Where to buy a rebuilt SM420

[JONNYFJ]

So I really need a new tranny I want to upgrade to a NV4500 but don't want to fork out the extra cash to mod my drive line, so does anybody know who sells rebuilt SM420s

 

[Poser]

N O V A K <---- this is a link

 

[JONNYFJ]

Sweet thanks

 

[Josie'sLandCruiser]

Hi All:

Do a search here on MUD, I remember someone ("Tigerstripe40" ?) mentioning NOS ("new old stock") US Govt. SM420s for sale as surplus from some shop.

Novak is a great source of info on older North American trannys and t-cases.

Good luck!

Alan

 

[JONNYFJ]

Only problem with N.O.S SM420 is that they are normally shipped without the top shifter plate. I all ready ran into that problem with antelope valley equipment. The N.O.S SM420s they have come from the Vietnam era Gama Goats, and if you know anything about the military, we are a bunch of rocks. So the Government had the top shifter changed out to a electronic (kinda like an automatic) and now you have a hell of a time finding one that fits with your top cover. They are really cheap though I bought mine 4 285.00, but is just a large paper weight for me. I think I am going to buy one from Novak they are complete thats what I need

 

[Alz Toy]

Another Place

Also check out " Herm the Overdrive Guy ". He has parts for them, as well as rebuilds. HTH, Al

 

[Sputnik40]

I bought mine from someone on here or the old LCML - and he indicated it had been totally rebuilt by an outfit out west called MIT? Might be worth a search if you wanted to price shop...

 

[kellyo]

JohnnyFJ, can't you use the shifter from another trashed 420 in place of the gamma goat top plate. Beats using it as a paper weight.

 

[JONNYFJ]

JohnnyFJ, can't you use the shifter from another trashed 420 in place of the gamma goat top plate. Beats using it as a paper weight.

I tried using my old plate and it no longer fits, I called a friend who builds trannys he told me that they machined the case for the Gama Goats. So its no long the same bolt pattern, also first gear is kinda different. The guy over at AA told me only the early models of the SM420s top plates would work I wish I new more about them because this is a hear say.

 

[brew8]

I have a gamma goat tranny, I used an old top plate from the 50's it fit fine but the tranny stuck in 3rd gear, I found a top plate from a late model SM 420 maybe the late 60's and it fit and works fine, no sweat, just spend some time at the pick and pull and you will find what you need, keep your three speed shifter it works great and is not too tall. There is an outfit in Salt Lake City Utah that sells NOS tranny's as well just do a search under SM 420, I bought mine from Saturn Surplus, cheers, Larry


Here is one other Tourist Auto and Truck, SLC Utah, 801-364-5743

 

[JONNYFJ]

So here is what I got after a lunch break of phone calls. The Gamma Goat SM420 will work with the 50-late 60's model GM SM420 top plates. ? is how do I tell if mine is 50s to late 60s. Where would I look and what would I be looking for

 

[brew8]

Look for the ribs on the case the later models have a seal instead of a slinger but you have to take the nose off to tell that, there are also some info in the tech links on the casting numbers that you can use to identify them, Larry

 

[Pin_Head]

? is how do I tell if mine is 50s to late 60s. Where would I look and what would I be looking for

Here is a link to identification of different models. I don't think the date range is correct for the mid range split when they used identical 3-4 synchro rings as my '61 has identical rings and a casting number of 38XXXX
The GM Muncie SM420 Transmission - Novak Conversions

The date code is also cast into the case:

sm420

There is a letter for the month, followed by two digits for the day and two digits for the year.

 

[JONNYFJ]

Nice thanks. Will finally be able to get the 40 back on the road.

 

[brew8]

I read an article in an old (1982) issue of an off road magazine. They had this same problem but they said there were 2 series of shift forks for the 3rd to 4th gears, that there was 3/16 th of an inch difference between them, the split date was 1961 for the later fork, they also suggested you can just change the fork, so you likely could change the 3-4 gear shifter fork out of the gamma goat tranny and all's good, Larry

 

[CruzrDave]

Just saw this.
We have 4-5 SM420's instock. We also do rebuilds on the SM420 and 465 among other. If you have had no luck give us a call 559-25-CRAWL

Dave from Marlin's

 

[woooody]

Novak is expensive.

Marlin's is $550 -- I had heard that old UC Govt ones were $450, but Antelope wants $650

 

[peesalot]

Why not just fix yours ? there is a guy here in SR that could knock thru it fast. He gots him some big box of 420 parts too.