1987 c10 manual 4 spd.. factory trans?

[NASTY-LSX]

Looking to buy a 87 TBI c10 model truck. I found 1 with a 5.7 and 4 on the floor. Did gm make 4 speed models then. Are they rare to find if so?

[Keith Seymore]

Was it an M20 (with the granny low) or a New Process A833 (with the overdrive)?

Either one was available.

M20s are pretty common; MY6s are kinda rare, especially in 1987.

K

[NASTY-LSX]

Originally Posted by Keith Seymore

Was it an M20 (with the granny low) or a New Process A833 (with the overdrive)?

Either one was available.

M20s are pretty common; MY6s are kinda rare, especially in 1987.

K

Not sure. Im looking to buy a 87 to convert to a stepper and found a nice fleetside with a 4 on the floor. Its just a fully loaded silverado, not sure what kind of 4 speed it is. im tired of my DD 9 MPG K20 4x4 lol

[TwoFiftyShifter]

Originally Posted by Keith Seymore

Was it an M20 (with the granny low) or a New Process A833 (with the overdrive)?

Either one was available.

M20s are pretty common; MY6s are kinda rare, especially in 1987.

K

Keith,

You could order an M20 4speed in a C10??? A close ratio Muncie car 4speed?

Say it isn't so!

[brakenit]

M20 doesn't mean a Muncie M20, it was the RPO code for the Muncie SM465.

[TwoFiftyShifter]

Oh, I see now. He did state granny low.... SM465. I got excited there for a minute!

[Keith Seymore]

Originally Posted by brakenit

M20 doesn't mean a Muncie M20, it was the RPO code for the Muncie SM465.

Correct.

K

[Keith Seymore]

Originally Posted by NASTY-LSX

Not sure. Im looking to buy a 87 to convert to a stepper and found a nice fleetside with a 4 on the floor. Its just a fully loaded silverado, not sure what kind of 4 speed it is. im tired of my DD 9 MPG K20 4x4 lol

Did it have a big long round dump truck looking shifter, or more of a short flat passenger car like shifter?

[NASTY-LSX]

Originally Posted by Keith Seymore

Did it have a big long round dump truck looking shifter, or more of a short flat passenger car like shifter?

this is it

[Keith Seymore]

M20/SM465. Essentially a three speed with an added creeper gear (low is 6.22:1).

Nice looking truck


K

[TwoFiftyShifter]

Isn't it pretty uncommon though to have that creeper box 4spd in a C10? Seems like a C20 or K10/K20 it would be commonplace but C10s were mostly 700R4 right?

[Edahall]

Originally Posted by TwoFiftyShifter

Isn't it pretty uncommon though to have that creeper box 4spd in a C10? Seems like a C20 or K10/K20 it would be commonplace but C10s were mostly 700R4 right?

Yes that's correct. The SM465 is a tough transmission compared to the 700R4. You would be able to add much more power without fear of breaking the transmission.
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[Bigstevex4]

Have the 465 in my 83 c10 long box and my 90 jimmy . Once you get use to it there ok,

[Tom]

Originally Posted by TwoFiftyShifter

Keith,

You could order an M20 4speed in a C10??? A close ratio Muncie car 4speed?

Say it isn't so!

There is no such thing. The M20 is a wide ratio 4 speed. The M21 and M22 were close ratio's. Our trucks came with SM465's, not sure why anyone would quote the order code vs the actual trans model but to each their own. They are nowhere near as strong as people make them out to be btw. I broke the original sm465 in my 78 very quickly with maybe 320hp at the time.

Originally Posted by TwoFiftyShifter

Isn't it pretty uncommon though to have that creeper box 4spd in a C10? Seems like a C20 or K10/K20 it would be commonplace but C10s were mostly 700R4 right?

No, it was the only manual transmission offered for a time. Yes most trucks were automatics but this gen only had the 700r4 for a couple years, the vast majority of auto's were th350's.

[Bigstevex4]

I pulled the one out of my jimmy to rebearing it at 120 k on a rebuild kick every thing looked brand new had one in a 85 ford I ton service truck weighed 20,000 pounds I destroyed rear ends broke axles twice drive shafts over drive units 3 clutches broke rear wheels twice blew Navistar up at 140,000 when they sold it changed trans oil maybe twice that's it. Any body that thinks there not tuff are seriously mistaken!

