Quote:
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.
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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.