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Jan 2, 2005
Tulsa, OK
I recently got an SM420 for next to nothing. When I opened it, I found that it had some water in it. The gears have a little surface rust but I think everything can be cleaned up after I take it all apart.

Am I wasting my time? Or can I clean everything - get a kit with bearings, gaskets, and synchros - put it back together and it will work a long time?

Thanks for the help.
Clean it up and run it.

Good trans.

Good luck!


Not really alot of rust. The shafts in the top housing seem to be the worst. I think I will take it apart clean it and see where I am. I will keep you in mind if the gears look too bad. How far is Goddard from Tulsa?
I think the main concern would be rust of the contact portion of the teeth and even then it would probly need to be really pitted to be an issue. The SM420 is a stout unit.

Just west of Wichita. I'm gonna trying to get to a GCC meeting in Tulsa. Also gonna try to wheel Disney (Grand Lake) a few more times this year.

One suggestion on tearing into the tranny; Print off Charlies write-up out of the tech section (up top) and read it a few times then keep it with you during the built. He's da man!!!
Novak came thru with the rebuild kit for my 465 with step by step instructions so far so good but u can also buy just the bearings if your gears are ok
RUSH55 said:
Don't forget to just go ahead and get new synchros, that is, as long as the teeth on the idler shaft aren't too far gone.


At the minimum, I would replace the 3-4 synchro rings. They are about $15 each. I got a master rebuild kit with synchros and all new Timken bearings and gaskets at my local tranny shop for $75 less than Novak.
Thanks for all the info. I don't think the tranny is that bad. I have decided to go ahead and get a rebuild kit with synchros and do it right. But I blew the engine in the 60 recently so I am concentrating on getting the old 75 Monte Carlo running again and ready for sale. Anyone need a 75 Monte Carlo???? The SM420 will get done - just a little later.

I am printing out Charlie's tech notes. I got the SM420 manual from the tech section and it seems to help so far in the disassembly. Thanks for the tip 66fj40x2. Hope you make it to a GCC meeting. I try and make all the ones in Tulsa but can never seem to get to the OKC ones. Maybe one day...

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