1969 Saginaw 3-speed, no drain plug?
 

Hi guys, headed into the garage this afternoon to change the transmission oil (1969 c10, 3OTT transmission) - 80w-90 gear oil

I get under the car and to my surprise, I don’t see a drain plug? There is a fill plug. I guess the early Saginaw 3sp transmission may not have had a drain plug?

What then is the recommended method to change the oil?

Also, I notice that one of bolts (transmission to bellhousing) has a snapped off head. The fun things you discover when you buy a 56yr old vehicle.

Thank you

Re: 1969 Saginaw 3-speed, no drain plug?
 

Are you sure the "snapped off bolt" isn't just coming from the other direction? Not sure about your drain plug issue.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Mine had a drain plug in about the location of the. The two bolt looking ones close together, the upper was my drain plug. I wonder is someone put another type of bolt instead of the pipe plug in there.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Interesting, I’m not aware that there is a bolt that’s accessed from the inside of the bellhousing? I guess if the head snapped, it probably would have done so flush (here a short length is protruding)

Can anyone confirm what this is in the picture?

Re: 1969 Saginaw 3-speed, no drain plug?
 

Grok says the following

Re: 1969 Saginaw 3-speed, no drain plug?
 

The bottom bolt that connects the tail shaft to the main housing can be used as a drain plug.

Re: 1969 Saginaw 3-speed, no drain plug?
 

I remember putting clutches in pigs like this with the bolts threaded into the trans. It's a real time-eater when you're working against the clock.

Re: 1969 Saginaw 3-speed, no drain plug?
 

I just got under the truck again.

Confirmed that the two lower transmission bolts are coming from the inside (can’t see the bolt heads). The two upper bolts are coming from the outside (can see the bolt heads).

Seems to match what Grok is saying.

Why did GM do this? I’ve never seen this before in any car I’ve ever worked on before this one. Really threw me for a loop when I first saw the end of the bolt staring at me in the face lol

Re: 1969 Saginaw 3-speed, no drain plug?
 

When I still had the 3 speed, in my '70, I drilled and tapped that blank boss for a '98 GM style magnetic tip O-ring equipped oil drain plug.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Every manual transmission bell housing bolt this way, all my 4 spds and three on the column trucks, I'm sure the General had some reason for this bolt pattern

Re: 1969 Saginaw 3-speed, no drain plug?
 

^ On most trucks? I've seen them both ways, and every standard trans I had in a car, the bolt heads were outside the bell housing.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Both my 70 step side, 6 cylinder truck, and my 64 C10 had the bolt heads on the outside. The 70 V8 I have now had the bolts backwards (to me anyways) with heads inside the bell housing, rear engine mount thing. Maybe twhether it was originally a V8 versus 6 banger was a difference. NOt sure, just know that the 69 3 speed I put in my 64 (which had a V8 by the time it got to me) was with heads out. AS mentioned, all cars I have had had them outward.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Interesting…

It makes me wonder what is the sequence to removing the trans when two of these bolts are coming in from the inside.

Say I’m doing a clutch job… I’m sure it’ll all make sense once I finally get in there one day.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Yes, correct. I just looked at my sm318 overdrive transmission from a tri five Chevy car and all mounting ears are threaded

Re: 1969 Saginaw 3-speed, no drain plug?
 

All four heads are inside the bell housing? Oh, what joy.

Re: 1969 Saginaw 3-speed, no drain plug?
 

Yeah, I imagine a PITA. I acquired this transmission a little over a year ago, without bell housing, who knows what has been done to it in the past 70 years. Still figuring things out Plan on installing in my 67 with 3ott, bottom picture