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 ?
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 ?
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
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
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; 05/05/20211:30 PM.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
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
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
Here's some info about Gear Oil classifications. LInk You'll have to decide if GL-3 would be suitable. More info on gear oils
Last edited by klhansen; 05/06/20214:19 AM.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
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].
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
The Shop Manual calls for straight 90 weight mineral oil.
Actually, the Shop Manual has two options for the transmissions: SAE 90 Straight Mineral Oil gear lubricant OR SAE 90 "Multi-Purpose" gear lubricant. The latter being the same that the manual recommends for rear axles. The question is what "Multi-Purpose" means. There's a paragraph in the manual that attempts to describe it, but doesn't give any real specifications, other than it's designed for Hypoid gear sets (typical ring and pinion). I would probably go with GL-4 or the straight mineral oil. Although the stuff Phil linked is rated GL-1. Probably OK. It does say it's sulfur free, which is what you want for brass components.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Thanks guy for all the help. Were back on the road. For future reference. Seal and bushing kit, SKF 15054. The seal is not as deep as the original. .750 vs .453. So I use some silicon to help it, will see if it leaks. This seal and bushing are used in a number for gm trannys. Gasket kit Felpro TS 5190 Driveshaft was from a 55-57 chev car. U Joint Spicer 5-1301-X
