil for Ford Tractors
Modern equivalent (per API specs) = 90w GL-5 + MT-1
Special order (read: $$$$) = 50 w

Again:

 

[SierraHotel]

I used 90w Gl-1 that I got from NAPA. Went around and around trying to figure which one was best. Finally decided on GL-1 because that is what I took out, what has been used since before I was born and I KNEW it wouldn’t be bad.
Would the GL-5 be a problem with the synchronizers? Got me, but it sound like it might be…from some of the members.
Would the Gl-5/MT-1 work? It should…but then again, I’m no transmission expert.

My final decision was that GL-5/MT-1 might be a better lubricant, but might also bring some problems with it. The GL-1 WILL work; might not be as good, but I know it will not hurt the transmission.
Besides, GL-1 was cheaper …once I found someone that knew what I was talking about.

Now, my question is this:
It says to fill to one knuckle below the fill port. However, the fill port does not even result in filling half of the transmission/transfer/differential. Does it really matter if it is to the filler port or ½ inch down? Isn’t that why there are breather caps? To prevent over pressuring of the fluid?

 

[m-35tom]

i used 30wt non detergent oil in the trans and transfer for 15000 miles with the cat motor, much more power and much more torque and no problems. the 90 wt in the transfer foamed too much at 3900+ rpm. i realize this is not the specified oil, but you do not need the hypoid additive and may get better mileage.

 

[acetomatoco]

GL1... worked well for 60 years....and will continue to do so...foaming is caused by overfilling or blocked vents... fill to one finger knuckle below fill hole....These trucks were designed to run 40 mph in convoy...on non interstate highways... not 60 mph from Chicago to Dallas...

 

[OPCOM]

GL1 is fine for putting around but it does not do as good a job when it gets hot. If you are doing highway driving all day or alot of stop and go, try GL5+MT1.

 

[Recovry4x4]

Ive been using GL1 for many years and many thousand miles and 55 MPH too without issues.

 

[m-35tom]

foaming is caused by me turning the transfer real fast with a .66 overdrive transmission and at 68 mph from baltimore to new mexico. i still use 30 wt in my trucks, easier shifting for one.

 

[mhb285]

Well I changed it. I did put 90wt in it before! O Well.
But I did notice some flakes in the drain pan. Is this normal? No thing but a few little flakes.

 

[Karp]

The guy at O'Reilly's told me that Mystik JT-7 (GL-6) is spouse to be good for the tranny. So I bought a 5 gallon bucket drained my transfer case and filled it then started draining the tranny. I noticed that the oil there was like liquid grease real thick and heavy but the Mystik is red, thinner and lighter. I went ahead and filled it, thinking I would just check when I got home. I have been searching and only found info on using GL5 with MT-1. I'm not sure what I should do, I was going to fill the differentials too but now i'm not sure what to do. thanks for any help.

 

[jasonjc]

Just looked it up. Mystik JT-7 meets the mil spec and the MT-1 spec
http://www.docs.citgo.com/msds_pi/20008.pdf

 

[Karp]

Thanks for the info. I thought I really messed up. But why is it that the old stuff is thick and the new stuff is thinner? I would think that if it was 80-90W gear oil it would be close to the same consistency? Yes I know I'm a newbie on deuce Maint.

 

[acetomatoco]

GL1 was good in 1949 and is still good today...