The Stovebolt Site Forums The Parking Lot Big Bolts Brownie questions

I have a later Brown Lipe/Spicer and have overhauled it recently. It always leaked oil despite the factory no-seal setup so I fabricated seal holders, went through the seal catalogs and found appropriate seals and bought speedie sleeves to cover the yokes. It leaks a great deal less oil now. I think turning them fast on the highway churns up more oil than the original system can handle. My input shaft turns ~2800 RPM and the output around 3300 RPM in overdrive at 60 MPH. Originally, I think they turned a max of about 2100RPM on the input. Also do not overfill them. Mine is quieter and leaks less with the oil level about 1 inch below the fill hole according to my calibrated finger. Mine says to run 50Wt mineral oil, not 90wt gear oil. In winter I run 30wt and it's much easier to shift. We are well below freezing most of the winter here.

The SM420 is tough as nails and should not need much attention unless it's been abused or run out of oil. But by now some of them do have a lot of miles on them. Also check to see that the pilot bearing hole in the crank is concentric with the big mounting hole in the bell housing. You can do that with a magnetic stand and a dial indicator. I have read that some bell housings were more than 0.010 off center from the factory. At one time there were sold offset dowel pins to correct this. There is a Jeep outfit in Utah that still sells them I think. Being offset will shorten the life of the input bearing and the pocket bearing. The pocket bearing can be a particular problem because the needles don't have an outer race and run right on the inside of the main drive gear. When that surface goes gunnyshack you'll be looking for a new main drive gear.