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Does anyone have any recommendations for the best oil to put into a 28 worm drive rear end? I am getting ready to completely rebuild my hi speed worm drive and want to make sure I put correct oil for the bronze bevel gear. I have heard pros and cons on the 600w oil available today. Any help would be great.
Thanks

rustya1928 wrote: ↑

June 16th, 2021, 4:49 pm

Does anyone have any recommendations for the best oil to put into a 28 worm drive rear end? I am getting ready to completely rebuild my hi speed worm drive and want to make sure I put correct oil for the bronze bevel gear. I have heard pros and cons on the 600w oil available today. Any help would be great.
Thanks

Refer to the article in the 2017 Double A'er "Proper Gear Lube - Model AA 28-29 Worm Gear Differentials"

SPO 288 - Lubriplate SPO Series is one of four recommended for the yellow metal worm gears.

I use 600 w steam oil. Whatever you do DO NOT USE any oil with ep additives, this will destroy your bronze worm gear.

1wonton wrote: ↑

June 20th, 2021, 6:50 am

I use 600 w steam oil. Whatever you do DO NOT USE any oil with ep additives, this will destroy your bronze worm gear.

Yes, the article noted above talks about EP additives:

"You can see in the photo the difference between 2 bronze gears removed from AA differentials. The lower one was run in the correct lube and the upper one apparently was run in lube that deteriorated it; most likely the sulfur/phosphorous EP (extreme pressure) additives in GL-5. Note the (1) weakened teeth and (2) cracked mounting ears on the inside of the upper gear. Also note the (3) smooth tooth contour of the teeth on the lower gear compared to the (4) jagged, erratic and sharp contours of the upper teeth. Although it is hard to see in the picture, note the (5) buildup of the EP additives flaking where the teeth don't contact it and wear it down. I am told that these additives also leach the lead out of this bronze, weakening it. All the cracked mounting ears seem to confirm this. The housing for the upper gear was filled with bronze nodules resembling “popcorn” scraped off a ceiling to the point that the drain plug would hardly drain. These bronze chunks also got into the bearings and even plugged the lube channel to the rear bearings for the worm gear."

"I frequently hear, if I only buy my gear lube from Model A parts suppliers it is good for our AA’s, right? Maybe. If it is formulated with the GL-5 extreme pressure (EP) additives, it will be excellent for a hypoid gear differential, but these same EP additives will kill your bronze gear."