Does anyone know if a PTO for a SM-420 will bolt onto a crash box transmission and function like it's supposed to? The doodlebug tractor I've got on the drawing board is going to run a Mercruiser 4 cylinder engine, a turbo 350 main transmission, and a crash box as a second trans. I'd hate to waste a good 420 on an application that will never get up enough speed to need a synchronized gearbox, and I've got a few of the old crash boxes stockpiled, and PTO-equipped 420's. I'm planning to fabricate a PTO drive for 3 point hitch implements such as a garden tiller and possibly a small bush hog. A power steering pump mounted to the engine will supply hydraulic pressure for a home-brewed 3 point hitch. If the PTO mounting is different, I'll be in the market for one that fits the old crash box. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jerry, I'd be more concerned about the gear pattern matching up between the 420 PTO and the older crash box tranny. I'm not familiar with them but older trannies often had straight cut gears rather than helical cut ones. The bolt pattern on PTOs has been pretty standardized for years.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
All the PTO drives on the cluster gears I've seen had straight cut gears. Trying to mesh a set of helical gears to engage a PTO would be difficult, if it could be done at all. That's one reason a transmission is noisy when the PTO is engaged. On the big rigs I've worked on, sometimes there's an adapter with an idler gear between the main box opening and the PTO, especially on one that can turn both directions to run a winch, etc. Jerry
Edit: I just found a crash box PTO on Ebay from a 1937 4 speed. It looks somewhat different that tne one for a 420, so I bought it. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
My ‘54.1 has that idler gear, works great, never could see how PTO would work ‘til I saw idler on EBay, never found any info indicating it’s existence.
Ed
Last edited by EdPruss; 09/04/20223:26 AM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Hotrod, I will gladly trade you a pto for a crash box for a sm420 pto. We need to meet up someday for the lathe head. I am headed to Atlanta next month but that may not help you much. I can leave it at my son in law --lathe head and pto - for whenever you may get there. You could leave the sm420 pto.
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Thanks for the offer. I found a single direction unit on Ebay and bought it. I'll be running a PTO shaft on a doodlebug tractor I'm building, so there won't be a need to run in both directions. I've got a big 3-point garden tiller that will be the main implement driven from the shaft, and maybe a small bush hog. One of the main duties for the tiller will be preparing feed plots for deer and turkey along the edges of the woods near some permanent deer stands and blinds we've hunted from for 30-something years. I'll be running a home-brewed 3 point lift powered by a power steering pump and operated by a small hydraulic cylinder. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
