Gear oil for Diff using Phosphor Bronze washers

[maineSS]

Hi All;

I'm rebuilding a differential for my '49 Power Wagon truck using Phosphor Bronze thrust washers in place of the original fiber ones (which disintegrate over time). Since GL-4 seems to be increasingly difficult to get, I'm wondering what a safe choice would be in today's diff oils- I'd like this rebuild to last awhile, as certain parts are getting hard to come by. I'm a little leery of GL-5's that claim to "buffer" their sulfur content, as the diff can get quite warm in operation at road speeds, as it's quite low geared by today's standard.

 

[dparm]

There are plenty of dual-rated GL4/GL5s. I used them in my Audi S4's manual trans (which needed 75w90 GL4) without any issues.

I used Motul Gear 300, which is a 75w90 carrying dual GL4/5 ratings. Very high VI as well. Held up well to track time.

 

[Loobed]

I think you might need an oil for manual transmissions that have brass synchros.

 

[MolaKule]

If it is not a hypoid differential, I would think any of the Manual Transmission lubes in 75W90 might suffice.

 

[mechtech2]

Use a GL5 - what's the problem?

Or, use steel shims, which is what 99.99999999% of cars use.

 

[maineSS]

Some additions-

This is a hypoid diff, manual transmission oil likely isn't exactly right. Given the expense of the rebuild (over $1000), I'd like to source a product that doesn't use lots of sulfur and rely on an additive to neutralize harmful effects on brass/bronze. The original oil was 90 wt.

With respect to using steel shims, this may or may not work- I'll have to run that by the gear guy. Thanks for everyone's help!

 

[Tempest]

You may want to look into the Chevron ESI gear oils which do not use sulfur compounds:

http://nelsonpetroleum.com/images/delogear.pdf

These are probably industrial lubricants and may be difficult to source is small amounts.

 

[dailydriver]

Originally Posted By: Tempest
You may want to look into the Chevron ESI gear oils which do not use sulfur compounds:

http://nelsonpetroleum.com/images/delogear.pdf

These are probably industrial lubricants and may be difficult to source is small amounts.


Beat me to it.

Yes, they use a boron/borate EP add pack, instead of a sulfur type.

 

[tdi-rick]

I would have thought a buffered GL5 with a copper corrosion number of 1b would be fine.

 

[mechtech2]

http://www.smokinvette.com/corvette/articles/a-study-of-automotive-gear-lubes-part-2/

This has been posted in BITOG a number of times.
It shows bufered types are great for stopping corrosion.

Note the only ones to fail copper corrosion are LUCAS and ROYAL PURPLE - Chrysler stuff was not great, either. But who goes out and buys Chrysler fluid anyways? I think Royal POIPLE is to be avoided, anyways.

 

[maineSS]

I looked at the ASTM D-130 part of the "Automotive Gear Lube Study" (Copper Corrosion Test), and see that NONE of the tested oils pass the 1a classification- which is what I'd want. Also, there's no mention of the type or percentage of EP additives each oil has, which makes the corrosion data difficult to evaluate. I'm assuming these are GL-5 oils- as the classification isn't mentioned, either? Otherwise, it's a good writeup of testing methodology.

 

[maineSS]

After reading Part 1 of the Automotive Gear Lube study, I see it's written by Amsoil- no wonder their oil did so well! At least they identified themselves, in other cases you have to rely on your internal [censored] meter.

I came across a post by Spitty in the thread "GL-4 vs GL-5..And a Letter From Mobil" in the archives (5th post) https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=511744... that relates to my situation. Spitty apparently was using 1995-era GL-5 in a Triumph diff with bronze thrust washers, which entirely disappeared after 9 years use. Now 9 years sounds like a long time, but if the car was used only for summertime highway driving, that wouldn't be very many hours before complete failure. Hence my skepticism about "buffering" claims. Since the original diff made it 64 years on oil vastly inferior to today's product, I'd like to think I can go another 64 on the correct lube.

 

[mechtech2]

maine-

9 years on new washers? Or 64 accumulated total? I have lots of questions about that rear end.


GL4 is not sulfur free, you know. About 1/3 as much as GL5. It is not a cure all,just better in the right direction.

 

[maineSS]

Mechtech-

My diff is the one with 64 years on it, it came with fiber thrust washers, which, judging by debris in the axletubes, may not be there anymore. Spitty's Triumph diff was rebuilt with bronze washers, which disappeared after 9 years use. I definitely don't want a replay of his experience.

I'm hearing good things about Chevron's Delo gear oil, wonder why Amsoil didn't include it in their test?

 

[SS1970chrysler]

I use Coastal GL-4 in my vehicles of that era. 80w-90 in the axle, and 85w-140 in the gearbox. Vehicles are 1948 Packard and 1941 Studebaker all still on factory assemblies.

 

[maineSS]

I did some further checking on Delo, and found that its ASTM d-130 number is 2a- surprising in view of its boron chemistry supposedly being "non-reactive" with metal, according to the Chevron Delo website. Is 1b is as good as diff gear oil gets?

 

[tdi-rick]

OK, is it a hypoid CWP ?

If so, you'll need a GL5.

If it's a spiral bevel CWP you'll get away with a tough GL4, although I can't state strongly enough how a decent GL5 will extend crownwheel life in a spiral bevel diff.

 

[maineSS]

What would be your definition of a hypoid diff? This one looks like it might be a "high pinion" spiral bevel gear.

 

[SS1970chrysler]

In '49 the gearset was changed from 4.8? to 5.8? for durability and power, so you could have either set.

 

[mechtech2]

Originally Posted By: tdi-rick
OK, is it a hypoid CWP ?

If so, you'll need a GL5.

If it's a spiral bevel CWP you'll get away with a tough GL4, although I can't state strongly enough how a decent GL5 will extend crownwheel life in a spiral bevel diff.


A hypoid gearset IS spiral bevel. One version.