What tranny do I have?

[shifty]

My speedometer doesn't work. I think it's the gear inside the tranny that's not working.

I took the cable off at the tranny, clamped a drill onto it and slowly spun it - the needle jumped, so ... I know the cable and gauge seem to be fine. I'm pretty sure the cable is long enough, it sticks out enough that it looks like the gear in the tranny should have enough to grab onto.

I need to tell the guys at the parts store what tranny I've got (it's attached to an L6 250).

Or does it even matter? Would the gear be the exact same for snchryonized and unsynchronized trannys?

What size or model is my tranny?

[CHEVY & GMC FOREVER]

[toms68cst]

I'm having the same problem. There's a short pin between the transmission and the external speedo gear that tends to shear. I guess it's from sitting alot with crusty grease in the grears. Mine's sheared before and now it's broken again. The last time it happened I bought one from the Chevy dealer but I checked again and they didn't have one. Someone else suggested a transmission shop. I'm sure you could find one at a junkyard if you looked around enough.

[shifty]

Okay, I can't really easily take pics. When I bought a newly rebuilt and customized L6 250 for it today ($300! Score!) I was talking to the guy and he said I had the "larger saginaw synchronized trany" in it.

The only other info I could give is this:

On the metal badge attached to it (near to where the speedo cable reaches the gear on the tranny) This number is punched into the badge: 3968010 Y

There is a GM part number stamped into the tranny, but I can't tell for sure if it was correct - low light outside and lots of paint and gunk. It looked like: GM 3952648

Thanks for any info anyone can provide.

Yanking out the old engine (wee, starting to yank it out) today was a blast! Glad my friend has a cherry picker. Need to go buy a stand so I can rebuild it.

Scary enough, I noticed I had a leak somewhere around the tranny. Looks like oil...guessing this tranny doesn't use normal fluid.

[Longhorn Man]

We are asuming it is a 4 speed....
does it have a real low granny first gear?

[CE20934]

He has the three speed, not the four.

Gimme a minute & I'll look it up.

[CE20934]

Originally Posted by shifty

Okay, I can't really easily take pics. When I bought a newly rebuilt and customized L6 250 for it today ($300! Score!) I was talking to the guy and he said I had the "larger saginaw synchronized trany" in it.

Sounds like an SM326 to me. How many bolts hold the side cover on? Is it synchronized in all gears?

On the metal badge attached to it (near to where the speedo cable reaches the gear on the tranny) This number is punched into the badge: 3968010 Y

I have a listing for a 3968008 (3spd Saginaw used in the vans), but not a 3968010. My list is by no means complete though.

There is a GM part number stamped into the tranny, but I can't tell for sure if it was correct - low light outside and lots of paint and gunk. It looked like: GM 3952648

I have a listing for a 3925647 (Saginaw SM326 case). Again, my list is by no means complete.

Scary enough, I noticed I had a leak somewhere around the tranny. Looks like oil...guessing this tranny doesn't use normal fluid.

I'd consider 80W-90 "normal fluid".

Hope this helps.

[Josh]

Originally Posted by shifty

Okay, I can't really easily take pics. When I bought a newly rebuilt and customized L6 250 for it today ($300! Score!) I was talking to the guy and he said I had the "larger saginaw synchronized trany" in it.

The only other info I could give is this:

On the metal badge attached to it (near to where the speedo cable reaches the gear on the tranny) This number is punched into the badge: 3968010 Y

There is a GM part number stamped into the tranny, but I can't tell for sure if it was correct - low light outside and lots of paint and gunk. It looked like: GM 3952648

Thanks for any info anyone can provide.

Yanking out the old engine (wee, starting to yank it out) today was a blast! Glad my friend has a cherry picker. Need to go buy a stand so I can rebuild it.

Scary enough, I noticed I had a leak somewhere around the tranny. Looks like oil...guessing this tranny doesn't use normal fluid.

Is this a 4 spd or a 3spd? The only reference to 3952648 I have is the side cover for a muncie 4spd.....

Josh

[CE20934]

Assuming this is the truck & the picture is current, he has a 3spd.

[shifty]

Thanks, guys. I do have a 3spd on the column. It has a granny gear or "Metro Detroit traffic gear" (1st gear ), then 2nd and 3rd. It's possible to start in second without tearing up the clutch, but it gets much easier to do so after the engine is warmed up.

We ripped out the original engine to replace it with another rebuilt 250 L6 this weekend. The new engine is in, but not finished hooking up the 3or 4 wires and one vacuum hose yet Gotta set the the timing and re-run the gas line too. Replaced the clutch while I was in there too. This gave a good chance to look at things.

There are six bolts to hold the bell housing to the block, two longer bolts and four shorter bolts. The bell housing was easy to remove, but I forget how many bolts held it in. There was a lot of grease inside it from the bearing and fork tossing grease all over. There was a piece of flashing that was held in by two bolts and the three bolts from the starter.

