The Stovebolt Site Forums The Parking Lot '60-'66 Trucks 65 gmc transmission

i have a 1965 gmc with 230engine, 3 speed on column. the transmission in my truck is not synchronized. did it come this way? i would like to change it out for one that is. what models will fit? thanks rar

Yeah, it came that way. Probably the muncie 318. I have the same transmission. Sometimes called the peanut transmission because of its size. The mc318 came on an assortment of engines and will bolt to most any chevy motor. I have mine bolted to a 396

Like jon1963 said, it's probably the SM318. If it has 4 side cover bolts, that's what it is. The most common replacement would be the Saginaw 3 speed, used from '66 up. It uses the same input shaft, but the output shaft is a fine spline like a TH350 or 700R4 automatic. It is also a little longer than the SM318, so the driveshaft would have to be shortened or replaced. Also, the front bearing retainer on '68 up truck transmissions is larger, so to use one from a '68 or newer truck you could either use a bearing retainer from a car Saginaw or just have the truck retainer turned down to fit your bell housing. You could also use a '68-'72 truck bell housing. A car Saginaw would fit your bell housing, you would just have to use longer bolts with nuts for the 2 bottom bolts, the 2 lower bolt holes on a car trans are not threaded. Hope that helps.

After re-reading that last post, just let me point out that the Saginaw was not the ONLY 3 speed used from '66 up, but it was one of the transmissions used thereafter. The SM318 was also still avaiable through '67. Sorry for any confusion.

It's only non syncro in 1st & reverse. 2-3 have syncro's.

so does that saginaw 3 speed have a synchromesh 1st? i have a three speed in the 62 and it can sometimes get dodgy driving in town and not being able to drop into 1st until i hit a near full stop. wanna keep the column shift but a synchro first would be pretty sweet!

appreciate the info. i have a 66 chevy parts truck that has a 3 speed in it. i knew it was different looking but did not know if it was scyronized or not. i also do not know if its any good. be worth checking out though. thanks rar

Hopefully you have a Saginaw in that '66. The Saginaw has a 7 bolt side cover. There was also an optional heavy-duty Warner 3 speed, used from '63-'67 and maybe more years, not sure. It too had a non-syncro 1st gear like the SM318, but it should be a top-loader with a 9 bolt cover.

ok so this is might be a dumb question,, but what is the differance between a non syncro and fully syncro transmission as far as for daily diving and the benifits of the later fully syncro trans???

With the non-syncro trans, if you don't come to a near complete stop it will grind going back to 1st gear. Some will even grind from neutral to 1st at a dead stop if you try to put it in too quickly after pressing the clutch. Someone who is used to driving one can do so without ever grinding the gears, some people even prefer the "crisp" feel of a non-syncro transmission. Like anything else, it's pretty much personal preference. The syncronizer in itself does not make the transmisson any stronger, just easier to drive.

thanks for the info TruckNut. i bought a non sync 3sp od to open drive my 49' burb and was starting to regret my decision but since i have never had a colum shift i should be ok.

If you learn how to double clutch you can put it in 1st. while you are still moveing. Put in the clutch & shift to neutral. Let out the clutch & rev the engine to the speed it will be going when it is in gear. Shift to first & let out the clutch. When you do it a few times you will catch on & it is real cool & will impress your passenger. When you are sitting still in neutral & want to shift to 1st. Put in the clutch & shift partway into 3rd gear & then go to 1st. The 3rd gear syncro. will stop the gears & clutch disc & let you shift to first without grinding.

I'll have to try that 3rd to 1st move. I've been driving a non-synchro for so long that I forgot how to grind the gears. I just know when I can or can't put it in a gear.

awesome. i'm pretty excited to give that a shot.

thanks for the tip.... i dont wanna be looking like a fool grinding the gears when i take of

i tried that 3rd to first shift today, it sounded pretty crunchy! should i worry about damaging the gears at all? if not it sounds pretty tough!

You shouldn't be grinding those gears. The teeth are probably half worn off by now anyhow. If you put it in 2 or 3 & go right to first it should not grind unless the clutch is draging. Sometimes heavy gear lube can help. Like 85/140.

I had the Saginaw 3-speed installed in my '65-230...had to shorten the driveshaft. The shifter linkage had to be modified for the 3-on-a-tree configuration.

Works great now...

MDL

what kind of modifications is needed on the shifter to replace the sm318 with the saginaw?

Hey PcolaMike

How about a couple pictures, would like to put the later model trans in my truck and keep the colunm shifter.

Thanks,
Tommy

Hey PcolaMike

How about a couple pictures, would like to put the later model trans in my truck and keep the colunm shifter.

Thanks,
Tommy

Just as a point of reference, how much hp will one of the 3 speeds in a 66 handle. Mine has a 250 6 right now and i am getting ready to drop in a 350, could I leave the 3 spd in it ? or would it not be able to handle the torque ....??

the 3 speeds came behind the 350's and they also use saginaw's in some circle track race cars. I am sure it will hold up as long as you dont abuse it much.