Cat 143h missing gears

[Mason harris]

I have a 143h missing forward 34and 8 reverse 3and6. It all revolves around clutch5 witch is solenoid 7.
Iv got a code 647-6 that flashes on ET 100 time every 5 seconds. Iv checked coils wiring and every thing in between. Are ecm a common problem on these machines.

 

[ahart]

Can you post serial number for machine please?

 

[Nige]

Please post a Serial Number. There are Serial Number breaks in both APN & 1AL prefixes. EDIT: ahart was posting at the same time I was.......
Have you tried switching the complete solenoid valve (not just the coil) to another location on the control valve to see if the problem moves with the valve or stays in the same location.
ECMs are not a common problem. Depending on how may hours the machine has on it you could have a "tired" harness on the transmission control. Long-term heat adversely affects them.

 

[ahart]

Will add that if you have a current above Normal (short to ground) code active, a good test of the ECM is to see if the code will change to a current below normal (open circuit) If a true open circuit is created at the ECM and the code stays active as a current above normal, typically that would indicate an ECM failure.

 

[Mason harris]

Al00505 yes I have swapped the hole valve assembly’s. No change.

 

[ahart]

Please see my last post and report findings. Before you can condemn an ECM, you need to verify whether it’s responding correctly to changes made.

 

[Mason harris]

When I unplug solenoid 7 the above normal code goes away and the open circuit code comes up

 

[Nige]

Al00505

You mean 1AL00505 I assume.?

So when you unplug the solenoid you go from Code 647-6 to 647-5.? If so that would indicate the problem is in the circuit, not the in ECM.
My favourite is still the transmission control valve harness. How many hours are on the machine.? I'll bet the harness is still original and probably over 20 years old. (1AL00505 built Feb 1998.)

 

[Mason harris]

I have Also run wire from ecm to coil 7. bypassing harness. And still same thing.

 

[Nige]

Have you checked for erratic signals from the transmission shifter switch to the ECM.?

 

[Mason harris]

Yes didn’t find anything out of the ordinary. And ET shows gear selection from shifter to be right but actual gear kicks out right after put in gear.

 

[Nige]

And ET shows gear selection from shifter to be right but actual gear kicks out right after put in gear.

Only when you select 3/4/8F & 3/6R I take it.?

 

[Mason harris]

Only when you select 3/4/8F & 3/6R I take it.?

Yes sir

 

[Nige]

I have Also run wire from ecm to coil 7. bypassing harness.

Don't you mean 2 wires.? Solenoid power AND solenoid ground.?
Just for sh1ts & giggles try it with a bypass wire from the ECM to the solenoid for power and ground the other wire from the solenoid to frame ground instead of back to the ECM.

 

[Mason harris]

I didn’t run ground back to the ecm 3 others solenoids share that wire and the other 3 are working fine. I will try the solenoids ground to frame ground tomorrow.

 

[Nige]

I never asked if you had the electrical schematic although it sounds as though you do. If you don't you're welcome to a copy, just ask..

 

[Nige]

I didn’t run ground back to the ecm 3 others solenoids share that wire and the other 3 are working fine.

I agree. The schematic shows 2 ground wires numbered 921-WH, one for solenoids 1/2/3/8 and the other for solenoids 4 thru 7.

A thought. The two solenoid ground wires are both shown as being spliced inside the transmission control valve harness as shown below. Is there any chnace that the splice in 921-WH from #7 solenoid return (arrowed) is showing continuity on a meter but is not up to the job of carrying the current necessary to operate the solenoid and is breaking down under load.?

 

[Mason harris]

It sure could be. Would that throw a currant above normal code ?

 

[Nige]

It sure could be. Would that throw a currant above normal code ?

From what I know I think it's a distinct possibility. The thing is the 4 return wires are not common for their full length. Each of them is dependent to some extent on that splice somewhere in the harness, and I have no idea exactly where it is located.
I'd like to hear an opinion from @ahart

EDIT: That was also the reason for my earlier question regarding how many total hours were on the machine and whether or not the control valve wiring harness was still original. FWIW all our transmission overhaul kits contained a new wiring harness for the control valve.

 

[Mason harris]

11267hr they had the motor out about 8000 hours they said they did All harnesses in rear of machine.