Diff only Oil

[panhead_pete]

Hoping not to start another oil thread that goes south. I need some oil for the rear end of my coupe. It has a later gearbox so I only need it for the Diff. I do not have access to 600W here in Japan. Having read lots of posts and now having 'paralysis through over analysis' Am I good to use 85W140?

https://www.monotaro.com/p/5565/8645



https://www.amazon.co.jp/-/en/TAKUMI-85W-140-Compatible-Synthetic-Racing/dp/B075TTM9XG


Thanks.

 

[Bob Bidonde]

I have been using SAE 75W145 GL4 & GL5 Gear Oils for many years without issues. 85W140 is a good choice.

 

[rotorwrench]

The GL5 multi-viscosity is fine in any rear axle that doesn't have soft metals like brass or babbitt in there for thrust washers and such. It's over kill but it won't do any harm. Since the banjo style rear axles of the model A era and later through 1948 are not Hypoid type gears, they can use GL1 rated gear lubes just like an old tractor or a worm screw drive. The model T rear axle is an exception that had soft metal thrust washers so it has to use GL1 or no more than GL4 rated lubricants.

Straight grade would be what was originally used but multi-vis likely won't have a leak problem on a banjo rear. The parting gaskets and axle seals do a fair job of holding lube in there. If a person parks downhill on a steep grade, some lube can migrate up to the U-joint area but it generally flows back in during normal operation or when parking in an uphill direction.

 

[panhead_pete]

Thanks very much gents, will order some today.

 

[CT Jack]

I would go with the 85W140 and add some John Deere Corn Head grease. The Corn Head grease will add a little more viscosity to the gear oil. It has a unique property than is different than most grease. When it warms up its viscosity lowers thereby when combined with the gear oil it provides a uniform lubricating film on gear teeth and bearings.

 

[Synchro909]

I would go with the 85W140 and add some John Deere Corn Head grease. The Corn Head grease will add a little more viscosity to the gear oil. It has a unique property than is different than most grease. When it warms up its viscosity lowers thereby when combined with the gear oil it provides a uniform lubricating film on gear teeth and bearings.

I concur with this one but I think ordinary grease would also be fine. It would mix with the oil and stay mixed. STP or similar would also achieve the higher viscosity desirable.

 

[Chris in WNC]

I ran straight STP in differential, transmission and steering box for many years with no problems.
Hard to get it into the differential, a 90 degree street elbow screwed into the fill hole helps.