Is there a difference between the sm465 and the ch465?

[72timemachine]

I've done some research, however there seems to be little to no difference from what people in some of the forums are saying about the difference in these two transmissions.

The one I have came out of a 1969 c60 dump truck, I believe it was a 2 1/2 ton. It looked like it had a 2 speed rear end, just massive. The engine was a 366 ci mated to the ch465.

Now I am no way an expert on this but is this a 4 speed manual transmission? I believe it has the 13" clutch, very odd looking too. The stick shift lever is straight up and down, no curves in it at all. Shift nob was missing. It has a pto with a small drive shaft attached to work the dump bed hydraulics. It also has the emergency brake drum attached to the tail shaft. I swear this thing weighs almost as much as a small block Chevy engine. It took 3 guys to pick it up and throw it in my truck, I feel I may have been the only one lifting though.

There has to be some difference, otherwise, why would GM bother. Does "ch" designate GMC or something, whereas "sm" designates Chevrolet?

Thanks for any help.

[HO455]

Does this the transmission in the link match your transmission? I know the SM420 was used in trucks a large as 2 1/2 tons but I don't believe the 465's were. Not to say you didn't find one installed, but it may not have been factory (and I was wrong earlier today so I could be wrong about this too). Send the folks at Novac an email if you need more information. They have been good to me with parts and info on SM420's over the years

http://www.novak-adapt.com/knowledge...s/manual/sm465

['68OrangeSunshine]

Originally Posted by 72timemachine

I've done some research, however there seems to be little to no difference from what people in some of the forums are saying about the difference in these two transmissions.

The one I have came out of a 1969 c60 dump truck, I believe it was a 2 1/2 ton. It looked like it had a 2 speed rear end, just massive. The engine was a 366 ci mated to the ch465.

Now I am no way an expert on this but is this a 4 speed manual transmission? I believe it has the 13" clutch, very odd looking too. The stick shift lever is straight up and down, no curves in it at all. Shift nob was missing. It has a pto with a small drive shaft attached to work the dump bed hydraulics. It also has the emergency brake drum attached to the tail shaft. I swear this thing weighs almost as much as a small block Chevy engine. It took 3 guys to pick it up and throw it in my truck, I feel I may have been the only one lifting though.

There has to be some difference, otherwise, why would GM bother. Does "ch" designate GMC or something, whereas "sm" designates Chevrolet?

Thanks for any help.

Just in marketing jargon. The ''CH'' was for Chevrolet. SM was for Synchro-Mesh. [Not Saginaw-Muncie, as the former transmission plant was in Michigan, and the latter in Indiana.] SM 420s and 465s were Muncies.

I think the marketeers didn't want to confuse the 'nice people' with messy mechanical details like synchronizing gears -- since they probably didn't understand it much themselves. Just sell it as a genuine CHevrolet tranny.

Tailshaft parking brakes were on some SM420s but not [if I'm assuming correctly] on the SM465s. The 420 was physically shorter, and had lower ratios on the lower gears, than the 465. MY 1968 was the first year for 465s on production light trucks. For heavier trucks, some 4x4s, and Canadian production, they used up the remaining 420s in their logistics line, ending in 1969.
I could be wrong -- without seeing the tranny in question. I don't see why GM would not use the SM465 on later big trucks. It was certainly built to handle just about anything.

[geezer#99]

Maybe it’s a new process or Clark 5 speed.
A pic of the tranny will clear that up.

[72timemachine]

Thank you for all of your input. I will try to get some part numbers off the transmission and a photo. Novak is a great resource and I have been to the website many times, thanks for the info on that as well.

I do feel the transmission was original to the truck but again, a vehicle this old could have had anything changed throughout it's lifespan. I found a tag on the transmission after I brought it home from the boneyard and called the repair shop who attached it there. The guy told me that he rebuilt it 25 years ago. Before I killed myself getting it out with no tranny jack, just 2 ratchet straps, I took the top cover off and all the gears still looked perfect, although the clutch was smoked. I was not prepared to take out such a beast that day but did not want the crusher to get it so I dove in.

['68OrangeSunshine]

The ''tell'' is the Reverse position. Towards the driver, it's a 420. Away from the driver, it's a 465.

[72timemachine]

I finally got a chance to get some numbers but I need to attach a url to the photo to post it on here, not sure how to do that just yet but if any of you can tell me what the production date is, that would be great. I cannot seem to find anything online about decoding it. Here is how it appears on the passenger side of the case.


D254
GM
6273212

Thank you.

[Seanext]

I picked up a 292 mounted to 465 out of a 68 Chevy big dump truck. Not sure if it was a C50 or C60. I am rebuilding both for a 4X4 project. It has the brake mounted on the back of the tranny like yours. As I am using it in a 4X4 I had to change the top shaft. I have rebuilt several of the 465 but this one was a little different. When I cleaned it up on the out side it had HD stamped on the outside and on the bottom counter shaft the first gear has a metal piece almost like a seal pressed on the back of the gear. On the shaft there was a spacer with rubber tabs that aligned with the piece on the back of the forward most gear. It looks like it was made as some kind of cushion to maybe help from grinding gears. Never seen this before and can't find anything in any of my books. I am not sure if this was only for big trucks or it has anything to do with the painted HD stamp on the side.

[STPETEBLUE]

This article may help:
http://www.novak-adapt.com/knowledge...s/manual/sm465