Transmission info for my 6 cyl. (250)

[GreenBay1921]

I'm working on a '68 C10 with a inline 6 (250) with manual transmission. The truck has been sitting for 23 years. It is making sort of a scrubbing noise, but if I pushed the clutch in it would quiet down. It also made sort of a roaring noise in 2nd gear. I checked the tranny dope & it looked like junk, so I pulled the bottom plug to drain it & 8-10 oz of water came out. I filled it back up with fresh gear oil, & it quieted down some. I pulled the tranny tonight. When I pulled the driveshaft a little more water poured out. The gear oil looks like crap still, so my question is: should I flush out the tranny & fill it up with clean oil, or should I just have the tranny rebuilt? Also, does anyone know what model tranny I have. I'd like to do some online research, if possible. I have this crazy thought that I might be able to rebuild it myself, but I may just take it to a friend that rebuild them instead. Clutch looks good, but the pressure plate & flywheel has some pitting, so I'm going to take care of that as well.

[Greasey Harley]

it's hard to say with a 47 year old truck, most of them came with either Muncie 3-speeds, or SM465 4-speeds.
I have seen everything from Saginaw 4 speeds, to Saginaw 3 speed, to Muncie 4 speed, and a whole slew of other transmissions stuffed in these trucks.
I guess what I'm trying to say is, we're going to need more information.

If it was my truck, I would be inclined to flush it out and refill it with fresh oil. Then run it for a few miles and check it, before I did anything else.

[GreenBay1921]

Looks like there's still water in there. The tranny is a 3 speed. Here's a # off of it. Where else should I look to help figure out the model? Thanks.

[Greasey Harley]

Looks like a Muncie 3 speed.
Building a manual gearbox can be a bit tricky, but you couldn't ask for a simpler one to start with.

[jakewalter]

The (scrubbing) noise might be the throw out bearing.

[hamjet]

The noise in 2nd gear can be the gears are rusted and pitted from sitting in H2O for years. Boy, the shift forks look too close together in that pic to be either a muncie or saginaw

[Greasey Harley]

Originally Posted by hamjet

... Boy, the shift forks look too close together in that pic to be either a muncie or saginaw

Looks just like a Muncie mc318, to me.

[GreenBay1921]

I found this # on the case: 3830210. If I Google it, it shows a Muncie sm 318. I talked to a buddy of mine & he suggests for me to do the rebuild. Does anyone know where I can get a master rebuild kit?

[Greasey Harley]

Yeah, that's what I meant, Sm318. Spelling was never my strong suit.

[frankslagoon]

you got it out , might as well pull the shift fork cover and rinse it out with some diesel and take a look at everything. as was mentioned that's a great manual to rebuild. problem is the rebuild kits won't have gears or counter shafts and ya might find those are pitted pretty bad. Muncie 318

[frankslagoon]

you can goggle Muncie 318 rebuild kit and find one for probably 75 bucks but I would see what's up in there first.

[hamjet]

Wow, I didn't realize the SM318 came in our trucks. I thought they were in earlier trucks...

[GreenBay1921]

Here's a peek @ the internals...

[frankslagoon]

Hmmm. maybe it's just the camera, but the countergear looks like it's layen in there crooked is it flopen around like the rear needle bearings are are gone?

[GRX]

The gear teeth look worn but I have run worse. Be sure to clean all that contaminated oil out best you can.

[GreenBay1921]

I drove it a bit before I pull the tranny. It always wanted to grind when shifting to 1st from a higher gear, but other than the noises described above it seemed good. My initial plan was to flush it with diesel, then fill it with fresh oil & see how it went. Do you guys think I should go ahead & do the rebuild?

[frankslagoon]

That tranny made noise goin into 1st. when it was new. they are a non-sycnro 1st gear tranny. But 2nd gear noise could be those countershaft bearings the 319 o/d tranny will act like it's got 1st gear sycnro in over drive but it's the nature of the o/d unit not the gear box.