Cat 725 Transmission Issues

[Hunter013]

Cat 725 S/N: B1L02639

Operators said on Friday, the truck lost first gear forward. They shut it off, let it sit, and it worked fine the rest of the day. Monday morning they called me saying they lost reverse, but had forward gears. I went out to troubleshoot it in the field. It had a list of codes pertaining to the torque convertor and trans output sensors. If it idled for while, I lost forward gears. I had it brought back to the shop. The lowboy driver said it drove itself up to the ramps, but he lost forward gear right as he hit the ramps. We dragged it into the shop and we started looking at the wire harnesses and sensors and didn't see anything abnormal. I don't necessarily know which codes to start with troubleshooting wise. The truck also got a new trans/chassis ECM about 2 years ago, and a new Engine ECM within a couple months.

The action alarm code is just because it was unplugged for while, and the turbo inlet sensor was unplugged for separate maintenance on the engine.

The trans filter plugged code came on and off for awhile (you can see in the logged event codes). The filter was changed at least twice since it first appeared. Nothing bad was ever found in the oil/ filters.

The only active codes were for the "trans oil temp sensor: (I think) below (possibly above) normal". But it would flicker from active to not when you would use the shifter.

Any suggestions on where to start would be appreciated.

 

[Nige]

They're all Logged Diagnostic Codes/Events. Where are the Active ones.?

By your mention of the transmission temp sensor Active Code that comes and goes whenever the transmission shifter is moved, a wiring fault. Need to know the exact Code (177-03 maybe.?) to identify which wiring is playing up.

Do you have an electrical schematic.?

 

[ahart]

I think I would go after the codes that have the highest number of occurrences over the most hours as these are pretty reliable problems with your machine and should yield results. After I got those ran down, I’d do a transmission fill calibration along with an oil sample draw. You may know this already but 127 is the highest number of occurrences the ECM will count. Actual total could be much higher.

 

[Hunter013]

I checked the active codes again while machine was running,

Diagnostic:
585-2 Transmission Output Speed Sensor #1: Erratic, Intermittent, or incorrect
673-2 Transmission Output Speed Sensor #2: Erratic, Intermittent, or incorrect

Event (Would only come on when put into gear):
E330 (3) Transmission Output Speed Mismatch

I did the procedure for the 585-2 and 673-2. Everything checked out until I had the sensors plugged into the harness and I checked ohms from the signal pins #14 and #17, respectfully, on all power and ground pins in J1 and J2 connectors. Every pin just showed an open loop. Am I missing something? or does this mean something else?

 

[ahart]

Those events typically happen when there’s too much difference between input and output speed, likely something in the transmission has failed.

 

[Nige]

I know you said in the OP that both transmission filters you changed after plugged filter warnings came up didn't have anything significant in them but have you pulled the suction screen & magnetic filter from the transmission for a look.? That would confirm ahart's thoughts as posted above.

 

[Hunter013]

I dropped the filter and oil. Lots of shavings. Something mechanical definitely failed. What would be the next steps?

 

[ahart]

Post pictures. Sounds like you’re going to be pulling the transmission.

 

[Hunter013]

Here's the trans oil plug. I didn't take pics of the shavings in the oil. It all looks like small and large steel shavings.

 

[ahart]

Don’t forget to pull the transmission pump and oil cooler to clean contamination and clean/replace hoses and lines going to and from.

 

[Nige]

Don’t forget to pull and replace the transmission pump and the oil cooler

Fixed that for you..........
We wouldn't contemplate doing a transmission, especially one with that much metal in it, without replacing the pump and the cooler.

 

[ahart]

I agree, replacement is the correct practice.

 

[Hunter013]

I’m assuming there’s nothing else to do/ check, besides rebuilding/replacing the transmission? What’s a typical reason for a trans failure like this?

Any tips on pulling and replacing the tranny?

 

[Nige]

What’s a typical reason for a trans failure like this?

How many operating hours are there on the transmission.? I don't for a minute believe the Diagnostic Clock on the Powertrain ECM.

Any tips on pulling and replacing the tranny?

To pull the transmission, the cab and the belly guards all have to come off first. See attached

 

[Hunter013]

Before the powertrain ECM was replaced, it showed 5959 hours. Now it shows 938. Unless there is some other unaccounted hours, should be 6,897 hours.

Would the E047 - Transmission abuse warning codes create an issue that would make something in the transmission fail?

 

[Nige]

Would the E047 - Transmission abuse warning codes create an issue that would make something in the transmission fail?

With only 7 instances of the Event in 900+ hours on the current ECM I would doubt it.
"This event is recorded when the operator shifts out of or through Neutral with the engine speed above 2000 RPM."
Generally this happens at the dump or the loading area when the operator doesn't allow sufficient time for the RPM to decay before shifting F->R or vice versa.

 

[ahart]

Do you have oil sample analysis reports on the powertrain for this machine?

 

[JD955SC]

I’m assuming there’s nothing else to do/ check, besides rebuilding/replacing the transmission? What’s a typical reason for a trans failure like this?

Any tips on pulling and replacing the tranny?

Before you start slam your hand in the heaviest truck door you have. It’s going to be the least painful part of what’s coming.

I don’t know for sure about the older 725s like the B1L prefix but most of the 700 series articulateds use a tooling group that is basically two uprights with a cross bar, all made of square tubing, to hang a come along from to support the rear of the engine so make one when you get there. Check out your Cat Dealer’s one to see it.