Muncie SM 318 (sm318) 3 speed Transmissions All Documentation I could find

[FetchMeAPepsi]

Sharing all the info I have on the Muncie SM318 trannys. Rebuild kits are easy to find on Ebay or you can buy the pieces part by part at your local store and make your own gaskets. See me rebuild mine starting here. Hijinks included.


The OD on some of these 318s is supposedly a big difference in performance for our trucks, allowing them to get up to 68mph at top end and get much better gas mileage. I might be falling into one here shortly. You have to have a special drive shaft made or have yours shortened to make it work, but then you're good to go.
They work by kinda putting a second transmission behind your first one. The second tranny is run by an electric solenoid that pushes it into gear when you want to up-shift. You get up to 50 or so with your normal tranny, hit a button, and it shifts into "fourth" gear and you can continue on.

Since its two different trannys you actually have six gears now, but mainly theyre used for a 4th gear. Here's a wiring diagram I found for the OD unit







You can buy a repo solenoid here:
http://www.fifthaveinternetgarage.co...counter_3.html



Attached is scans of the SM318 rebuild manual, OD operator's manual, OD service manual, OD rebuild manual,OD wiring document, and OD tips and tricks.

[Tony]

Info like this when you need it is invaluable!

[Quigley]

The overdrive version is a SM319. It uses a Borg Warner R10 overdrive unit. The ones I have used are the same length as th 318 and will bolt right in with no modification to the driveshaft. I used the side plate with the original shifting arms off the 318 and kept my column shifter without any mods. Dave

[LEWISMATKIN]

the sm319 is the long mainshaft version. the sm 318 has a shorter mainshaft.

[Shsh]

Originally Posted by Quigley

The overdrive version is a SM319. It uses a Borg Warner R10 overdrive unit. The ones I have used are the same length as th 318 and will bolt right in with no modification to the driveshaft. I used the side plate with the original shifting arms off the 318 and kept my column shifter without any mods. Dave

Is this synchronized?

[Quigley]

Originally Posted by Shsh

Is this synchronized?

No it’s not.

[Truckee]

I’m about to install a SM318 in my 1965 1000 series truck. There’s no bell housing dust cover on the truck. Is it necessary to have one and, if so, where in the world can I find one? Thanks, Tim

[FetchMeAPepsi]

Originally Posted by Truckee

I’m about to install a SM318 in my 1965 1000 series truck. There’s no bell housing dust cover on the truck. Is it necessary to have one and, if so, where in the world can I find one? Thanks, Tim

It's not 100% necessary, but it is nice to have. Thing is, they're like frog teeth. Lots of shops took 'em off and tossed 'em when they worked on the clutch out of laziness. Lots were shorn off when people hit bumps driving in the bush. And a bunch were probably just rusted out. They take a lot of damage.
If you can find one, grab it with both hands. If not, just slide your sm318 up in there and drive on, brother! Just glance up there from time to time and make sure the neighbor's cat isn't up there!

[AZKen]

Originally Posted by Quigley

No it’s not.

How do you shift it if it's not synchromeshed in 2nd and 3rd???? Are you saying it's a crash box? NOVAK says "SM" stands for Synchromesh.
My understanding is the 319 is basically the same as the 318 with OD adapted? It's not fully synchro.

[LEWISMATKIN]

The sm-318 & sm-319 are the same transmission except for the length of the mainshaft(tailshaft). Neither are syncronized in 1st gear. both are syncronized in 2nd & 3rd. the internals are the same.