[Keith Seymore]

Originally Posted by Tom

There is no such thing. The M20 is a wide ratio 4 speed. The M21 and M22 were close ratio's. Our trucks came with SM465's, not sure why anyone would quote the order code vs the actual trans model but to each their own.

M20 was the RPO code for the SM465, in the same way M62/M64 were for the Saginaw 3 speed trans; MY6 was the Mopar New Process A833.

I've been with GM Truck engineering for almost 40 years so I tend to gravitate towards the RPO codes rather than the specific manufacturer. That's how it was referred to in the assembly plant.

As you (probably) know - RPO codes get reused across different model years and product lines, so the participants have to know the context of what is being discussed.

K

[MalibuSSwagon]

When I got my 1986 C10 I also thought it was extremely odd it had the SM465 factory installed, but since then I've seem several others so it seems fairly common, I think the vast majority were custom ordered like mine by guys thinking they were getting the "M20" four speed and were sorely disappointed when it turned out to be a HD truck transmission.

[Tom]

Originally Posted by Keith Seymore

As you (probably) know - RPO codes get reused across different model years and product lines, so the participants have to know the context of what is being discussed.

K

Yes, which is why we normally refer to trans models vs RPO codes. A Muncie M20 is a wide ratio 4 speed regardless of the vehicle its in or the rpo code when ordered, lessening confusion during discussions. My M20 came out of a '64 corvette originally, but I don't quote the corvettes rpo code when talking about it. Your contributions to this board mean you can reference things any way you'd like though

[tucsonjwt]

SM465 is not the best transmission for fuel economy. The first gear is never used, so you really only have 3 forward gears. A lot will depend on the rear axle ratio you have. The heavy duty SM465 often had a "low" rear axle ratio, like 4:10, which will result in poor fuel economy.

[Keith Seymore]

Originally Posted by Tom

Your contributions to this board mean you can reference things any way you'd like though

I appreciate that. I'm afraid I can't change at this point.

K

[Bigstevex4]

Originally Posted by tucsonjwt

SM465 is not the best transmission for fuel economy. The first gear is never used, so you really only have 3 forward gears. A lot will depend on the rear axle ratio you have. The heavy duty SM465 often had a "low" rear axle ratio, like 4:10, which will result in poor fuel economy.

My c10 came with 273s it had a 6 in it you need along flat run to be in 4th put in a slightly hoped up 350 its a great combo start second shift at 30 mph you can run 3rd past 85 at 75 your doing 2300rpm in 4th

[tucsonjwt]

My 83 454 C20 SM465 with 4:10 does not like to go past 30 mph in 3rd gear. The gear vendor I have only works at about 30 mph or higher, so it only gets used in 4th gear. You can see the radical difference in having an "open" or "highway" rear axle ratio in the 2.xxs compared to the "towing/hauling" rear axle ratios of 4:10 or 4:56.

[1976gmc20]

I had a 1980 K10 with 350/465. I dunno what the axle ratios were but I suspect two point something because you had to be 30++ mph to hit 4th. You could run up to about 60 very comfortably (I don't like to over-rev engines) in 3rd, and likewise about 35 in 2nd. 1st of course was just for crawling or starting on a steep hill. Surprisingly, it towed heavy loads quite well because on hills you could downshift and still pretty much keep up with traffic.

It also got about 18 mpg

[TwoFiftyShifter]

Originally Posted by tucsonjwt

SM465 is not the best transmission for fuel economy. The first gear is never used, so you really only have 3 forward gears. A lot will depend on the rear axle ratio you have. The heavy duty SM465 often had a "low" rear axle ratio, like 4:10, which will result in poor fuel economy.

I've owned 3 SM465 equipped trucks. An 80 K10 with 2.73s, and 87 V20 with 3.42s and my current 84 K10 with 3.08s. The fuel economy seems to be just fine, maybe better than a TH350 even. The gears are gapped pretty fierce, though.

[tucsonjwt]

I would add that a 3/4 ton pickup will never get the fuel economy of a 1/2 ton pickup, all other things being equal.