Transmission Issues - 2WD Tahoe??
 

Hello All-

Well I had last reported 18K miles in about 7 months (mainly highway) with ZERO issues. In the last few weeks I ran into an interesting issue (3 times) when I shift from reverse to drive the car hesitates or does not move at all for 2 to 5 seconds and then starts moving. I did not consider it a big deal but mentioned it to my Chevy dealer during my routine oil change on Wed. The dealer came back and said there is something up with the transmission but they don't know what and they are VERY cryptic in their explanation. To be honest, it has been a little frustrating and I don't feel I can get a straight answer. The best feedback I can get is they are "consulting with GM on the transmission" and will get back to me. My dealer has told me their mechanics have a hard time with "the hybrid stuff".

So I am on day 3 without my Tahoe and will now hope she gets released on Monday as I have to get on the road again for work!! So - probably too much info here - AND would appreciate hearing any experience anyone has had around the issue described above. I am hoping this is not a big deal - as I perceived when I mentioned the issue on Wed.

Re: Transmission Issues - 2WD Tahoe??
 

the dealers have only one(if at all) tech for the hybrid. nothing gets done unless corporate says it is okay to release the vehicle. reprogramming, software updates, etc. are all done through corporate GM that is why even the dealer's tech cannot say an okay unless approved by corporate. it is probably just a software update/download.

Re: Transmission Issues - 2WD Tahoe??
 

I am not sure about GM Corporate calling all the shots. I am sure they are involved, however more like the Tech guys calling the shots. At my dealership which is in a small town they have two Hybrid trained mechanics that seem to know the vehicle well, they have had the training, and have the equipment, they also seem very dedicated and if they do not have the answere they get it for me.

Re: Transmission Issues - 2WD Tahoe??
 

Thanks for the feedback. The service rep keeps telling me they can't do anything without GM's approval and sign off.

Re: Transmission Issues - 2WD Tahoe??
 

^ this is the same in my dealership when I had them install the motion anti-shock sensor/anti-carjack module.



http://www.gmaccessorieszone.com/Cad...1%5Btype%5D=gm

Re: Transmission Issues - 2WD Tahoe??
 

Another update in hopes my experience may help someone else down the road. I am on day 6 of being without my Tahoe Hybrid, wah. Got in touch with Director of Service Dept. He got involved in my vehicle and told me in the afternoon they were waiting on a "download" from GM to update my Tahoe and hopefully fix the hesitation when I hit the "gas" or actually electric. He then called me back at 7pm saying they found that something in the AC unit is causing this (AC works fine) hesitation and the part is coming from Lansing to arrive Friday. By his estimate I probably won't have my Tahoe for another week! Next Monday will be 13 days! Ouch! Hopefully the details of what was found wrong will help someone who might experience this.

Re: Transmission Issues - 2WD Tahoe??
 

Hi Kip,
Thanks for the information and keeping us updated. Interesting. Not fun being without the Tahoe Hybrid for so long.

Re: Transmission Issues - 2WD Tahoe??
 

Hi Kipper,

Can you provide any updates to your situation with the vehicle hesitation? I have a 2008 Hybrid Yukon experiencing the same thing. It's very difficult to replicate the problem, so the dealers are having trouble diagnosing it. They've performed updates, replaced a transmission harness and the auxillary transmission pump, but nothing seems to work so far. I'm curious about your AC unit comment. My truck only seems to do this when it's hot out (I live in AZ, so this is fairly common), as I haven't had problems in the cooler months.

Anyway, thanks for any info or updates you could provide.

Re: Transmission Issues - 2WD Tahoe??
 

Kipper, Not sure why the A/C compressor would cause rev-drive hesitation. I would be more suspicious of a clutch slipping or an aux pump issue. A simple thing to check, is your trans fluid level correct?

kecusc, sounds like you have a different issue. Something in your system is power-limiting due to AZ summer heat. It's either the motor, the power inverter or the battery pack. The Tech2 can monitor key temps in all these areas. One simple thing to check; is your power electronics coolant tank full? It looks just like the regular coolant reservoir and the two are right beside each other behind the radiator. It's a dedicated loop to cool the power electronics. You'll see inlet and exit hoses attached to the lower front of the power inverter module in the rear passenger side of the engine bay. If the coolant level is low, or if there's a blockage, it can limit cooling capacity. But if it's severe there should be overtemp codes recorded in memory.

Re: Transmission Issues - 2WD Tahoe??
 

Hi KC,

Well my Yukon is back in the shop for the same problems as noted before. I checked the electronics coolant tank and it appears to be full, although I can't say whether there is a blockage or not. Last time I was there, the tech drove around with me for a while trying to get it to reproduce, but of course it wouldn't. He had the Tech2 hooked up and said everything was looking fine. I did ask about the 300V batteries and the possibility of a bad cell or something, and he said he had checked the batteries and all was clear. The power limiting idea seems to make sense, although because it is intermittent, the dealer is having trouble diagnosing the problem. I have contacted GM to file a complaint and they are looking into the issue to see what they can do. I will keep you posted. I'm beginning to think that something is wrong with the Battery Pack that causes problems at high temps and after repeated driving. It only seems to malfunction this way after it has been driven for a bit, sits for a while then driven again. It's as if the batteries were drained from the driving, AC use, temp, etc then never recharged properly before the car is parked. Then when driving it again, the batteries just can't keep up until they are recharged.

I bought the car new in July 2009 but it's a 2008 model built in 02/08. The problems started appearing late summer in 2009, went away when the weather cooled over the fall, winter and spring, then started up again this summer.

Anyway, Thanks for the help. As I mentioned, it's back at the dealer now to look into the problem. There's also some new problems now with the fuel gauge and oil gauge fluctuating that have occurred since they worked on it last time. I'm not sure if they are related, but I'm having nothing but trouble lately with this one.

Patrick