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Jul 21st, 2025 | | | | Joined: Jun 2005 Posts: 481 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 481 | I have a 3-speed manual transmission with an on-the-column shifter in my restored 1958 Apache 3100 pickup. Experiencing some gear grinding in 2nd and 3rd gears (after driving the truck long enough for things to warm up) and also it will occasionally jump out of 3rd gear when I am just cruising along.
Would like to know what is causing these things and see what I can see for a diagram/drawing of the transmission.
John | | | | | Joined: Apr 2005 Posts: 2,066 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 2,066 | If you have the standard Muncie SM318 3 speed transmission the problem can be one or all of the following:
2-3 speed clutch sleeve and related rings and cones.(AKA syncro drum assy).
Worn shift fork, springs, balls, and side cover components.
Worn energizer springs on 2nd and 3rd gear.
Worn bearings.
Contributing factors are bad u-joints along with sloppy shift rods and levers.
Popping out of 3rd gear is a common problem with this series transmission.
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
| | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | Add one more possibility- - - -loose trans to bellhousing bolts- - - - -I've seen it happen pretty often. Bad bearings and/or a worn 2-3 synchronizer is the most common cause.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Apr 2005 Posts: 2,066 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 2,066 | Someone else suggested a worn pilot bushing in another post on this subject. I'll add rear output shaft bushing and front driveshaft yoke to the list.
Lots of things to wear out on 60+ year old trucks.
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
| | | | | Joined: Jun 2005 Posts: 481 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 481 | All of you are loaded with good information. Thank you for your input. I am hopeful that I have found someone local that knows these old transmissions and can still work on them, especially mine. | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | They are pretty simple, get some books and do it yourself, we all have to learn. I am sure you have a neighbor that might watch over your shoulder.
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.
| | | | | Joined: Nov 2014 Posts: 70 'Bolter | | 'Bolter Joined: Nov 2014 Posts: 70 | For parts contact Southern Gear in Atlanta, they still have new shift forks, the input shaft nut and a shim with an offset in it that goes between input shaft and front bearing. The offset shim allows oil to still get to the front bearing and get a little more spline engagement of input sf/haft into the synchro drum in3rd gear. The owner Kenny is a wealth of knowledge on SM-318's since it was the first transmission they allowed him to rebuild way back in the late sixties.
ESum
| | | | | Joined: Jun 2005 Posts: 481 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 481 | Thank you ESum. More good information. | | |
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