Transmission problems on Cat 518 Skidder

[Don K]

I need some help guys if possible. I have a friend at work that has a 1993 Cat 518 Grapple skidder that has quit moving on him. It has a 3 speed transmission. A little background on events leading up to the problem. He bought the skidder to move timber on his farm. No problems when he got it except leaking seal on blade cylinder.

His son borrowed it one day and checked the oil and found it a little low. He put hyd. fluid in by mistake and then run it app. 5 miles to do a coupla hrs work. On the way back it quit going. My friend drained it empty when he found out his son put hyd. fluid in it. It worked after that but after warming up the oil when using it it hesitates when he shifts gears. A coupla weeks ago he was going to move and it would not move when put in gear. He has tried it a coupla more times with no luck. Does anyone know what might be the problem to help him get this thing fixed and back in use.

Don

[spencerhenry]

not exactly sure what the difference is in hydraulic oil vs hydraulic trans oil. probably anti-foaming. but if the trans was only a little low i doubt topping it off with hydraulic oil would really matter. what kind of trans is it?

[Don K]

To clarify a little. He says that it doesn't use hyd. oil in the transmission but that it uses Delo 400 motor oil. All I know about the trans. type is that it is a 3 speed automatic. Short shift lever with a twist handle for 1st thru 3rd gear and you pull it back to engage reverse in any gear. It is mounted on the column.

[spencerhenry]

sounds like a clark powershift. my forklift has a clark that shifts like that, it uses dexron atf. my franklin has a clark powershift, it currently has hydraulic trans oil in it. my massey ferguson skidder has a powershift of sorts, and it is hydraulic trans oil, my forwarder has a funk powershift, and it uses hydraulic trans oil.
????

[Rob-IL]

Hello; that trans uses Marathon Series 3  straight 30W oil (or equilvent) Just adding Hydraulic one time wouldn't cause any tran problems. Does the winch shaft turn when the engine is running??? There is a screen located in the front and bottem of the trans next to where the front drive shart yoke comes out. That would be a good place to start looking!!! It has several (maybe 6-8) 3/8 bolts. Another thing would be the priorty valve (located at filter housing) could be stuck. Unless your familar with Cat transmissons or really mechanically inclined, you might want to have a Cat man check it out. It might just be something quite simple or then again it could be mega$$$$ Hope this helps!!!

[Don K]

It's been a while but my friend just told me today that the shaft going to the winch is not turning when it runs and he said in the past it always spun when cranked. He has went through a list that the cat mechanic gave him to check, but maybe since I've brought it back to the top maybe a fresh set of eyes might see it and have a tip for him.

Thanks,
Don

[Rob-IL]

You will need to ck your charge pump pressure at the filter housing and (or) regulator to see if the pump is even moving any oil at all!! If the charge pump is moving oil, it could easily be a Torque Converter problem$$$ I have also seen the gear on the output shaft of the converter slide outta place after the retaining bolt breaks. This gear drives the tranny on the bottom side and the winch shaft on the top side. This bolt breakage usually happens from the shock when the operator continiously throws the machine in the opposite direction whithout letting the skidder come to a complete stop. It's just as easy to pull the engine and tranny out together to gain access to the converter and needless to say, it's quite a job$$$$$ I've seen rebuilt converters sell in the $1000-$2000 range.  BUT before you consider pulling it out, make sure a Cat (or experienced) mechanic trouble shoots the problem!!!  Hope this helps!!!

[Don K]

Thanks Rob,

I'll pass this on to him. It might get him started in the right direction.

Don