Trans oil

Start oil threads here so they can be ignored and/or ridiculed by most of us (except for those hardcore few that live for that kinda stuff).
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Here's the place for you to debate what oil is best. Post your oil related topics her so we don't clutter up the other sections. Most people avoid oil threads like the plague.
Hero of the Soviet Union - 2018
Hero of the Soviet Union - 2018
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Re: Trans oil

Post by hotflash44 » Thu Jul 13, 2017 8:35 am

Bilgekeeldave not trying to dispute what your saying about the old British cars,i have had several in the day. but i cant remember a American made transmission that ever used engine oil. Not sure in the olden days people other than some engineers knew much about gear pressure/sheer. The oil experts say that the gears actually slice up the molecules over time, and cause the oil to become less effective. Thats why modern transmission oil was invented. The above is why some Uralistas have trouble wrapping their brains around the concept of 20/50 oil in everything ,but Ural has done this for years, go figure!
drive a 2016 gear up asphalt grey .Air America CIA circa 1967/8 Vung Tau Viet Nam USS Tutuila ARG-4 (AND JUST A TOUCH OF AGENT ORANGE!)

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Re: Trans oil

Post by GregAus » Sat Jul 15, 2017 11:17 pm

Ural hasn't recommended 20W50 for that long. Original specs were for Soviet oils that were 8 Centistoke (at 100˚C) in winter and 12 Centistoke (at 100˚C) in summer, equivalent to SAE20 and SAE30. Later they recommended SAE20W30. CSMI, the original Ural importer to the US was probably the first to recommend 20W50 in engine and gearbox. (Probably because BMW used 20W50 and "everyone" knows that Urals are copies of BMWs).

Since then almost everyone has recommended 20W50 in both engine and gearbox with the exception of the previous German importer Haubrich who recommended 80W90 in the gearbox. It seems that the COC in the UK are also recommending 75W85 or 75W90 in the gearbox. Two-smoke motocrossers often run ATF in their gearboxes due to the wet clutch and it works well and has a viscosity of generally 7-8 Centistoke (at 100˚C). Looking online most gear oils 75W90 and 80W90 have a viscosity of 14-15 Centistoke (at 100˚C). Redline MTL 70-80 only has a viscosity of 10.6 Centistoke (at 100˚C).

Using gear oil won't hurt your gearbox, except in increased fuel consumption and additional cost, but it probably won't help it except psychologically. Me I run 15W40 diesel oil in both engine and gearbox, changing engine at 2,500 km in the M-63 (slingers only) and 5,000 km in the M-67 (oil filter and slingers). Gearbox oil and FD oil is changed at 5,000 km. The manual says 10,000 km for the FD, but it works hard and it's just as easy to do with the engine and gearbox.

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