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2007 H2 SUT won't shift into high gear. Please advice/help

maddogg

Probationary Member
Messages
3
Location
Houston
Houston, we have a problem!

I have an 2007 H2 SUT with~ 80K miles that I have own for about a year. It has been running fine untill about a week ago when it just would not shift past 3rd gear. It also has trouble shift from second to third also. To reach 60 mph, the engine RPM is almost 5K. AFAIK, there has been no modification or tuning done to the engine. Since I am not remotely anywhere as knowledgeable as a mechanic, I have no idea what's going on. Please help. Thanks in advance.
 
Last edited:

Zach

Mall Crawler
Messages
4,812
Location
So Cal
Check engine light on? Could be as easy as just shift solenoids. You have a 1-2 and a 3-4 solenoid. Have replaced both of mine for it not going into first. Then again hard to tell with just what you have explained. Try hitting an auto parts store or at worst case a dealer to see if there is any codes stored. I know AAMCO's used to advertise running codes for free. Not sure if they still do that
 

maddogg

Probationary Member
Messages
3
Location
Houston
Check engine light not on. Thanks for the advice. I will take it to the dealer since I don't even know where the solenoid are.
 

Zach

Mall Crawler
Messages
4,812
Location
So Cal
They are in the trans on the valve body. Once you drop the pan, they are above the filter. Could be some codes stored and not throw the light. Have had it happen before
 

DaveK

Well-Known Member
Messages
67
Location
So Cal
Check your speed sensor, located, as I recall, on top of the transmission (or it is on my 03).
 

The_Mountain

Well-Known Member
Messages
109
Location
Cow Hampshire
Hey just wanted to know if you ever figured out what the problem was with you hummer not shifting right? Mines doing the exact same thing

I hate to point this out, but this thread is the sum total of maddogg's participation on this board. He never posted again anywhere after that reply telling us he'd let us know what he found, so he's probably never going to see your question.

Did your problem happen all at once, or did it develop gradually i.e. there was a period where it worked sometimes and not others, or there was a particular speed where it seemed to have trouble staying in 4th, or something similar?

I ask because I am also seeing odd behavior from my '05's transmission, or at least I believe it's transmission-related: At around 43-47 mph it feels as though the torque converter doesn't want to lock up properly, and this gets worse when the trans temp gets up around 200 degrees. When it's fully hot, the behavior can occur at speeds from around 37-38 up to over 50mph. I have also noticed that the trans sometimes has trouble fully shifting into gear from park, where I'll shift, I'll feel it engage, but when I step on the gas it hesitates for a second, moves sluggishly, then something happens that feels like it fully connects up and then it works normally. I'm really concerned that I'm going to have to have the damn thing rebuilt or I'll have to buy a reman unit and swap, and that's a big chunk of money.
 

flyday58

Active Member
Messages
27
Location
Ole Miss
Mine doing similar, another forum says it's characteristic of the torque converters used on the 4L6x's in the earlier trucks. Guy on the same forum changed his for other reasons and says shifts are crisper, better acceleration, less hunting.
 

Cardodger

Member
Messages
6
Location
Denver
WOW, here it is 2020 and now my 2007 SUT is doing the same thing. It feels like I only have 1st and 4th gear. I wish he would have posted what was the fix. I am going to try to read the code but if anything I need to change the fluid anyways. So I might as well change the solenoids.
 

Zach

Mall Crawler
Messages
4,812
Location
So Cal
WOW, here it is 2020 and now my 2007 SUT is doing the same thing. It feels like I only have 1st and 4th gear. I wish he would have posted what was the fix. I am going to try to read the code but if anything I need to change the fluid anyways. So I might as well change the solenoids.

Yup! 2020, pretty soon 2021, well few months. Love raising dead posts.

But, seriously, post number 10 if you are experiencing all the same issues. Replace the trans and call it a day. I had the torque converter shutter at different speeds. Then, trans temp spiked. And smoked the trans. With the year and probably mileage you have. Trying to patch it or chase it will cost you more in the long run
 
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