At the back-center of the bell housing, there is a disk-shaped part of the tranny with four bolts. On the passenger side of the tranny there is something that looks like a sensor with a male spade-type of tab (looks almost like the temp sensor on my engine, the one on the head, manifold-side) - this transmission sensor is closest to one of the large rods/tubes that comes down from the column. I would swear this was some shift indicator or temp sensor, but that's not an option in my truck (this isn't the only thing I've found in my truck that isn't hooked up - there are several other things like power steering brackets, several vacuum hoses coming out of the cab, etc.) The sensor is not hooked up.

The ratio gear that the speedometer hooks into is on the driver's side of the tranny.

I don't have any other information, but if you can think to ask anything, I'll be happy to answer.

Two people thus far have said it's a saginaw syncrho'd tranny - one here and the guy I bought my rebuilt engine from. I'm not sure what it is.

Josh - I found the same code you did on Google. Don't know what to think of it though. My truck can definitly only shift into (3) gears. It looks like it's possible to setup a floor shifter for the tranny, but ... I dunno. I wish it was a four-on-the-floor

[CPNE]

Seven bolts on shift fork cover=saginaw. Does it look like this? If so, it's not the original tranny that would have been in a 68. It's the 69-up syncro'd sagniaw version.

[shifty]

I think I took a picture of the bell housing.

WAIT! I have more information:

The Haynes manual for my truck said my tranny would have a little clip on the back of the fork to release it, but it sure as hell didn't have it there. The fork looked really damned new. We have to complely remove the bell housing from the tranny to get the fork off the bearing so it could be replaced.

I only bothered because the clutch was slightly worn, although all of the other parts were in good repair. If nothing else, I have a spare 10" clutch, its bearing and all of the other parts laying around .

I will try to take pictures tonight. I have some from the front when the engine was out, but ... As always, thanks for the tips.

[shifty]

Oh - and when you say "shift fork", what do you mean? When I was talking about forks in my last post, I was talking about the clutch fork. Guess they're two diff't things?

[CPNE]

Originally Posted by shifty

Oh - and when you say "shift fork", what do you mean? When I was talking about forks in my last post, I was talking about the clutch fork. Guess they're two diff't things?

Shift forks are what your shift rods from the column attach too. They are inside the transmission and move the gears. The cover is on the driver side of the tranny. If this cover (over the shift forks) is removed you have access to the guts of the tranny. 7 bolts here=saginaw.

This has nothing to do with bell housing or clutch fork.

[shifty]

Ok, will check it out. I'll just take pictures of the whole damned thing tonight, including the new engine and everything. It still has the original rusty ass manifold on it, but the "new" one had a crack in it, so I used the old one.

Will post pictures. Would be grateful to have your input once they're up.

Ttt

[CE20934]

Originally Posted by shifty

On the passenger side of the tranny there is something that looks like a sensor with a male spade-type of tab (looks almost like the temp sensor on my engine, the one on the head, manifold-side) - this transmission sensor is closest to one of the large rods/tubes that comes down from the column. I would swear this was some shift indicator or temp sensor, but that's not an option in my truck (this isn't the only thing I've found in my truck that isn't hooked up - there are several other things like power steering brackets, several vacuum hoses coming out of the cab, etc.) The sensor is not hooked up.

That's the switch for your backup lights.

[farside847]

Originally Posted by CE20934

That's the switch for your backup lights.

I thought that was on the column...

[shifty]

Okay, maybe this will settle my question. I'm really sorry for taking so long to post pics, guys. I will post the three best pictures and link some more up at the bottom. The pics might take a sec to load.

Bell housing, clutch fork, etc:


Driver side rear-to-front shot of tranny:


Passenger side rear-to-front shot of tranny:


Side plate of tranny - this is where the number above is pulled from that Josh ID'd(note the metal badge, I posted number previously also, it ends in a "Y"):


Here are a couple more pictures that turned out crappy, but you can make out 6 bolts...I think there's a 7th on the front, but I couldn't see it from the angle I was at ---- and the camera ran out of damned batteries before I could finish!!!!!

http://www.shifty.org/pics/68chevy/e...swap%20021.jpg
http://www.shifty.org/pics/68chevy/e...swap%20022.jpg

[shifty]

Oh - and I dunno if you guys like looking at pictures a much, but here are some pics of before and after the swap - it's 80% done. Took about 10 hours of solid work to get this far. Ran into a lot of obstacles along the way wiht parts not fitting. The only thing that isn't good at this point is the harmonic balancer - The one on the new engine doesn't match up with the old engine or the alternator.

Anyways..
http://shifty.org/pics/68chevy/eng_swap/

Ignore my friend John, he's the nut that's trying to hump the new motor

[CE20934]

Originally Posted by farside847

I thought that was on the column...

Well, the way he described it, it sounded like that switch to me.

I know the automatics had it up in the column, but I'm not too sure the three-on-the-trees did.

[CPNE]

Thats the 69-up syncro'd saginaw and that switch is for the TCS emmissions found on 71-up as the backup switch for the 3 speed is on the column.

[shifty]

Sweet! Any cool stuff you can tell me about this tranny? Like....

Does this tranny normally require a tall hump to fit?

Is it possible to use a floor shifter with it?

What should I search for in Google to learn more about this thing (e.g. is there a part number or casting number I should look for)?

should I take it to a shop if I want to rebuild it, or is it something I can do safely with a guide?