Surface rust on internal tranny gears???

[Benjitis1]

Just picked up a couple of sm420 trannies. The oil had been drained from one tranny and there is surface rust on most of the gears inside the case. Anyone experience this? Clean them with something? Or run it

Also, this tranny has the rubber seal on the input shaft bearing retainer. If the gears are junk, is it possible to use the sealed bearing retainer on the older sm420 tranny that doesnt have the seal?

 

[cruiser_guy]

Surface rust is not a big deal depending on how deep it might be. As for the seal, you need some smooth area for the seal to run on or you'll tear it up in no time so if you use the retainer on the other tranny make sure there is a machined area for the seal to ride on.

 

[Pin_Head]

As long as the rust and pitting doesn't weaken the gear or extend through the case hardening (.010) it should be OK. The input shaft is different on the ones without the seal, so you can't just swap retainers.

 

[Benjitis1]

Good to know that i cant swap seals. Any idea how to get rid of the rust? Or should i just run it? Seems like if the tranny was filled with fluid and ran, the rust couldnt get worse.

 

[zebrabeefj40]

I have a non-USA 4-sp in one of my 40's. I bought it and had it in storage until I was ready to install it. While in storage the storage area flooded and filled the trans with 8" of water which rusted the internals. I bought a rebuild kit and tore the trans apart. Used Scotchbrite pads to remove the rust from the gears and shafts as needed. Reassembled and installed in the Cruiser. I DD that Cruiser for at least 30K miles since then with no issues from the trans.

In short, get a rebuild kit for it, go through and clean it up then run it. Novak has good kits for SM420's and 465's.