JD crawler

In a word: Yes.

The M is quite a bit different from an A or a B. First off, the 2-cyl engine is vertical, not horizontal. This means that the main clutch and transmission are similar to a car or truck, and quite a bit different from those used in the horizontal engined machines.

Not that you couldn't figure all that out, of course. If you're up for rebuilding A/B bits, you can tackle the M bits. Probably with ease, too. Everything is quite a bit smaller and lighter.

Now, we get into the crawler specific parts. These are a lot different from their wheeled counterparts.

The MC is exactly like an M wheel tractor until you get to the differential. Crawlers have no differential - just the ring and pinion gears. That's the easy part, though.

The hard part comes next, in the final drives. The JD's have multi-plate dry clutch packs. One on each side that allow the power to be removed from the respective track. Then, there are band brakes wrapped around the outside of each clutch pack assembly. These are what stop the tracks of the machine, both when each steering lever is pulled as well as when the master brake pedal is pressed.

Where are all these new and different bits? Stuffed inside the final drive housings, that's where. You have to drop each track on the ground (which is accomplished by driving out the one 'master pin' in each track chain and dropping the things on your feet...).Then, you get to pull off the entire final drive unit to access the clutch packs.

And access them you must. It's rare indeed to come across an older JD crawler that doesn't need to have the clutch packs and brake bands rebuilt. Don't ignore the the final drive output shaft bearings, either, as they tend to take a beating.

You then can pay attention to the rollers. Fortunately, the MC has only three per side (the 40 had 4 and the 420/30/40's had 5 as an option). They are what the track carriage rides on when the tracks lie on the ground. If you look closely bewteen the downside track chain and the main carriage itself, you can see them peeking at you.

Genrally, these never get greased often enough, and the lubricant runs out. The seals are backwards, you see, they are designed to keep dirt out but also let the lube out as well. They need to be greased every few hours of use, and we all know how well things like *that* go. They're fun to get to, being all the way at the bottom like that....

Next, you need to deal with the front idler (that's the front-wheel looking thing). With the tracks off, this one is a piece of cake.

Finally, you have to deal with the tracks themselves. They have hardened pins and bushings at each chain joint. They are not lubricated, so they do wear. Usually, they need to be replaced on old machines. This needs to be done at a specialty shop that has the large presses which are necessary. You can't do those on your own.

You can tell if the pins and bushings are in trouble by looking at the adjustment of the front idler coupled with the amount of sag in the up side of the tracks.

You do need to obtain the JD 'M' service manual before you start this project. It goes into detail of how to tell when things need service, and how to go about doing it all. The usual IT type manuals are worthless when dealing with the crawler models.

If you're lucky, grandpa took care of the little MC and you might get to escape rebuilding the final drives, undercarriage and the tracks themselves. We can all hope that is the case.

Oh, if this crawler has a bulldozer attached, drop off at least the blade before you start. It's a pain to keep bumping into those as you work!

You get spared one thing with the MC: No direction reverser to rebuild. They weren't offered as an option until the 420 series came out.

Take care,

Stan

Proud owner of my late father's 1958 420C crawler w/ model 62 dozer and direction reverser.

Having recently become interested in owning a 40C (when I find just the right one), I'm saving your post as a very worthy check list of what to look for and consider when looking at prospects.

With your apparent insight, you might consider expanding your thoughts into pamphlet form for novices. This could be very saleable. Just because a man might know old John Deere wheel tractors doesn't mean he's, at all, knowledgeable in crawlers.

Thanks sharing your experience.

Putt Putt

Well, all of you are welcome to whatever I happen to know, of course. I'm not the real expert, though. My dad was the crawler guru in the family JD dealership. Since he's passed on, I'll have to stand in for him based on all the hours I spent working alongside him as his helper.

I was the 'kid mechanic' that no one had to pay, you know.:-) As in: "Here's a nice steam cleaner. There's a broken manure spreader. You know what to do."

I suppose I could make something up. There's a wealth of data in the JD service manuals for the M/40/420, etc. That's really what folks interested in crawlers need to read first. JD was always great for taking wonderful photos of a mechanic showing how things were supposed to be.

Maybe I can get permission from JD to use some of that in a 'what to look for in old machines' web publication. That would be the best and easiest way to deal with it. Otherwise, I'd have to re-create all that by tearing into a crawler myself. Well, that might not be so bad, though. I'd not mind having another crawler..... :-)

My wife might not think I need another one, though! :-) :-)

Stan