Spring is here and we started the little D4 for the first time in several years. Changed gas and the pony motor fired up , spun the main engine and she fired off as if she had been put away yesterday. Except for the main clutch , that is. I can't get the lever to move [it's in the disengaged position] and it started to smoke so we shut the engine down.

The machine hasn't been used much in the ten years or so that I've had it, basically moving it from one spot to the other, but the clutch has always worked fine so I never paid much attention to it. It has what looks like a fill cup next to the lever on the floor so it might be a wet clutch in need of some oil? I don't want to just yank on the handle until something happens so any advice would be appreciated.

Tend to think you have a rust/sticking problem either with the release collar and main shaft or the rear plate and drive teeth or both. Now partially released allowing the chutch to slip and build heat.

Squirt some of you favorite rust penetrant on these items and try working it after a good soak. A little prying and persuasion ought to free it up.

The cup is to oil the clutch release collar and bearing. Oil every day before operating. An oil clutch will have a dipstick and breather on the compartment.

If the lever won't move, it's probably what's stuck, after all up to the point where it goes into the cluch housing it has been exposed to the elements. That said, the parts inside a clutch housing which has accumulated moisture over the year might be in a worse environment than those outside where it can dry out when the weather is fine. There is a drain in the bottom of the housing to drain any oil and water that has accumulated.

If you wiggle the lever back and forth as much as possible and look inside with a flashlight, you should soon see what is holding what. There should be enough slack in all the joints for the loose parts to move a little

I'm about at wit's end [doesn't take much in my case]. The lever is stuck in the forward [disengaged ] position. Removing the cover , I can see the collar doesn't move in response to the linkage. Weeks of soaking and waiting haven't helped. What do I have to lose by attaching a chain, engaging the tranny [5th gear] and trying to tug it backward to break loose whatever is holding it?

I'm wondering if the clutch could have rusted up so badly it's locked up? Just from the sound of what happened; smoke out of the compartment, maybe it's swollen up enough to push the throwout collar far enough to the rear to engage the clutch brake. I've seen steering clutches rust up so bad that they locked up due to the rust swelling and taking up all the free space, and I see no reason that this couldn't happen with the main clutch.

I think I'd loosen the clutch brake adjustment up first, then loosen the clutch adjustment collar a couple of turns and start lightly tapping the driven disk and see if it frees up. I wouldn't pry the driven plate as there might be a chance of tearing the lining off the clutch disk.

Well, I've stood on my head long enough and played with this stuck clutch off and on for the better part of 6 months now. I think the old girl is waiting me out and knows the price of scrap has dropped dramatically so I won't get her hauled to the breaking yard... I want to try the last idea that suggested loosening the clutch brake collar and thought I had the right bolts figured out but if I do, it's going to take a skinner, more agile person than me to get to 'em. On my 7u [Ser # 24540], I understand I can take the top plates off in two sections to get down to the clutch. I'd like to get a service manual detailing how to do this so if I have to hire it out, I can make sure we do it without damaging parts. Anyone have an idea where to get a service manual for something that old? Haven't found anything on e-bay, Google, etc. but maybe I'm not doing it right. Any thoughts appreciated. If that old gal didn't run so sweet when she was right......

I think there was a service manual on the forsale/wanted ads on this site 2 weeks ago. I think the mans name was Kevin, he had several differnt manuals or just a wanted ad here.

Hartleyboy,
You can get a Cat reproduction manuals from Cat in the Legendary literature. The Serviceman's Reference Book, Operation & Maintenance Manual, Parts book as well as the Diesel Engine book are all available. They run about $50 each as I recall and they're well worth it I feel. The Operation & Maint. manual was less but I can't remember just what it cost, I consider it an owners's manual.

If the collar won't move and soaking and prodding have no effect then it's time to pull the clutch and sort things out.
Attempts at pull starting will have no affect on loosening or moving the collar.

One of the later alterations to the release bearing operation was an extension of the oil lube hole/passage so that oil would get to the collar/shaft interface but early units did not have that feature.

here is one on ebay. Seems to be a good reproduction. cgi.ebay.com/Caterpillar-D4-Tractor-Serv...C293%3A1%7C294%3A100

I have an engine manual for that one but not a tractor one that I'd sell.