So I have a 05 2500hd Duramax with the Allison trans and it has a 4wd issue. Sometimes the 4wd will work or at least I believe it is working, if I don't have the engine on and out the truck in neutral then hit 4h or 4l I can hear the solenoids/motors switching it and I believe the axle disconnect and the transfer case are working, I know the transfer case is working because just going 4h to 4l I can hear it and it seemed to be making noise from 2h to 4h but after driving it around or just switching between 4wd and 2wd a few times I get a service 4wd on the dash and either no lights on the 4x4 switch or the 2h light will be on but nothing happens if I hit the buttons. Curious if anyone knows where exactly is the best spot to start I have already replaced the switch and it does the same thing.
2005 GMC 2500hd lly allison 4wd issue.
- Thread starter MrV
- Start date
Welcome to the forum from Oregon.
If you are in a "salt on the roads" area of Oklahoma, it can pay to remove the encoder/transfer case motor and inspect. Clean and lube where you can and also check for corrosion on the connector.
If you are in a "salt on the roads" area of Oklahoma, it can pay to remove the encoder/transfer case motor and inspect. Clean and lube where you can and also check for corrosion on the connector.
We don't salt our roads here so that is a non issue, I just messed with the truck more and got it to work again consistently so I guess I will have to see if it holds up, I have never been a fan of the electronic 4x4 systems and all my trucks are manual case and manual hubs.
So, you are saying that your 2005 Duramax is a manual case and manual hubs? The 20 years of age, alone, can be a reason to pull the motor and inspect and inspect the connector.
Cadillacmak
Well-Known Member
I am with you on that, I prefer manual also! I am betting the encoder motor needs cleaned and lubed, or replaced like @ORVietVet said. That's where I would start.
No it's the push button 4x4, I will pull the motor and connector next week probably. Is that just somewhere on the transfer case? I know this truck recently had the trans and transfer case replaced before I started working here on it truck only has 250k miles lol.
It looks like this: https://www.rockauto.com/en/moreinfo.php?pk=8136412&cc=1431220&pt=10323&jsn=700
Be sure to look inside when the motor is removed. That area can be cleaned and get fresh lube, too.
Be sure to look inside when the motor is removed. That area can be cleaned and get fresh lube, too.
Is there a preferred type of lube or just something like bearing grease.
Ok so I was able to pull the codes for it and this is what I got, the cluster thing I think was just because the battery got disconnected at some point, truck was in the shop for a couple days after I blew the coolant crossover tube while towing. The 4wd has gotten to the point where sometimes when I start the truck it thinks it is in 4lo even though it's not and other times I have no lights on the switch and other times the 2wd light illuminates but I can't do anything. I did pull the connector for the actuator on the transfer case and cleaned it but I have yet to pull the actuator itself.
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I believe the first thing to inspect for is a ground problem. Then pull the actuator and inspect thoroughly. Need to get a wiring diagram for the codes circuits and see if there is a common ground.
Ok so I cleaned the ground on the body mount on the driver's side a little more thoroughly and got the 4wd to work consistently, it would go 2hi 4hi then 4lo and run back up to 2hi and I drove it around the yard some to confirm the 4x4 was working. Then I went to put it back into 2hi from 4hi and now 4hi is stuck and disconnecting the battery and everything else I'm finding online isn't doing anything. My shift motor has 5 wires which I think is supposed to be the 263 transfer case but I can't find any diagrams for it or diag sequence for testing it.
Pics of the ground connection and any pigtail/eyelet wiring connections there. Need to be sure there is no corrosion creeping up the wire insulation. Are you sure that is the only ground for the system? Did you clear codes and recheck for codes again?
I took a wire wheel on a angle grinder to everything, I haven't not checked for corrosion under the wire insulation and as far as I know that is the only ground for the 4x4 system on these trucks.
The symptoms you describe are classic electrical/ground problems. If the wiring from the ground spot is not corroded inside the insulation and if you follow the wiring to the inside and to the actuator and there is no rub thru of the wires, then the switch or actuator are suspect. I hate shooting the parts cannon at any problem. Your problem is intermittent enough that trying to track voltages and grounds during the problem, is a PITA. IMO, if what I just laid out is all good, then because of the rust build up I see, I suspect the actuator but I would pull that switch and do your best to make the switch malfunction.
I did put a new switch in it because I read all the issues that people had with the solder and one of the lights wasn't working already plus it wasn't that expensive for a dorman switch. I think it may be a communication issue with the tccm communicating with the actuator and maybe that is why it wont even show anything on the switch sometimes. And it's got that TCM power input signal code.
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