Best Gear Lube for 1937 Terraplane Transmission? (GL1 vs. GL4?)

igrout

Hello, I am helping my dad with some end of season maintainance on his 1937 Hudson Terraplane, and we want to change the transmission oil.

I don't know a lot about Hudson's but I have heard that the new formulation of GL4/GL5 90 weight gear lube sold as the standard "general purpose" gear lube in auto parts stores eats the brass and other yellow metal parts in older transmissions.

I wanted to ask the community what is the best Gear Lube for this Terraplane transmission? The manual says 90 weight gear lube. Does the Terraplane transmission and Rear End have yellow metals that affected by the new GL-5 compatible formula?

I was thinking GL-1 NAPA Straight Mineral Gear Oil 90 weight 

https://www.napaonline.com/en/p/FNJ65201

or

A Yellow Metals safe GL-4 like this Sta-Lube SL24229 API/GL-4 Multi-Purpose Gear Oil,

https://www.amazon.com/Sta-Lube-SL24229-Multi-Purpose-SAE-QT-Fluid_Ounces/dp/B000KKHO86/ref=pd_lpo_200_t_0/130-7227503-3610101?_encoding=UTF8&pd_rd_i=B000KKHO86&pd_rd_r=f58a03c5-cfbb-4f31-86fa-a321c3f59cbd&pd_rd_w=ZKmVo&pd_rd_wg=Zu8EH&pf_rd_p=7b36d496-f366-4631-94d3-61b87b52511b&pf_rd_r=41C5YSMYJX0PSES94WVD&psc=1&refRID=41C5YSMYJX0PSES94WVD#customerReviews


A secondary question, does the rear end also have the same "yellow metals" compatibility issue? Do folks have a recommendation for that as well? 

Thank you in advance for your help.

Thanks and Best Regards,

Ian Grout

Old Fogey UK

There's a Castrol Classic oil that's OK.

Ric West IN

Stick with the GL 1 for both trans and rear end.  NAPA was close to me.

bob ward

QUOTE  Does the Terraplane transmission and Rear End have yellow metals that affected by the new GL-5 compatible formula?

The cupped thrust washers behind the spider gears in the CWP may be bronze. Originally I believe they were a phenolic impregnated material, they could have been changed for bronze if there has been a diff rebuild. 

Geoff

Don't  know if y9ou can get it   wherever you are, but Penrite gear oils state "Compatible with copper based components", so that is what I use.  have just rebuilt the Jet overdrive and using Penrite 75W-90 synthetic Gear oil to see how it performs.   

Jon B

I'm currently using Sta-Lube gear oil, SAE 85W90, with an API/GL-4 rating, in the transmission and rear axle of my '37.  It's fairly available in the U.S. (locate sellers with your search engine).  The container label says "non-corrosive to copper, bronze of other non-ferrous alloy bearings and bushings".

I completely drained the axle and transmission before adding this oil.

However, for most of the previous 45 years I had used many different gear oils indiscriminately, so if there's "yellow metal" in there, it's already damaged, I guess.

A side note:  just before adding this oil, my rearend and transmission had 140W gear oil (GL-4).  The (non-syncro) gears seemed to shift more smoothly using the 140W oil.  However, soon after starting to use the 140, I noticed that my engine backfired every time I kicked down the overdrive into third gear.  I speculated that the thick oil might have gotten into the solenoid and caused it to move more sluggishly.  (Thus, when the solenoid delayed the ignition during kickdown, it delayed it too long, with a resulting buildup of gasoline vapor in the exhaust.  This ignited when the solenoid finally restored the spark.)  I replaced the 140 with a lighter oil and -- voila! -- no more backfiring!  However, with the lighter oil my gears grind a lot more than with the thick stuff.