Hi all,

This is my first post after having recently discovered this forum. I live out in North East Victoria, Australia.

We have an old RD4 sitting in my back yard...a glorious view from the bedroom window (not)...and we've decided to try and get it going again after many years of it not running.

This one is a 4 cyl diesel crawler, serial 4G 991 W. Not sure what the 'W' signifies, but would be interested to know. From what I understand this serial number makes it quite an early vintage RD4.

It's also fitted with a dozer blade and hydraulics, but this is a later add-on, and does not look like original equipment for this model.

A number of repairs and refurbishments were made when my father acquired it about 30 years ago, mainly to the rollers, steering clutches etc. Not so much to the engine.

It last ran about 10 years ago or more, when it was rather unfortunately was bogged in a paddock. It was left there for a year until things dried out, and then was rescued and towed back to base. It was left in the carport ever since. Well, a year ago we pulled it forwards out of the carport so that we could park our cars there. This required a chain block and tackle. There was so much caked on mud that it would not roll freely...it really was an inch by inch proposition, although the tracks did actually move around.

A friend of mine is a mechanic, with some general experience with tractors etc, so he came down to help me try and get it going last weekend.

We found that the pony motor was stuck engaged with the main engine, and despite our best efforts we could not free it. So we undid the four bolts that hold the whole pony clutch/bendix assembly on to the main body, and tried to remove it. But it would not come out. It wiggles just a little but otherwise seems to be stuck or jammed. We were reluctant to apply too much force in case we broke something.

So then we tried to start it with the pinion still engaged, but the pony gave no sign of wanting to start. And overcoming the additional drag of the main shaft with a rope start is not much fun. At least the whole drive train is not knackered/seized up. (Fortunately there's been plenty of oil left in it the whole time, and the radiator was drained I guess when it was first left in the paddock).

We then decided to remove the pony altogether...at least my friend could take it back to his workshop and try and get it going. He actually managed to do so, after discovering a loose bolt in the magneto that was causing intermittent sparking. It runs as rough as guts, and is as noisy as hell, but at least that's progress.

So our main problem now is that we still need to disengage the pony clutch mechanism. Unfortunately, neither of use can see how to access the critical bit that is jammed/rusted/glugged up. We did manage to take off the handle itself, and from what we can see this part of it is moving freely. We could work the lever back and forth and see that things looked like they were moving correctly. But since we can't seem to pull this whole assembly free from the main body, we're stuck in a quandary as to what to do.

This is where we're hoping someone can advise us!

I do have a set of manuals on its way to me, but I'm not sure if this will answer this question or not.

Looking forward to hearing from anyone who can help.

Cheers,
Milt.

You have to spray some lubrifiant betwen the housing and the pinion cluch after you have to take off the fuel pump governor back cover ,the pinion cluch cover and the screw plate inspection on big motor that should give you room too removed the pinion cluch and if he is not engaging maybe you have to remove the sleeve pinion.

OK Thanks...we did take off the pinion clutch cover - I forgot to mention that - but that on its own did not help us to free up whatever is jammed, which seems to be "deeper" back inside. Will have a look at the governor back cover and the screw plate inspection as you suggest.

Hello and Welcome.
Your 4G993 was produced in 1936. The "W" stand for wide guage track.
On the D4400 engine which you have it is not required to remove the governor back cover to remove starter mechanism...nor does it state that the pinion should be engaged for removal as it does for the later D315 units. They can stick in the housing due to the swelling and rusting of the large sealing "O" ring around the housing. Go easy on prying on the flange as they are cast iron and will break. To release the pinion latches there is a small round plate under the floor boards by your left foot that will give just enough room to bump the release latches. Only need to bump one as they are geared together.

on this and the later one there is no pinion adjusting hole in the housing how mutch tension is suposed to be aplied on the adjusters cutting a hole in the housing would be easr than removing the poney engine

Thanks to Old Magnet and d2dm for your input. The photo and diagram especially helpful.

d2dm: we'd already removed the pony anyway, as it needed some attention in the workshop. But that did not directly help in freeing the pinion.

Also, I think your're right: I don't think there is a removable plate on this unit, but there is a hole in the housing which was either there originally or someone's put it in subsequently. With the help of the diagram and photo I think we can now see what we have to do down the hole.

Will come back with progress report.

I found a really good article at www.vannattabros.com/dozer3.html which filled in a few more blanks.

From what I understand, once the pony is started, you use the pony clutch and the pinion lever to place the pinion gear onto the flywheel, and it latches into position. After this, the main engine is started by opening up the fuel supply. Once the diesel engine catches, according to the article this is supposed to release the latches holding the pinion in position. (I don't really understand how this happens). In any case, does this mean the pinion becomes completely disengaged from the flywheel of its own accord?

And, what happens if you are unable to start the main engine? The pinion is left latched, so how do you release it so that you can repeat the starting sequence some other time? I can see how sticking a screwdriver down the access hole might let me trip the latch, but how do I cause the pinion to withdraw? (Is there supposed to be a spring behind the pinion that pushes it back out of position once the latches are released? Can't see that from the diagram)

Yes, d2dm, you are right about no access on the early D4. Now I remember seeing holes cut in the top cover of the early models. I don't know when Cat added the access hole & cover but it was present starting 7J1. Never have seen a spec on what rpm the pinion should release at. Just words of caution not to let it over speed to much before kicking out. Rule of thumb is each turn of the adjusting screw increases the kick out by 100 - 150 rpm. Also words of caution about noting where the setting is before dismantling. If I had to guess it would be 300 - 500 rpm over the pony high idle speed but that's just a guess.

mctozzy
Tripping the latch dogs has the same effect as having the latches release due to centrifugal force when the main engine starts and overdrives the pinion. The engagement is spring loaded and will release automatically.
Options to start a unit with engaged pinion are to start the main with pinion engaged......manually release the pinion as described........or pull start the tractor and assuming all is healthy with the engagement mechanism it will release on start up of the main. Your understanding of how the starting process works is basically correct.

Well, the old memory hasn't been working to good today. There is a spec for the pinion kick out rpm along with the adjustment instructions.

Well, the old memory hasn't been working to good today. There is a spec for the pinion kick out rpm along with the adjustment instructions.

Also here is a picture of the rest of the clutch/pinion assembly. This is for a 7U model but earlier models are pretty much the same. May confuse more than it helps:D