Thinking about PTOs


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Posted by D. Sherman [24.32.202.83] on Tuesday, January 19, 2010 at 15:17:26 :

I took the PTO off my beater M37 to turn the innards around so the output shaft will come out the front instead of the rear. It looks like somebody had already turned it around because they cut the shift lever bracket off of the closed bearing retainer cap. I will have to make a new bracket and weld it on, but other than that it looks to be easy to turn the innards around and use it.

I've been comparing it to my M43, though, and there are several differences. The M43 has the correct LU4 winch, though as we know, ambulances didn't come with winches and the army green paint on the winch doesn't have any blue under it, whereas the bottom layer of paint on the ambulance is air force blue. So, they put an M37 winch on the M43. It looks good and every thing appears to be done right. My M37 has an MU2 winch cobbled onto a home-made bumper with a complicated drive setup involving much torching and welding. I'm trying to simplify the clever but non-working contraption and just make it an ordinary winch.

The PTO on the M37 (with the MU2) is attached to the tranny with studs and nuts that can only be turned a little at a time with an open-end wrench and most of the nuts only come off after pulling the PTO back away from the tranny. There is zero clearance for getting the PTO off past the studs and the frame rail. It took a lot of jockying it around and wiggling to find the one position where it would barely scrape its way out. It was very tempting to take a torch to the frame, but I know that would be A Very Bad Thing. The M43's PTO, by comparison, is a similar mechanism, but there's lots more clearance around the mounting flange, and it's held on with ordinary bolts, which means no studs to get in the way and no interference with the frame. All in all, it's much better setup.

Is the M37 stud-mounted PTO the sort that's normally used on a civilian PW? Is there more frame-to-tranny clearance on the civilian truck, or do they just mount the PTO before putting the powerplant in the truck?

I'm going through the PTO and overhauling it as long as I have it apart, but I was shocked to see that the roller bearings on the input gear shaft are $34 apiece! They've got some rough spots and that gear is constantly engaged and turning, so it seems like they should probably be replaced, but I don't know that it's worth putting that much money into this thing, especially when the tranny itself is probably just as bad. This is the tranny that locked up due to water freezing in the bottom of it last winter, and it has a crack from the drain hole to the passenger side PTO opening. I put clean oil in it last year, but when I drained it this time, the oil looked like mud already. I'm not sure where all the water is getting in. The cowl vent leaks like they all do, but it doesn't drip directly onto the shift tower. I'm thinking I should just seal up the cowl vent with RTV. I never use it, and the RTV probably won't stick very well and would be easy to pull out of I ever decided I needed a vent.

Lastly, what do you think of just welding up the crack while I have the tranny drained? I would use that low-end MIG wire-feed welder. I know the best way to fix it would be to take it off, strip the whole housing, heat it gently, and braze it, but I'm thinking that maybe since the crack ends at two natural openings, the heat of welding won't cause the crack to propagate past the drain hole or the PTO hole, and the wire-feed seems to work okay on cast. Am I going to wreck the tranny, or do you think this might work?

So, lots of questions. Any ideas on any of them would be appreciated. Also, I think I'll b looking for a winch drive shaft, 1" keyed hole at the front end and 1-1/8" keyed hole at the back end. Not sure if this is standard M37, standard civilian PW, or some hybrid. I don't think I can use the one off of the old gearbox contraption.

By the way, that old rear gearbox is kind of neat. It takes one input and divides it into two outputs, each of which has both a forward, reverse, and neutral position. Its oil is mud too, but it doesn't look too rusty inside. It's a Dana/Spicer 16B. The shifters turn, rather than slide, like an M715 PTO. I don't know what it came off of or what could really use two independent bi-directional outputs, but it has to be good for something special, probably something that we'd do with hydraulics nowadays.



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