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SM318 tail shaft removal and install, seal and bushing
#1408611 Tue May 04 2021 04:16 PM
Joined: Nov 2019
Posts: 10
S
'Bolter
I have 57 GMC 9300, 235, SM318 three speed. Canadian model. The seal and bushing are toast on the tail shaft. Can anyone tell me the part numbers? I expect I'll get the bushing replaced at a shop because a don't have the proper puller.
I pulled the tail shaft off. When putting it back on, is it as simple as it was to remove it. Will everything inside the tranny line back up. Of do I need to pull the side cover off ?

Last edited by Sparky77; Tue May 11 2021 11:27 PM.

57 GMC 9300, 235, MS318, S45
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408632 Tue May 04 2021 06:50 PM
Joined: Nov 2019
Posts: 10
S
'Bolter
When I pulled the tail piece off, washer "A" in the pic fell off. I believe it goes here. However, there appears to be a polished area in front of washer "B". If this section of the shaft rides in or on something inside the tranny, it has a smaller OD than washer "A" does. So how does wash "A" get passed the smaller section when the tail shaft is installed ?

Attached Files
Tranny shaft.JPG (183.15 KB, 93 downloads)

57 GMC 9300, 235, MS318, S45
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408649 Tue May 04 2021 09:27 PM
Joined: Apr 2005
Posts: 1,865
R
'Bolter
You will need to disassemble the transmission to get it back together. You now have all the needle bearings in the bottom of the case.
To replace the rear bushing, expand the snap ring behind second gear and drive the mainshaft out. You can now remove the seal and drive the bushing out with a punch or chisel at the slot in the tail housing.
The seal is common to just about all Chevy manual transmissions, PG and TH350 at any parts store.
The seal number from my source, Anahiem Gear, in Anaheim CA is 8850, the bushing is 8008.
I don't know if those part numbers will help you in your area however.

To reassemble: Remove the side cover & clutch gear. There are two rows of needle bearings inside of the clutch gear.
Using grease to keep the needle bearings in place, install the larger needles in the bottom position, then install washer A
Next install washer B with the shinny side out and install the smaller needle bearings up against the washer

At this point you may also need a gasket set. It will be necessary to line up the syncro with the main shaft and the clutch gear when re-assembling the components.

Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408665 Tue May 04 2021 11:13 PM
Joined: Nov 2019
Posts: 10
S
'Bolter
Excellent, thanks Fred.


57 GMC 9300, 235, MS318, S45
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408677 Wed May 05 2021 12:07 AM
Joined: Nov 2019
Posts: 10
S
'Bolter
Any words of wisdom about taking the side cover over off that will make removal/reinstall go better. ?
Gear position ?
Parts alignment ?
Springs to catch before they fly across the shop


57 GMC 9300, 235, MS318, S45
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408716 Wed May 05 2021 01:28 PM
Joined: Feb 2019
Posts: 1,976
P
AD Addict
There are some excellent videos on YouTube, that show disassembling and reassembly that I used rebuilding my tranny. Do a search on “SM318” and you will find several.

Last edited by Phak1; Wed May 05 2021 01:30 PM.

Phil

1952 Chevrolet 3100
Project Journals
‘59 235 & hydraulic lifters
“Three on the Tree” & 4:11 torque tube
12v w/ Alternator
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408729 Wed May 05 2021 03:33 PM
Joined: Apr 2005
Posts: 1,865
R
'Bolter
Put the levers in the neutral position. Nothing is going to fall or spring out. Check for wear on the shift forks. The 2-3 fork is a common wear part. Also, it's generally a good idea to have a shop manual when doing this type of work. The SM318 transmission was used in 55-66 Chevy cars & trucks. You don't necessarily need a GMC manual.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408807 Thu May 06 2021 02:47 AM
Joined: Nov 2019
Posts: 10
S
'Bolter
Thanks guys. Got the old seal and bushing out. Now to see if I can find all the needle bearings.
While I got your attention, I've read a bunch of posts about GL4 vs GL5 tranny fluid.. GL4 good, GL5 bad.
What about GL3 ?? Local supplier has Pennzoil Synchromesh GL3. An oil type I haven't seen any posts about.
GM part 12345349 or 12345577, spec 9985648

Last edited by Sparky77; Thu May 06 2021 02:47 AM.

57 GMC 9300, 235, MS318, S45
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408813 Thu May 06 2021 03:58 AM
Joined: May 2015
Posts: 4,039
Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums
Here's some info about Gear Oil classifications.
LInk [recondoil.com]
You'll have to decide if GL-3 would be suitable.
More info on gear oils [widman.biz]

Last edited by klhansen; Thu May 06 2021 04:19 AM.

Kevin
First car '29 Ford Special Coupe
#2 - '29 Ford pickup restored from the ground up.
Newest Project - 51 Chevy 3100 work truck. Photos [flickr.com]
Busting rust since the mid-60's
Re: SM318 trail shaft removal and install, seal and bushing
Sparky77 #1408829 Thu May 06 2021 11:51 AM
Joined: Feb 2019
Posts: 1,976
P
AD Addict
The SM318 was also used in earlier models as in my ‘52 3100. The Shop Manual calls for straight 90 weight mineral oil. Tractor Supply carries “ Traveller, Ford Tractor All Mineral 90 Transmission Fluid in 2 gal. containers, which meet all specs. Here is a [LINK] [tractorsupply.com].

Attached Files

Phil

1952 Chevrolet 3100
Project Journals
‘59 235 & hydraulic lifters
“Three on the Tree” & 4:11 torque tube
12v w/ Alternator
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