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

[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]

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!

[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.

[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

[brakenit]

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

[Keith Seymore]

Originally Posted by brakenit

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

Correct.

K

[TwoFiftyShifter]

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

[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,

[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!

[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

[Bigstevex4]

My jimmy with throttle body 5.7 465 has 410s but it has 36 inch tires gets around 10mpg but its 8 feet high,

[1976gmc20]

Originally Posted by Bigstevex4

My jimmy with throttle body 5.7 465 has 410s but it has 36 inch tires gets around 10mpg but its 8 feet high,

It's pretty hard to get really good mileage from a Squarebody at interstate highway speeds

My aforementioned 1980 K10 (350/465) with the tall gearing got a solid 15mpg at 80mph, but around 18mpg at the then legal 55. That's with a carb

The TH350 automatic K20 and K10 were lucky to get 10mpg under any conditions, and would downshift on moderate Colorado hills. They were really good at converting gasoline into noise.

[Tom]

You guys worry about mileage too much. My 78 was originally a 385 with the sm465 and 3.73's. I got 10mpg everywhere I went. Then I bought a 79, put a vortec 350 converted to carb in with stock 3.07 rear gears and th350. It also got 10mpg in town. Then I put a built 200-4R in, and it still got 10mpg in town.

[1976gmc20]

Originally Posted by Tom

You guys worry about mileage too much. My 78 was originally a 385 with the sm465 and 3.73's. I got 10mpg everywhere I went. Then I bought a 79, put a vortec 350 converted to carb in with stock 3.07 rear gears and th350. It also got 10mpg in town. Then I put a built 200-4R in, and it still got 10mpg in town.

Worry ???

I get roughly half again the mileage out of a four speed manual versus the three speed automatic. Maybe only a margin of 5mpg but it's a lot of difference percentage wise (300 miles vs 200 miles for a tank).

The four speed automatic is a lot better on gas mileage than the old TH350.

Something's wrong if you're only getting 10mpg in a pickup with a manual. Maybe you're running it up too high before shifting...? I can shift my C-20 out of 2nd (don't normally use 1st) at around 8mph, and get into 3rd by 20.

[68post]

Originally Posted by 1976gmc20

Worry ???

I get roughly half again the mileage out of a four speed manual versus the three speed automatic. Maybe only a margin of 5mpg but it's a lot of difference percentage wise (300 miles vs 200 miles for a tank).

The four speed automatic is a lot better on gas mileage than the old TH350.

Something's wrong if you're only getting 10mpg in a pickup with a manual. Maybe you're running it up too high before shifting...? I can shift my C-20 out of 2nd (don't normally use 1st) at around 8mph, and get into 3rd by 20.

I think you're on to something, my 2000 3500HD diesel flatbed, (with an NV4500 trans,4.63 gears,19.5 rim/tall tires), was @10,200 lb with an empty bed center and got 10 mpg. Until I noticed an auto diesel one ton hit 4th gear at about thirty mph. I started short-shifting it and got 15 mpg twice in combined city 'n hiway (set cruise @ 55 or 60 only ,on a 50 mile hiway cruise home).

My last 4wd was a '83 5/4 K30 with 4.56 gears/SM465 and 33" tires and I could sneak a hair over 12 mpg out of it's hi-perf 350 on a hiway trip - with a load.
Everyone else that drove it on the interstate would push the clutch in and start to search for 5th gear - but I'd stop them asap !

There will be an '87 V1500/4.3/A833 for sale soon from my late friends estate , (more rusty than cherry). Those two 4wd's looked very similar - but couldn't have been more different !!

[1976gmc20]

Originally Posted by 68post

I think you're on to something, my 2000 3500HD diesel flatbed, (with an NV4500 trans,4.63 gears,19.5 rim/tall tires), was @10,200 lb with an empty bed center and got 10 mpg. Until I noticed an auto diesel one ton hit 4th gear at about thirty mph. I started short-shifting it and got 15 mpg twice in combined city 'n hiway (set cruise @ 55 or 60 only ,on a 50 mile hiway cruise home).

Yeah, these big tough American engines don't need a lot of RPM for normal driving.

I've had to yell at a few people that I let drive one of my trucks for revving them up like some sports car