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Purdy Swoft · 12-16-2012, 05:10 PM

It was recommended to use straight STP as a gear lube in one of the model A magazines several years ago. I took it for gospel and put it in my 31 tudor. STP seemed to work fine at first but after several years I noticed that our sedan didn't shift nearly as well as our other model A's. I decided to replace the STP with the 600W offered by Snyders and see if it would make any difference. I removed both plugs from the transmission and after an hour or more, not one drop of the STP had drained out. I ended up using the heat gun on the transmission for 30 minutes or more before it liqufied enough to mostly drain out. After pouring in the Snyders 600W The gears shifted the way that they should.

STP is mostly a viscosity booster (thickener) . If used straight as a gear lube, after a few years it thickens. It has been said that some model A vendors make their own gear lube by mixing 140 weight and STP and call it 600W . I have used the mix lube with no problems but had problems with straight STP after a period of time.

Some make a big deal about gear lube and buy large quanities of certain brands of gear lube that they believe is closest to what Ford used in the day. I agree with Timothy Kelly, 600W doesn't mean 600 weight but was the part number. The actual weight of the gear oil that Ford used was closer to 250 weight. I understand that Snyders Gear lube is 250 weight and that is what I now use.

I've owned model A's since the spring of 1960 . As a teenager with a part time job after school, I didn't have a lot of money to pay shipping on some unheard of gear lube. I used 140-90 weight gear lube that I could get locally. I had good results and never a problem. I didn't start using the model A vendor 600W untill sometime after 1978 and never felt a difference.

Just to add a note. When adding lube to the transmission or backend , stop pouring at about an inch below the level of the fill plug. This practice will help keep gear lube off the brake lining and be less likely to leak.

12-16-2012, 05:10 PM	#23
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: Transmision and Rear End Fluid question. It was recommended to use straight STP as a gear lube in one of the model A magazines several years ago. I took it for gospel and put it in my 31 tudor. STP seemed to work fine at first but after several years I noticed that our sedan didn't shift nearly as well as our other model A's. I decided to replace the STP with the 600W offered by Snyders and see if it would make any difference. I removed both plugs from the transmission and after an hour or more, not one drop of the STP had drained out. I ended up using the heat gun on the transmission for 30 minutes or more before it liqufied enough to mostly drain out. After pouring in the Snyders 600W The gears shifted the way that they should. STP is mostly a viscosity booster (thickener) . If used straight as a gear lube, after a few years it thickens. It has been said that some model A vendors make their own gear lube by mixing 140 weight and STP and call it 600W . I have used the mix lube with no problems but had problems with straight STP after a period of time. Some make a big deal about gear lube and buy large quanities of certain brands of gear lube that they believe is closest to what Ford used in the day. I agree with Timothy Kelly, 600W doesn't mean 600 weight but was the part number. The actual weight of the gear oil that Ford used was closer to 250 weight. I understand that Snyders Gear lube is 250 weight and that is what I now use. I've owned model A's since the spring of 1960 . As a teenager with a part time job after school, I didn't have a lot of money to pay shipping on some unheard of gear lube. I used 140-90 weight gear lube that I could get locally. I had good results and never a problem. I didn't start using the model A vendor 600W untill sometime after 1978 and never felt a difference. Just to add a note. When adding lube to the transmission or backend , stop pouring at about an inch below the level of the fill plug. This practice will help keep gear lube off the brake lining and be less likely to leak.