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Transmissions and Rear Ends Three on the tree or four in the floor? Shift it all here.

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  #1  
Old April 24th, 2014, 07:26 PM
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Default Muncie SM 318 (sm318) 3 speed Transmissions All Documentation I could find

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.
Attached Files
File Type: pdf mc318.pdf (586.2 KB, Multiple views, 79 clicks)
File Type: pdf bwoperators[1].pdf (7.99 MB, Multiple views, 43 clicks)
File Type: pdf bwservice[1].pdf (5.84 MB, Multiple views, 29 clicks)
File Type: pdf bwrebuild[1].pdf (947.2 KB, Multiple views, 34 clicks)
File Type: pdf bwwiring[1].pdf (335.4 KB, Multiple views, 19 clicks)
File Type: pdf bwtips[1].pdf (803.7 KB, Multiple views, 31 clicks)
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Old July 16th, 2020, 04:32 AM
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Default Re: Muncie SM 318 (sm318) 3 speed Transmissions All Documentation I could find

Info like this when you need it is invaluable!
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Old July 16th, 2020, 08:09 PM
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Default Re: Muncie SM 318 (sm318) 3 speed Transmissions All Documentation I could find

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
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Old July 17th, 2020, 01:42 AM
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Default Re: Muncie SM 318 (sm318) 3 speed Transmissions All Documentation I could find

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