CAT 977L Torque Converter Leak and Milky Fluid

[jezow2010]

Hey Guys,

We have been making steady progress with the two 977Ls that we bought for scrap. We got the one motor free, put the head on from the other machine with the bad bottom end, and actually got it started. Seems to run pretty well.

Immediately it started pouring fluid out of the TC that was white and milky. It looked like from the output flange seal.

From what I can tell or read it sounds like this is a result of it being over full because the engine coolant to trans fluid heat exchanger on the engine is leaking coolant into the trans fluid? Luckily I have a K machine motor and TC on a trailer in my driveway with some pictures attached here. I am pointing at the heat exchanger in question. You could clearly see with the layout of the hoses where the fluid goes from the TC through the heat exchanger up to the oil cooler next to the radiator and then back.

Just wanted to get some thoughts and make sure I am on the right path? Also, why would this happen? Does the heat exchanger corrode and start to leak or is there seals in there or something that goes bad?

Second, is this possibly why it is leaking so bad?

Thanks!!!

Tyler

 

[jezow2010]

Serial on the machine is 11K07393

 

[jezow2010]

More pictures

 

[Nige]

Have you checked for the presence of oil in the radiator.?

 

[361brock]

Check the small drive shaft between the converter and bevel gear compartment. When there is excessive bearing where in rear case the drive shaft walks back and allows the converter to spill fluid which may be aerated and appear milky. If you put your hands on the shaft and are able to slide it both ways with lots of slop, you may have found your problem. My 2 cents.

Nick

 

[jezow2010]

There is no oil in the radiator and the level hasn't really gone down since we filled it although it has just been sitting not running at all. The dipstick on the trans shows milky watery fluid.

Currently there is no driveshaft in it but that could be it although the dipstick doesn't really make me feel like it is.

I think we are going to start it one more time, verify where the leak is coming from and then start draining fluid to see what is really in it.

 

[361brock]

No driveshaft? and oil isn't leaking out of convertor while running?

 

[jezow2010]

The driveshaft isn’t between the yoke on the trans and torque converter but there’s still a yoke in both sides to plug the hole if you will

 

[361brock]

It's between the converter and bevel gear compartment not converter and and trans.

 

[jezow2010]

Nick,

I see what you are saying now. We tore into it and the metal sealing ring on the torque converter shaft was broken and the rubber seal was completely blown out of the hole. We replaced the seal and the ring and put everything back together with the driveshaft and moved the driveshaft to the front of the machine. Started it and no leaks but when we revved it the pressure increased and blew both yokes and the driveshaft back as far into the trans as it could have which caused the metal sealing ring in the torque converter to slide far enough back out of the sealing bore. Then that stopped sealing as a result and put all of the pressure on the rubber lip seal in the output of the TC and that blew straight out. Now we know what the PO was dealing with.

When we got into it there was no seal in the trans and no yoke. I see in the parts diagram/service manual there is supposed to be a spacer on the end of the shaft but I have not checked to see if it is there or not yet. This assembly has about 1/2" of end play in it. I think the end play in the trans sets the whole driveshaft position and like it was said, if there is too much it will slide too far back and blow out the TC seals.

We checked the other machine and it has maybe 1/8" of endplay in the driveshaft/both yokes assembly. Seems like this is how it is supposed to be.

Question is - what causes this slop in the trans. Bad bearings? Time for a new trans? Missing spacer?

attached some pics for documentation

 

[361brock]

Have a chat with you local Cat dealer. They know of this problem and had a temporary fix that involved making the yoke or drive shaft a little longer than spec. This took up the slack or wear on the bearing in bevel gear compartment. I have done this 2x with 977Ks and it works. You will be able to use the machine for years. A good machine shop could it with the right measurements, they cut a new yoke in half and add a small extension and weld it all back together. Back in the day, Cat would have them made up on the shelf it happened so often.

Nick

 

[jezow2010]

I can handle that fix if that is an acceptable fix no problem.

Any ideas as to why there is the slop?

 

[jezow2010]

Hey Nick, is it normal for the input shaft on the trans to have some slop side to side in it? Not just endplay?

 

[361brock]

Side to side doesn't sound good. We are talking about the short shaft made up of a large universal joint and input shaft on either end? The whole thing isn't more than 6 to 8 inches long.

Nick

 

[jezow2010]

I am talking about the input yoke to the trans. Pics attached.

Dove into it more today and the roller bearing that supports the shaft and is the outermost bearing is just completely gone. You can see the races but no rollers in the close up picture. Guess the trans was bad and caused all of this. Now we know for sure why the previous owners parked it!!

Pulling a trans next