Gear oil recommendations for German army truck

[roburswest]

Hi everybody.

My vehicle is a 1974 East German Military troop transport. 2 ton running gear, 4x4, all low end torque. Top speed of about 50mph. I am replacing the fluids and looking for suggestions. Here are the owners manual recommendations:

Transmission - 3.65L of SAE 90
Transfer Case - 1.5L of SAE 90
Differentials - .8L of SAE 90 - SAE 140
Steering Box - 1L of SAE 80

Is it wise to switch to synthetic gear oil? Also can I use the same oil for all four?

Thanks.

 

[unDummy]

Transmission/transfer case: any SAE50 from this list:
http://www.macktrucks.com/assets/mack/approved_lubs/Mack_Trucks_Approved_TO-A_Plus_List_Rev1.pdf

Any full synthetic 75w110 or 75w140 for the differentials.

Steering box hydraulic fluid, any full synthetic ATF or PSF.

 

[roburswest]

ok 75w140 for the diffs. Why sae 50 for the tranny when it calls for sae 90? I dont fully understand how gear oil is rated.

 

[rclint]

As to the synthetic question here, my answer will be different than the answer I gave to you dealing with synthetics for your engine.. reason being is contamination from combustion, and drain interval. Transmission, and steering box oils just don't see the contamination a engine does so it is at least worth looking at the option of using synthetic. Then you also have to look at just the quality of lubricants today compared to when this truck/transport was built are day, and night.. Lubricants have come a longgg way, conventional lubricants would work find here, but the option of using a synthetic is sure tempting as your will likely not have to change them again for many many years.

The only things that come to my mind are how dirty the diff/trans/steering box are, and how much the lubricant you choose is going to cost.. Some things you could probably clean fairly well such as the differential, others like the steering box would be better server to do fluid change, then another shortly after to clean it that way. I'm not sure how much truth is in the rumors of synthetic fluids causing leaks, and I hardly ever say anything like this, but this being a really heavy duty vehicle, and the fact that parts may be extremely expensive, and hard to get I want to at least throw that information in your direction... If it were me, and I planned on keeping/using this vehicle (if you could call it that) I would use synthetics in these areas (but not in the engine as I posted in your other thread).

 

[m37charlie]

Originally Posted By: roburswest
ok 75w140 for the diffs. Why sae 50 for the tranny when it calls for sae 90? I dont fully understand how gear oil is rated.


This
http://www.mobil.com/USA-English/Lubes/P...n_Fluid_50.aspx
is Delvac Synthetic Trans Fluid 50. It is essentially a heavy 75W90 but it is GL4 designed for transmissions rather than a GL5 for diffs. I believe it is at the top of the heap as far as heavy truck trans oils and many other mfgs buy base oil from ExxonMobil to put their own additives in their 50 wt trans oils. The "50" refers to its' viscosity at 100C. compared to 50 engine oil. Since it is synthetic its' pour point is -45C.

Charlie

 

[unDummy]

There's a difference between SAE J300 and SAE J306 labeling. To prevent wrong fluids from being used in rear-ends, transfer cases, manual transmissions, and engines.... the bottle labels need to be a little different, otherwise they'd all say SAE90 everywhere and confuse the mechanic.

The SAE-50's in the list above are equivalent to a SAE-90 and some are close to a SAE-110. Great protection for worked manual transmissions.

If the shift quality is a little difficult, you can use a GL4 75w90 manual transmission fluid. Amsoil MTG, Redline MT90, and Ford XT-4-QGL are your other options. SAE 75w90 manual transmission fluids are usually SAE40.

Since you give no details to the year, make, model, component type..... I'll stick with truck fluids over car fluids for retired military vehicles.

 

[roburswest]

Sorry. Its a 1974, Robur LO2002A. 2-ton running gear, air cooled gas engine.

 

[unDummy]

Interesting vehicle. If you still have 'factory fill' or foreign fluids, you might want to send out the old fluids for an analysis to see what it originally came with.

Unless you want to free up a couple of HP/MPG, there isn't a real need to use a synthetic. The synthetic benefit also helps in the extreme cold or hot too. But, because of cost, some don't want to change it or top off as needed.

If vehicle is used in off-roading and crosses rivers/streams, or if you water dunk the power-train, cheaper gear oils changed more frequently is always better than water logged exotic oils. Do you treat it like a submarine? If not, use the synthetic.

I'd stick with the SAE-50 in the manual. Can't go wrong with a 75w140 in the differentials.

And, concerning the steering, because some newer universal/multivehicle ATFs may possibly not be friendly with older seals, use a full synthetic Type-F, PSF, or racing ATF.
Some steering fluid choices:
http://www.redlineoil.com/product.aspx?pid=52&pcid=9
http://www.amsoil.com/storefront/art.aspx
http://www.redlineoil.com/product.aspx?pid=79&pcid=27
http://www.amsoil.com/storefront/psf.aspx
http://royalpurple.com/prod-pdfs/max-ez-ps.pdf
http://www.sweetmfg.biz/products2.asp?edit_id=28

If you take it swimming:
Napa usually stocks and can get the 85w90 GL4 Stalube/CRC gear oil which is probably the cheapest MT fluid available. Other SAE90 gear oils are the lower-end outboard marine gear oils.
Any mineral 80w90, 85w140, or 80w140 would be cheap and effective in the differentials if changed appropriately.
Also should be plenty of generic PSF choices at the local autopart store. Just make sure it meets any of the Ford, GM, Mopar, or Honda spec's and you should be good for the PS system.