Coming back from the 45 run last night, my 420 decided that it didn't want to come out of 4th. Gutted it out and made it home in 4th only. Fortunately only had to come to a complete stop twice!

I pulled the top cover today and it shifts fine by itself but I couldn't get the forward shift collar (3-4) to move more than about a quarter inch.

Anyone have any brilliant ideas?

Maybe the 3-4 synchro hub keys took a dump, but your won't know util you take it apart. NOS parts are available from Tourist Auto Transmissions in SLT, Utah.

yup , hub keys or the big spring that holds em. Kick the handle harder from the back seat. :p

yup , hub keys or the big spring that holds em. Kick the handle harder from the back seat. :p

I looked at those little keys as a possible culprit. I gave the lever about as much abuse as I felt anything could take without cusing further damage, one hand, two hands, one hand with some serious impact!!!!!!!

Are the keys a known problem area?

Where were you, Mellonhead?

sucking on mama's boob. I already said she would not give my balls back.
it just was not in the cards . Pismo for a week is tho and to Georg , the condo is crashable till Fri night then I'll have to kick you out on the beach for the weekend .

Kent,

It sounds like either a key or syncro broke. I have seen a syncro split in half, so that the front part was seperated from the back.

Bummer, but atleast you made it home.

-Dustin

I had one split and expand out ever so slightly. Took forever looking in the dam case to figure it out, Finally so the crack and relized thats why it wouldn't let the chollar slip over. Pain in the ass. I bought a different tranny from the junkyard and threw it in. :laughing:

The keys and springs are still available from County Gear in Spring Valley. There are two different styles of keys and they know if you describe them when ordering.
Another possibility is the main shaft rear bearing. If it becomes sloppy or loose in the bearing bore the whole main shaft will move rearward. Every part on the main shaft becomes sloppy and cocks over resulting in locked up gears.

Another possibility is the main shaft rear bearing. If it becomes sloppy or loose in the bearing bore the whole main shaft will move rearward. Every part on the main shaft becomes sloppy and cocks over resulting in locked up gears.

I had a similar thing happen with the bottom shaft, when I forgot to install the retainer clip on the rear bottom shaft bearing- and it allowed the shaft to move forward, binding the gears. When that happened, it was near impossible to shift in ALL gears. But, if the rig was off (nothing spinning) I could get it in and out of gear.

-Dustin

You might check with http://www.novak-adapt.com. They carry master rebuild kits for SM420's that include pretty much everything. No affiliation, just a satisfied customer.

Well I got it out of gear by depressing all three keys at once and pushing back on the 3-4 collar w/4 hands, thanks to input from Rich Sturgeon. It all works good now, but what would let it over shift into fourth?

Well I got it out of gear by depressing all three keys at once and pushing back on the 3-4 collar w/4 hands, thanks to input from Rich Sturgeon. It all works good now, but what would let it over shift into fourth?

Broken snap ring or bad bearing. Check the end play in the shafts.

Broken snap ring or bad bearing. Check the end play in the shafts.

Any specs for end play, Doug?

Any specs for end play, Doug?
Paul Nasvik (Nasvik on the PBB) rebuilt this 420, I bought it and had similiar problems.
Wasn't Paul's fault, it was an engineering detail left out from Novak's kit for the Dana 300, missing cir-clip from main shaft. Regardless, Nasvik made a really nice write up on the rebuild on his website, found in his PBB profile.
Here's a file page of his, at the bottom is a scanned rebuild manual. Save, copy and print. I can't remember if it had end play specs, if not, Call Novak and ask Dewie. Dewie is the SM420 guru, he even has a Proffessor at the shop making syncros for first gear in his off-time.
Here's the link to Nasvik's file page;
http://www.jeepshots.com/shots/projects/sm420/

Or go here;
Jeepshots (http://www.jeepshots.com)
and click on tech.

Wow, thanks for the link Doug...here I am putting my SM420 back together after a couple of months and just wanted to double check some stuff to make 100% sure I was doing it right. A quick search of SM420 rebuild on Pirate brought this thread up :)

Broken snap ring or bad bearing. Check the end play in the shafts.

X2 on the snap ring or shaft play or else the key retainer spring broke. If you take the PTO cover off, you may find the culprit stick on the magnet. Otherwise take it apart and find out.

Novak is mighty proud of their rebuild kits. I got my complete master kit for $75 less from my local transmission shop.