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SM420 Rebuild Kits
#1258056 Sat Mar 10 2018 12:12 AM
Joined: Sep 2007
Posts: 413
R
Shop Shark
I've been searching for the last couple of hours about rebuild kits for the SM420. I know this has been discussed frequently before. I have read Novak's site many times and they seem to be the go to source. I found a place called Transparts Warehouse that produces a kit and it is available on eBay. With a one day eBay discount I can get a kit for about $88 USD with free shipping. (I'm ordering from Canada and our dollar isn't doing well right now!) I'm not sure if it comes with instructions but I do have the links to the GM slide show and shop manuals about rebuilding the SM420. I'm well aware of 'you get what you pay for', but has anyone purchased a non Novak rebuild kit? Are the instructions from Novak different than the GM instructions (in particular, the GM instructions say to use this GM tool or that GM tool. Do the Novak instructions overcome this with information as to use readily available tools? (Novak does state on their site that common shop tools can be used.) If anyone has purchased a non Novak kit, how was the quality? If quality could be the same, approximately $100 is a lot to pay for some instructions. Also, from what I can gather, synchros are no longer available in the Novak kits. Any insight into this would be greatly appreciated. Thanks.


It's a small world, but I wouldn't want to paint it.
Re: SM420 Rebuild Kits
Rusty Shackleford #1258078 Sat Mar 10 2018 03:08 AM
Joined: Jun 2011
Posts: 3,631
E
Shop Shark
The whole job is pretty straightforward using normal shop tools like it says. Don't be scared.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: SM420 Rebuild Kits
Rusty Shackleford #1258104 Sat Mar 10 2018 05:30 AM
Joined: Jan 2013
Posts: 1,662
S
Shop Shark
I just got done rebuilding two SM420s and it was pretty straightforward. Bought the bearing kits on ebay for little over $100.
One trans went in my 53 and I am selling the other. I have a lot of sm420 build pictures if you send me your email addy. Would recommend a press and a large bearing separator, and lock rings pliers.
Also , there is a good GM SM420 repair guide that I could email you that offers step by step on disassembly and reassembly.

Last edited by sstock; Sat Mar 10 2018 05:32 AM.

1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
https://www.youtube.com/watch?v=Bli...n05i04t1aokgm4p04jiwgffwhyyih5xbk0h00410
1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration
Re: SM420 Rebuild Kits
Rusty Shackleford #1258160 Sat Mar 10 2018 06:46 PM
Joined: Apr 2010
Posts: 48
R
Wrench Fetcher
I got all of my rebuild SM420 parts from these guys.

http://www.americanpowertrainwarehouse.com/sm420-48-67-manual/

I watched the GM slideshow numerous times. I have a friend with a press so that helped. I'm no transmission guy but I didn't have any issues.


Don't pay no mind to that whirrin' sound, she uses a little oil but outsida' that she's cherry.
Re: SM420 Rebuild Kits
Rusty Shackleford #1258216 Sun Mar 11 2018 04:19 AM
Joined: Jan 2013
Posts: 1,662
S
Shop Shark
Thats right Red, pretty straight forward. Important to make sure you have .012 clearance between the second gear thrustwasher and 2nd gear. Other than that make sure everything is nice and clean and replace all the bearings and lock rings and of course worn components. This is one of the stoutest trans I have ever seen in a light truck.


1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
https://www.youtube.com/watch?v=Bli...n05i04t1aokgm4p04jiwgffwhyyih5xbk0h00410
1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration

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