sm420 stuck in gear

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Didn't check. Took out the calipers and measured everything before I bolted it on. All was an exact mirror image. I'll check tonight and post up. I did contact novak and the tech guys said that any age top cover should work with the tranny but the top cover pieces are not interchangable due to the difference between metal and plastic shifter plates.

The only thing that may not work due to the metal shifter interlock plate is the shifter. I won't know for certain that it will stay in reverse until I seal it back up and throw oil into it. Thursday after work will be the soonest.
 
Not staying in reverse doesn't sound right. Are you sure that the reverse pawl is engaged properly with the top cover? Better to check now while it is easy. The reverse gear doesn't have a detent to hold it in position, so I put some grease on the shaft to hold it in position while I put the cover on.
 
Pin_Head said:
Not staying in reverse doesn't sound right. Are you sure that the reverse pawl is engaged properly with the top cover? Better to check now while it is easy. The reverse gear doesn't have a detent to hold it in position, so I put some grease on the shaft to hold it in position while I put the cover on.
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Thanks for the info. I'll pull the cover off and check. (might even post a pic so you can see if it is in the right position) Is the reverse pawl circled in the picture?

Also for Poser, The last number is almost unreadable (from rust and cleaning) But it looks like A 11 6 (3 or 1) so top cover is Jan 11 1961 or 1963.

I talked to Marlin tonight. He said there are two types of top covers and he never has seen a plastic shifter indent before. He believed the difference in the covers is for a long or short shifter throw. The really early are long throw and more receint are short.

Old cover Nov. 23, 1962
SM420 1964-67
new cover Jan. 11 1961 or 63. Difference is metal shifter indent.
topcover1.webp
 
Yes that is the reverse pawl. The gear likes to slide while you are trying to get the top cover on properly, so stick it in place with a dab of wheel bearing grease on the shaft. It should shift normally when everything is right.
 
I have a 64 c20 with a sm420 tranny...the transmission would only shift 1 and 2.... 3rd and 4th wouldn't shift ...I pulled the cover to see if anything was wrong but now it won't go into neutral... Before it would..I believe when I pulled out the cover the it was in 1st gear ...I tried several times and the shifter moves 1st 2nd and also neutral but its stuck in gear..HELP.
 
erick64 said:
I have a 64 c20 with a sm420 tranny...the transmission would only shift 1 and 2.... 3rd and 4th wouldn't shift ...I pulled the cover to see if anything was wrong but now it won't go into neutral... Before it would..I believe when I pulled out the cover the it was in 1st gear ...I tried several times and the shifter moves 1st 2nd and also neutral but its stuck in gear..HELP.
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That is strange. Without being able to see it, I would make sure that the top cover can shift properly when it is off. If it can, then make sure that the top cover and all of the gears are in N and carefully reinstall the top cover and try again. Put some grease on the reverse gear shaft to prevent it from sliding when you are trying to reinstall the cover. If you have a two wheel drive truck, you don't have a transfer case, so you will need to jack up a rear wheel and spin the tire to check if the tranny is in neutral.
 
The tranny is in gear .. Tried pushing the truck when its on neutral (according to the shifter) and it won't move. I removed the top cover and I could only shift 1-2 the rest is stuck.
 
Pin_Head said:
Just remove the shift lever (Press down on the retaining ring and turn) and put the shifter rails back in N (where they are all lined up in a row) by prying them with a big screwdriver. Reinstall the lever. It is about a 5 minute job.
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Hello,

You wrote this over 20 years ago and last week it helped me to figure out an issue that had stumped me for months. Thank you!
 
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