Cat 525 grapple skidder transmission issue when hooked to large pull?

This topic contains 3 replies and was last updated by lectrocrew 8 years 11 months ago
October 14th, 2012 6:03am
This transmission is the original with >15,000 hours. It pulls good with medium loads but when hooked to a large load the trans will start to pull/no-pull/pull ect. with about 5 seconds between. This is regardless off whether in 1st or 2nd gear (or 3 or 4, but I rarely pull in 3 and never in 4). It also will stick in reverse gear whether forward is selected or reverse and vise-versa. It will always shift to neutral correctly when selected. Once this issue starts there seems to be nothing to correct it, including complete cool down of the machine. It will return to normal operation at some time (not sure yet what criteria is involved with this return to normal?)

We have replace the $198 transmission direction control switch on the steering wheel but it had no effect on this problem).

My boss is a struggling logger and can't afford the cost of Caterpillar to send a mechanic, but...

One issue that concerns me is that he has been using Shell Rotella/Chevron Delo 400 'motor oil' in this transmission, which leaks ~ a gallon per 40 hours of operation because he says it's cheaper? I don't agree with this but it's his machine and he is hard headed/un-educated on API oil standards...

My main question is if using the improper oil can result in this type of symptom since I disagree with his use of motor oil in the transmission, but any other information is appreciated since I need this machine running so I can have a paycheck.

Thanks a ton for any help!!!

October 14th, 2012 7:55am
Welcome aboard. It's always nice to have new blood.

I'm assuming that this is a manual (as in not electronic) power shift transmission. It is hydraulic, and a hydraulic system would run on water, if necessary. Not for long but it would. The incompressibility of liquids and all that.

The oil you're using should not be a factor of operation unless the machine is exceeding the temperature range, the shear strength range or the oil is worn out due to overuse. Adding a quart a day, it should not be worn out.

We need more info regarding the operating temperatures the tractor is operating at. You need to use a heat gun and check all the points where heat can be generated and be a factor of over-heating: the torque convertor outlet, relief valves, and coolers. Ideally, in the maintenance records for this machine, there would be records of heat levels when everything was working right, so it would be a simple matter of comparison to the temperatures now. I did say ideally.

If the transmission is not overheating, the oil pump may not be able to maintain pressures required to keep the transmission in gear. The pressure could be low causing it to shift in and out, or the oil pump may not be able to output enough oil to keep it engaged.

The next thing your going to have to do is take pressure test readings for the transmission. Get out the manual and find what the pressure readings should be.

The third thing you may have to do is flow checks. this is more difficult and you need the proper equipment.

Associated with the flow is the filters. Are they still serviceable?

When you have more information, come back and see if we can help.
October 16th, 2012 2:42pm
I just remembered that I forgot to mention the SEARCH BOX in the top right corner. Enter key words like: Powershift, Transmissions, Shifting, maybe you can find other information that key help.
October 17th, 2012 5:08am
Thanks Jim!

At this point we have it operating (2 full days now) without any issues after replacing a collapsed orfice tube in the transmission valve body, but I'm only half confident this problem won't come back to bite us again.

The stored codes in the PCM were no help since they have likely not been cleared after years of component failures and repairs. e.g. The following codes existed until I reset the PCM this morning.

'Electromic Transmission / Grapple Control Module 081'











'Caterpillar monitoring System Module 030'










I didn't get a chance to check for fresh codes after I ran it today, but I'll do so 1st thing tomorrow.

And hopefully there will be no codes and there will be no further issue with this transmission malfunction. If so I'll obtain the test equipment you suggested and dig further into this issue.

Thanks so much for your help so far!!!

Reply to: Cat 525 grapple skidder transmission issue when hooked to large pull?