The Stovebolt Site Forums The Parking Lot Big Bolts 261 & 5 Speed from a 1961 C60

I've got the chance to get a 261 and the 5 speed that came with it out of an old C60. I hope to be by there next week and confirm that it is a 261 and find out what model 5 speed it is. I know a bit about the 261 already, and that's why I want it. But I don't know about the tranny at all.

Was this a standard / optional transmission to couple to the 261 in a 1961 C60? or has it been "upgraded" at some point in time? Is it any good / better /worse than the SM 420? Any idea on what the low and high gear is (i.e. 7.41:1 low and 1:1 high)?

If it all works out, I plan to put this into my 1958 1 ton. I upgraded my differential to a 4.10 gear (original was 5.13) and want some more torque than the stock 235 has. I hope to get this from the 261 and maybe the 5 speed. Anybody ever put the 5 speed in a 1 ton?

Thanks all!

Hy jhaa_lives, the five speed may have been standard or an option or an "upgrade", if it is an overdrive in fifth type that would be a definite advantage. You will probably have to shorten your driveshaft to install it, the low gear will probably be as low as the 420, hope that helps

Hey jhaa_lives this should give you all the info you need I think it covers every trans GMC and Chevy used from 60 to 66.

http://www.6066gmcguy.org/SM420.htm

HevyHauler has the link for you, check out trannys with the O as in overdrive. Good chance it will be a Clark 5-speed. If it is a 264VO, 280VO etc...on the ID plate, grab it.

The best you can do is a .80 overdrive in fifth, but should bolt up to the 235/261 bellhousing with no mods.

I am going to look at a '59 dump with 261/5-speed also. Hope to find the big "O" as well. Good Luck!

So this may come as a shock to every one, but I'm actually looking for the New Process 540 GL that has the 7.44 first. I have 19.5 rims (33") and a 4.10 diffy. I figure 2500 is not too bad to run the engine at and that'll get me 60 mph. What I want is to make sure I've got that stump pulling torque in 1'st gear. However, if it turns out to be an overdrive, then I can always put my 5.13 gear back in.

I've seen the 6066 gmc guy site many times. An excellent resource. The fact that he is going to put a NP 5 speed in a 3/4 ton is encouragement that I can do it as well on my truck. I figured drive shaft work would be needed.

Now I gotta figure a way to go get it!

Finally got around to looking at this truck last weekend, as I was driving through. I'm glad I didn't make a special trip.

The "original engine" turned out to be a 250 (not even a 292). The front motor mounts were welded to the base of the block.

The "5 speed" turned out to be a SM 420. Well heck, I guess reverse is a speed!

It was an IRWIPI, sunk in the soil with rims rotting away, back end loaded full of junk, and various bits and pieces removed over time.

That is too bad hope the guy just didn't know what he had and made a bad guess. Hate to think he was trying to pull a fast one.