Trans and motor not listed on spid

[71gmcC15]

My 71 gmc with a 307 and a 4 speed manual is not listed on the spid. Now i know the standerd trans is a 3 speed. With the 4 speed being an option. But the 4 speed looks like it is factory. So is it possible the spid is wrong? I don't think the 307 was a standered option. But I can't see any evadence saying it did not come with one besides the spid.

[Steeveedee]

If it came with a V-8 and there is no option listed, the engine will be a 307. You got me on the 4 speed, though.

[71gmcC15]

Ok that makes sense. Standered v8 307 so not listed. Got it. Now on to the 4 speed

[Coley]

Yep, the 'factory' or stock motor would have been the 307.
The only item that would show up on the SPID would be an optional change to that...either up or down. ie: 292-6 cylinder, or 350 or 400, etc.

As for the 4 speed...well there is a chance that the owner took it back to the dealership after he got it to have it (factory/dealer) upgraded to a 4 speed.
The GM dealership would have easy, quick access to all the correct factory parts so it would naturally and expectedly look and perform as an original.

All good
Coley

[71gmcC15]

Originally Posted by Coley

As for the 4 speed...well there is a chance that the owner took it back to the dealership after he got it to have it (factory/dealer) upgraded to a 4 speed.
The GM dealership would have easy, quick access to all the correct factory parts so it would naturally and expectedly look and perform as an original.

All good
Coley

Maby the 3 speed died and under warranty they whare going to replace it. But instead he had them put in a 4 speed instead. If that's what happened

[71gmcC15]

Or it was ordered with the 3 speed. But the guy wanted a 4 speed and as part of the deal he made them swap it over.

[57taskforce]

Or somebody got a parts truck along the way and swapped it over in the driveway... hard to tell what has happened in the last 50 years. I agree it does look factory in that it’s got the correct parts column and all. I wonder if the floor has the correct reinforcements where the high hump bolts in?

[randy500]

Very strange, 3 speed would have a low hump floor and yours looks original due to color and bolts. Your column is black which is correct for your interior color which is black.

[71gmcC15]

That's what I thought. If some one did it in the drive way the did a really good job. As for the hump I'll crawl under it tomarrow and see if it is correct. And take some more pictures

[54blackhornet]

A three speed would have column shifter no ?

[jocko]

Originally Posted by 54blackhornet

A three speed would have column shifter no ?

correct - that's what makes this such a mystery.

I'm going to guess someone swapped the trans and, either at the same time or eventually, the column.

[71gmcC15]

Originally Posted by jocko

correct - that's what makes this such a mystery.

I'm going to guess someone swapped the trans and, either at the same time or eventually, the column.

That could be true. Have to see what the bottom of the hump looks like tomarrow. If that checks out then who knows.

[ElKotze]

I don't know much about all the GMC specifics, but it seems like they did their own thing more often than not, so I'm wondering if on GMC's the standard trans was the 4-speed? At least in '71-'72?

[randy500]

Originally Posted by ElKotze

I don't know much about all the GMC specifics, but it seems like they did their own thing more often than not, so I'm wondering if on GMC's the standard trans was the 4-speed? At least in '71-'72?

I think this comment has a lot of merit, GMC I bet is 4spd standard eq. For 72. GMC always has slightly upgraded features that differentiate it from a Chevrolet. Look for the build sheet under the seat or behind it, I have never seen one on the gas tank but have heard people say they can be found there too.

[71gmcC15]

Originally Posted by randy500

I think this comment has a lot of merit, GMC I bet is 4spd standard eq. For 72. GMC always has slightly upgraded features that differentiate it from a Chevrolet. Look for the build sheet under the seat or behind it, I have never seen one on the gas tank but have heard people say they can be found there too.

Maby your right gmc could be different. As for the build sheet it's long gone. The only thing I found when I removed the seat was a no hunting sigh. Unless it's behind the gas tank. Maby a GMC expert could shine a little light on it.

[71gmcC15]

Ok I found two GMCs i don't know the year but they list HD 4 speed close range. Or is that different then the normal 4 speed. Like iv seen on chevys?

[Steeveedee]

"HD Close Ratio" looks more like an M22 in a car, to me. I wonder what the transmissions actually looked like in those trucks.

M38 was a 350 trans, M40 was a 400 trans in cars. Trucks used M49 for either one. Different numbers, so maybe the M28 is truck speak for car type M22. That would be pretty cool to have a rock crusher trans in a truck.

[randy500]

I agree that your ur cab came with a high hump floor, those plates are spot welded to the floor, Very hard to duplicate it and why would you way back then and on such a basic truck?

[71gmcC15]

I could pull a house in 1st. I just skip it and use 2nd as 1st. But think that's how these sm465 where l. If there's even a close ratio then that then you could pull a small moon.

[57taskforce]

Isnt the close ratio the np435?

[71gmcC15]

Maby. I don't realy know. I'm pritty shure mine is a sm465. but I could be wrong

[Mike C]

Yes, the HD close ratio trans is the NP435. That being an optional trans still doesn't answer the original question. Very interesting.

[71gmcC15]

Ok that is ruled out then. Man I would think that some one would know. Thare most be an answer. I'm gusing it could be two things. Ether the spid has a error and don't show it. Or 71 GMCS standered transmission is the 4 speed. Second option is more likely.

[Mike C]

Half ton 307 with standard 4 speed is unlikely as their are LOTS of 71 GMC with unmarked SPID for engine and trans but to our knowledge only 1 (yours!) seems to have a 4 speed.

Very unusual because it looks like a factory high hump floor which would not have been the case with the 3 speed.

[71gmcC15]

So the spid could be wrong.