sm465 just a little too short

[Rustywer]

Hello, just purchased a 77 C30 with a 350 and the saginaw 3 speed with the granny. So I figured out it's a ch465 and I need something a little taller, but need to tow trailers for work. I would like to know if a sm465 rpo mm7 replacement will require a different drive shaft? The clutch splines should match and the replacement should be a relatively easy bolt up to the bell housing. Other concerns would be the cross member and rear trans mount.

The truck is a stock 77 C30 Standard Cab short wheel base.

Any help would be appreciated. My last chevy was a 69 C10 my 6 year old daughter named Tinkerbell, my 7 Year old Grand Daughter named this one Charlie Brown.

Rusty

 

[DoubleDingo]

It appears the CH465 is the SM465...http://www.novak-adapt.com/knowledge/sm465.htm

 

[Rustywer]

I understand that they are the same, but my concerns are with the spline count on the input and output shafts. I have heard that there are three different splines used. The MM7 I believe was used in the P series units. I'm looking to forego the granny gear and gain the .73 fourth gear. That should make it a little better on the highway and drop the rpms to a reasonable level at 65 to 75 mph. Is anyone familiar with this swap?

 

[DoubleDingo]

Out of curiosity, I did a google search this morning for a mm7 transmission, and this was the second down on the list...http://www.gmsquarebody.com/forum/showthread.php?t=3422

 

[Rustywer]

I see the spline pictured is a 10 spline. That would mean that it is a 4WD Trans. I believe the 35 and 10 splines were 4WD and the 32 was the 4X2. Im really looking for something thats plug and play. I know, nothing is that easy. Someone has had to have run through this before. My 77 is about 8 mpg with 1 tow of 23 miles on the last tank. So who out there in squarebody land has run through this before?

 

[bucket]

The overdrive trans is not a direct bolt-in, and it's the input that is 10 spline, like the input on the other truck transmissions. The 4x4 unit has a 32 spline output with a flange to bolt to the t-case, the 2wd unit has a slip yoke style output shaft that I believe is also 32 spline (if not, it's 27 spline).

The SM465 came with a few different output shafts. 10 spline and 32 spline outputs were used in 4x4 apps and 2wd was usually a fixed yoke style output that used a goofy spline count, 31 I think.

 

[HotRodPC]

Wow, Whoa Nelly. Hold the phone. Got my head spinning with all these wrong model #'s and names of each and such. You have a Muncie SM465 Now, not a Saginaw and not a CH465. the MM7 is for a 4wd and is not a Muncie. It's a New Process, and you're looking for RPO code MY6 for the 2wd NP as in New Process A883 transmission that is a 4 speed having an OD. So now, where were we???

Ohh you're wanting to swap out the Muncie SM465 with the Granny Low 4 speed, for a New Process A883 4 speed with OD. And yes, the 2wd version of this transmission I'm pretty sure is a 27 spline bucket. The 4wd is not, it is 32 spline. And most likely will bolt into his bell housing as most of the 2wd models used the Chevy bell pattern. The aluminum ones did anyway. Use the same clutch too. Then all he has to deal with is the shifter and driveshaft length which will be the same length as the Th350 passenger car 6in output shaft. So it'll need to be 3 inches longer than a squarebody driveshaft. Being a 1 ton, I'd stick with a 2pc driveshaft and your modified to fit the trans if you did this route. To be honest, for a 1 ton, I'd go with an NV4500 New Venture 5 speed with Granny Low and Overdrive. Very strong unit, going to much easier to find than the MY6 New Process A883 trans, not to mention stronger.

 

[HotRodPC]

The overdrive trans is not a direct bolt-in, and it's the input that is 10 spline, like the input on the other truck transmissions. The 4x4 unit has a 32 spline output with a flange to bolt to the t-case, the 2wd unit has a slip yoke style output shaft that I believe is also 32 spline (if not, it's 27 spline).

The SM465 came with a few different output shafts. 10 spline and 32 spline outputs were used in 4x4 apps and 2wd was usually a fixed yoke style output that used a goofy spline count, 31 I think.

BTW, the SM (SynchroMesh) 465 2wd spline output is wierd as you said. It's fine spline 35. Very strange but that's what it is for all year models that I'm aware of. And 99% positive 2wd A883's are 27 spline and the same length as Muncie M20, M21 and M22 along with Saggy 3 and 4 speed side loaders. This makes them the same length with bellhousing as the Th350 6in output shaft. Many don't know, you can swap 27 spline Muncies and Saginaws right into where Th350 w/ 6in output shafts go and no need to mod the driveshaft or change yokes.