What gear lube isbest for my T-85 O.D. gearbox?
The 1950s B/W manual says SAE 40 or 50wt motor oil of "goodquality". (It doesn't say detergent or non.)
OR Transmissiontype mineral oil 80 or 90wt.
I'm considering Lucas 50wt synthetictransmission oil.

Anyrecommendations?
Thanks

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I use plain 'ol 90 wt non-hypoid. I'd be hesitant to use a synthetic for 2 reasons: most of them are hypoid oils. The additives that make them suitable for diffs can attack the yellow metals, i.e. the sychronizers, in the transmission. The other reason is synthetics will find leaks that regular gear oil would never see. These are tough old boxes but but they just weren't sealed as well as a modern transmission. JMHO. When filling be sure to remove both fill plugs. Fill the transmission section 1st, then top up the OD section. 

80-90 gearoil best according to warner,as auto trans or synthetics will hinder synchronizers operation.same goes  for the old 3speeds

This topic has been covered before.  John F. (The Hoosier Hurricane) had authoritative information that he related.  Borg Warner called for mineral oil for their manual transmissions and overdrive units.  Apparently there's a friction factor to mineral oil that is important for the optimum operation of the synchronizers.

I wish I could easily put my finger on the earlier thread, BUT.  Unfortunately, John won't be chiming in on this.  Frank Rice has indicated that John is having computer problems.

The previous thread went on to talk about the ridiculous price that mineral oil was going for.  Too, I recall the comment that mineral oil is not available everywhere.  My recollection is that John said that the best price he had found was at a local Tractor Supply Store and that their price was significantly less than what he'd been quoted other places.

In checking Tractor Supply on the Internet, the product name that came up was, 'Traveller Ford Tractor All Mineral 90 Transmission Fluid'  2 gallon plastic pour container, $17.99   Their item number is 080660099.

Hope this helps. 


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

NAPA also has it but prolly at a higher price.

Thanks everyone!
Looks like I'll be going with straight 90wt mineral oil. I'll make a run today to the local TSC and pick some up.
I gotta say that I love this gearbox. I'm running it behind a mild 312  with a 4.30 traction loc in my '57. (3.01 in O.D.)
With a ECZ Carter AFB I'm getting around 18 MPG @ 70-75 MPH and 12 to 14 in town on 89 octane. Not too bad.
I hope that these current gas prices hold up through the summer...I'd like to open up the secondaries more often.



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