D3B Engine Wiggling and Broke U-joint

[Nick350]

Hello friends,
I recently got a 1985 Cat D3B after a lot of searching. Unknown hours, almost new undercarriage, and a decent amount of blue smoke. (Is that caused by piston blow by?)

Overall it is in pretty good shape but when fixing some minor leaks we noticed the engine was wobbling while running. I have a video below that shows this but while in gear (forward or reverse) the engine has a general wobble and a bigger one while shifting. A little bit after noticing while driving to park it, the ujoint on the output shaft of the transmission sheered while shifting from forward to reverse.

Upon inspection, all 4 engine / tranny mounts are connected but some of the rubber pieces look quite bad. Is worn out rubber enough to cause this much movement? Enough to sheer the joint bolts (pics also attached)?

Thanks for any help
-Nick

 

[Welder Dave]

The mounts are the first thing I'd check and you can get aftermarket motor/tranny. mounts. It's possible the bolt in the middle of the mounts are loose (or missing) or the mounts themselves are loose. It also looks like the big plate around the U-joint attachment is maybe missing some bolts and the bolts still there are quite loose. I can see a gap under the bolt heads.

You'll need to jack the engine up to replace the mounts. I had one of the rubbers deteriorate due to a loose fitting that dripped diesel on the mount. I had a cast iron oil pan installed so could jack on it a little. I loosened the other 3 mounts. If you have a stamped steel oil pan you'll have to figure a way to prevent denting the oil pan when you jack the engine up. You can see the grease fitting for the U-joints.

 

[Nick350]

The mounts are the first thing I'd check and you can get aftermarket motor/tranny. mounts. It's possible the bolt in the middle of the mounts are loose or the mounts themselves are loose. It also looks like the big plate around the U-joint attachment is maybe missing some bolts and the bolts still there are quite loose. I can see a gap under the bolt heads.

You'll need to jack the engine up to replace them. I had one of the rubbers deteriorate due to a loose fitting that dripped diesel on the mount. I had a cast iron oil pan installed so could jack on it a little. I loosened the other 3 mounts. If you have a stamped steel oil pan you'll have to figure a way to prevent denting the oil pan when you jack the engine up. You can see the grease fitting for the U-joints.

Thanks for the response, you are correct that plate was slightly out of alignment and missing a couple bolts.

I wasn’t going to get into but I had the dozer dropped of at the dealer to fix a tranny leak (the seal on the output shaft.) and a blown hardline. Ended up needing a new housing as it was wollered out making the seal go bad. Did this in transit from buying it and appears they didn’t tighten on reinstall.

I am guessing it’s all caused by the motor rocking around and bouncing the shaft around.

The one mount has diesel all over from a leak we just fixed on that side. I’ll check for a grease point on the u joint when I fix it

Thanks for the advice on lifting, I’m planning on replacing all 4 rubbers and I’ll check the mount bolts

 

[Welder Dave]

The mounts aren't greased just the U-joints. Diesel and probably oil too deteriorates the rubber on the mounts. The bad one on mine came out in chunks and some of the rubber was even missing.

 

[Nige]

Best thing you could do if you plan on tackling a lot of this work yourself is to get a shop manual.
Post a Serial number and I'll find out which is the right one for your tractor.

 

[Nick350]

Best thing you could do if you plan on tackling a lot of this work yourself is to get a shop manual.
Post a Serial number and I'll find out which is the right one for your tractor.

I picked up a paper operators manual and bought a pdf for the service manual right after I got the machine

 

[Nige]

bought a pdf for the service manual right after I got the machine

Not one of those $65 memory stick jobbies from eBay I hope.?

 

[Nick350]

No a Jen sales digital copy one, it was $20 and is legit.

 

[Nige]

No a Jen sales digital copy one, it was $20 and is legit.

Jensales manuals don't have the greatest of reputations but if it works for you, have at it......
FYI a genuine OEM service manual sells for around $500 new, or $350 in pdf on a CD.

 

[Nick350]

Update for the thread, I swapped out the front motor mounts and got a new u-joint installed. Motor is rock solid now and the machine is working great.

One of the mounts was completely deteriorated.