Hi Guys, been using this forum for a few years to get help with lots of things. It’s been a fantastic help.

I’m based in Brisbane Australia and I have a 2008 Hummer H3 luxury. Recently out of no were my hummer decided to be stuck in 2nd gear. I can select neutral, reverse & drive but regardless if I select drive or manually try to select 1/2/3 it’s just staying in second gear. Motor just revs out with no change. I have no engine lights, no codes coming up on a basic scan tool. But after driving for a while I start to get ABS failure, Traction control Failure etc come up on the screen.

I took the vehicle to a local transmission shop we’re they drove the hummer for a while with a snap on scan tool. They said they picked up a heap of faults and codes but for some reason the car wasn’t producing a engine light or codes, as if it’s ECU wasn’t communicating. There conclusion was there wasn’t anything wrong with the actual transmission & it was most likely the TCM or PCM that had failed. But they couldn’t help me any further.

From there I contacted various mechanics but no one here will work on hummers. So I then researched purchasing a new TCM & realised most don’t come programmed & I’d need to have it programmed by someone for it to work. So I then contacted a bunch of mechanics and auto techs etc but no one can apparently program a hummer here. It’s like a alien vehicle here in Australia. I contacted Holden which is responsible here for GM and they tell me they can’t repair it either, it’s become so frustrating. I do all the repairs on my hummer myself, but there isn’t anything I can do to fix the computers. Failing all that I then tried contacting All computer resources which is located in America as they advertise TCM units that are pre programmed. That sounded promising but during the programming they said there was no such vin for my vehicle. I sent them photos of the vin & bookwork to show it was correct. Then they went from being helpful to sorry we don’t have your part can’t help. So I have no idea what the issue was.

Im at a real loss now, can’t seem to get anyone in Australia to help and have no idea we’re else I could try in the U.S. Hoping someone may be able to provide info on anywhere else in the states that might supply programmed TCM units I could purchase. Failing that does anyone know if I purchased maybe a second hand TCM out of a wrecked hummer the same yr and model as mine, would I be able to plug that in and it possible work?. My poor car is normally my daily driver but she’s been stuck parked up now for 2 months with no fix.

any help would be much appreciated.
Thanks

 

have you checked the wiring going to the transmission? check near the bell housing leading up to the back of the engine. sometimes the wire loom rub through that area. bad motor mounts can cause the loom to rub.

 

I did have a look at the wiring & plugs that I could see or get to going into the transmission & the TCM unit. I also pulled the plugs on the transmission & TCM unit & sprayed them with some electrical cleaner. I’ll get back under there and have a better look and follow them right up to the motor just in case I missed anything.
Thankyou for your reply.

 

Checked all my wiring from the rear to the front and couldn’t find any issues I could see. Also pulled all my plugs going to the transmission etc and cleaned them out with electrical cleaner. Purchased a new PCM & TCM and unfortunately it didn’t change anything. So the transmission shop was wrong about the computers being the issue.

Im thinking it’s definitely something wrong in the transmission itself. Next thing I’m going to try is getting a new transmission filter service kit and dropping & replacing the oil, I guess doesn’t hurt to try. Does anyone have any other ideas as to what to try or look for. She’s still just stuck in 3rd gear, if I’m backing off the accelerator I can sometimes manually select 2nd but that’s about it. Still no engine lights or codes to read unfortunately.

 

Stuck solenoid due to varnish buildup. Add a can of SeaFoam Trans Tune

 

Unless I'm remembering incorrectly, if all you have is reverse, neutral, and 2nd gear, that's a symptom of being in "Limp Mode", which is a self-protection mode to prevent any further damage after the ECU detected a problem. First check the fluid levels: oil, coolant, trans fluid.

You can disconnect the battery for 30 min and reconnect. If it's still in Limp Mode, then it's likely a hard fault.

 

Thanks for the reply, I’m not sure about limp mode would there be a way to know for sure if it is in fact stuck in limp mode?. I don’t have any engine lights, codes or lights or messages coming up on the dash to say that’s the case. Also it’s not restricted as far as speed goes would still do 100km if you let it, it’s just not changing to that next gear automatically or manually. It also hits a bit of a neutral sometimes when you taken your foot of the accelerator and put it back on. I have checked all the fluids are good, I’m going to try replacing the trans filter and put new oil in both the transfer case and transmission. Engine oil was done only recently. The most frustrating part with the car is that it’s not telling me there’s any issues. The abs and system failure message I was getting has gone away since spraying all the sensors and plugs with electrical cleaner, well for now anyway.

 

Clean the shift solenoids ASAP, or wait for it=new/rebuilt 4L60e...tick-tock

 

Thanks Hummerz, I’ll do that when I’m taking off the pan to replace the filter. Any particular way best to clean them?. At this stage prepared to give anything a go, just wish the car would give me some codes so I got some idea where to start. If it keeps going I might just blow it up myself 🤦‍♀️😂

 

That was the case with the vehicle I saw. No lights or reg codes, and you could go as fast as you wanted, if you didn't mind the over-revving.

You're sure there's no 1st gear? In some cases the 1-2 shift is barely noticeable. Because if you have reverse, 1st, 2nd, and no 3rd or 4th/OD, then that could be the notorious and VERY common 3/4 clutch-pak failure that GM never bothered to fix, but someone finally has.