The Stovebolt Site Forums The Parking Lot Big Bolts Rebuilding the Muncie SM420

Hey guys just purchased a complete transmission rebuild kit from eBay.
I am fairly savvy with this type of thing but would still like to find a good video of the procedure and hear from a few of you who have had experience with rebuilding one of these transmissions.
It will be at least a couple of weeks before I am ready first would like to get the solvent in my parts washer changed or should I just send it out for hot tanking?
Anyway your input would be appreciated Thank you

This site seems to be the place to go for info and parts, perhaps they can point you to a good manual or video.
http://www.novak-adapt.com/knowledge/sm420.htm

Denny Graham has some really good pictures of his SM420 rebuild.

Check the Links Page under "Transmission" (Amazing what you might find on this site when you venture beyond the discussion forum ... )

The link to the rock crawler site (Toyota guys) was incredibly helpful for me when I rebuilt my SM420 as was Don's downloadable SM420 rebuild manual

When one gets the cluster gear out, it is helpful for reassembly to make up a dummy shaft for it to keep the roller bearings corraled. Get a piece of the correct diameter EMT or water pipe that fits inside with the bearings in place, just short of the cluster length- wise, insert the cluster w/ bearings greased w/ dummy shaft inside, when in place, push the dummy shaft out w/ the correct shaft.

Thanks guys still like to find a video.

Well I got the rebuild kit now, contains everything but the synchronizers. Still like to find a video specifically for the SM420. I would also like to retro fit the shift cover with a reverse light switch. Has anyone here done that or maybe someone have some pictures of a later SM420 with a reverse light switch? Really just need to see where on the cover they were mounted.

Google came back with several SM420 reverse switch hits. This one shows photos of a retrofitted top cover.

http://www.kinzers.com/don/landcruiser/sm420rev_switch/

Chevrolet made an accessory back up light kit. The switch mounts externally on top of the cover with the actuation lever being attached to the gear shift lever.

They are rare and hard to find...

Mike B

Thanks Mike. The real reason I need the switch is to make the truck legal on government job sites where an audible back up alarm is required and hub bells don't meet the required sound level.As long as the switch will be there I will ad back up lights as well maybe even add lights to my trailer often have had to back through my gate at home after dark.

Hey all,
After looking for pictures/videos like the rest of you, I decided to document my SM420 rebuild with videos and posted them to You Tube. I'm good with a wrench, but I'm a newbie to a transmission rebuild. I have the shop manual and the Novak instructions. Once you get it opened up it's pretty easy to see what's going on.
Long video, full overview:
Clutch hub and clutch keys:
Main shaft overview:
Pressing on the clutch hub:
Input shaft needle bearings:

I hope these help. This site has provided lots of helpful info for me, I wanted to contribute back.
Thanks,
Greg

Greg -- THANKS!! That's excellent!

We should talk sometime -- I'm a native Nutmegger myself (born in Hartford, graduated highschool in Wallingford)

Welcome to our site and thanks for sharing what you learned!
John

HevyHauler Useing sticky grease to hold your rollers in plce especially when they are new,withanew shaft and in coolweather works good. Next look for chips on the synchronizer teeth on the2nd 3rd and 4th gears the more chips the more likely to want to jump out of gear. If the gears have ground before that hurts the teeth and the shift collars. next look at dual low and reverse when these are ground in it roughens up teeth that are expensive to chhange. Hopefully you'll havs thin shims totighten-up your end play.it can be worse on trannys that have done a lot of hard work. If you have a well worn counter shaft you can make a short shaft with your chop saw to help hold your rollers in place,then displace it with your new one. GOOD SHIFTING !!

I use a piece of EMT, just short of inside length of case, push out like fixit says.

Ed