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AZTechBrian
AZTechBrian, ASE Certified Technician
Category: GMC
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I have a 2003 Yukon Denali. The temperature gauge in the

Customer Question

I have a 2003 Yukon Denali. The temperature gauge in the lower left corner of the instrument display, no longer registers a temperature. I believe this gauge is for the transmission fluid temperature??In addition to the temp gauge not working, I noticed the transmission is not changing gears like it normally would at certain speeds. The vehicle revs higher than normal before shifting into second gear.Furthermore, I am low on transmission fluid. I checked it while the engine was running and the level is at the "cold" line.) so I will add more fluid.But I need to know the location of the transmission fluid temperature sensor, and instructions for replacing it, to see if that is why the gauge is not working.I also need to know if the 'shifting' issue is related to the temperature sensor/gauge not working, or if it related just to the trans fluid being low.
Submitted: 11 months ago.
Category: GMC
Expert:  AZTechBrian replied 11 months ago.

Hello. Is your Denali a 2 or***** and what engine is in it? I will see if I can get the information your looking for.

Customer: replied 11 months ago.
All wheel drive. 6liter v-8
Expert:  AZTechBrian replied 11 months ago.

Ok. 1500, or 2500?

Customer: replied 11 months ago.
I think the problem was just low transmission fluid. After filling it up the temperature gauge is working. I guess I was just severely low on fluid. I hope the transmission shifting problem goes away too.
Expert:  AZTechBrian replied 11 months ago.

the shifting problem is most likely the result of low fluid. The temperature sending unit is located higher up in the transmission, so if the fluid was low enough, there wouldn't be enough fluid surrounding the sending unit to give an accurate reading. I have attached a picture with it's location. Item 34.

https://www.dropbox.com/s/7tlju7bonw3odly/tts.jpg?dl=0

Expert:  AZTechBrian replied 11 months ago.

sorry that picture wasn't very good. here's a better one

https://www.dropbox.com/s/383y2xd3s0fwy52/f.jpg?dl=0

Customer: replied 11 months ago.
I added almost 2 pints of transmission fluid. The temperature gauge is registering a temp after driving around for twenty + minutes. However the vehicle isn't shifting gears like it normally does. Does the computer need to be reset or something? It stays in all the gears way too long before changing gears.
Expert:  AZTechBrian replied 11 months ago.

Hopefully there wasn't any internal damage done. Does it eventually shift through all the gears, but just takes a while before shifting? Are you able to get a scan tool and check for transmission codes? I am reasonably certain that there are codes and they would help us greatly if you can get them..

Customer: replied 11 months ago.
I haven't tried keeping the accelerator down to see if it shifts from 1 to 2 all on its own. When it revs to high in first gear, I take my foot off the accelerator for a quick second, and then it shifts into second. Shifting from second to third seems a bit better. it's hard to tell on the freeway what gear it's in, but at 65mph the rpm is between 2500 and 3000.
Expert:  AZTechBrian replied 11 months ago.

Ok. It sounds like what you have is delayed shifts. It would be great to have the codes, but you may need your valve body reconditioned. This was a fairly common problem with your Denali and GM did provide instructions for reconditioning these valve bodies. There is also a TSB for it

Customer: replied 11 months ago.
I have a scanner that reads codes from the obd2 port but there are no codes. is that the scanner I need to read transmission codes?Also is recondidtioning those valve bodies something I can do or do I need to see a transmission mechanic like aamco?
Expert:  AZTechBrian replied 11 months ago.

You would get the codes from the OBDII port but your scan tool would need to be capable of reading transmission codes. I will attach a copy of the TSB with the information that covers among other things, a delayed shift condition.

https://www.dropbox.com/s/qozggm1yajohm0f/TSB.pdf?dl=0

Customer: replied 11 months ago.
Does that document apply to Yukon Denali non XL? Mine isn't an XL.
Expert:  AZTechBrian replied 11 months ago.

It's the same transmission either way, but isn't your denali a 1500? (half ton)

Customer: replied 11 months ago.
I'm not sure how I know if its a 1500 or not. I know its a V8 6.0L engine. Under the hood it has Vortec 6000 on plastic engine cover. In the TSB, are those the codes I would expect to receive from a delayed start problem?
Expert:  AZTechBrian replied 11 months ago.

It must be a 2500. The 1500 with the 6.0 was only availabe in XL. Anyway, thats not important. When you say delayed start, do you mean you give it the gas when it's cold and the motor just revs?

Customer: replied 11 months ago.
oops...my bad. I meant to type delayed "shift". those words I think best describe what its like to drive the vehicle.
Expert:  AZTechBrian replied 11 months ago.

You wouldn't necessarily get all those codes listen in the TSB for a delayed shift issue. You could have some of those codes or symptoms or a combination of them.

Customer: replied 11 months ago.
The odb2 scanner I have says it reads all power train codes for any make and model after 1994. Would the codes in TSB make the check engine light come on? Regardless my scanner is reading 0 codes and the check engine light is not on
Expert:  AZTechBrian replied 11 months ago.

In most cases a power train code will illuminate the light. Not always but usually. Regardless of whether or not there are stored codes, we do know that you have a transmission problem as delayed shifting is not normal. Delayed shifting is usually caused by sticking valves in the valve body, and it so happens that your transmission's valve body was prone to problems to the point that a TSB was issued for it. Even though your not finding any codes, I would perform that TSB.

Expert:  AZTechBrian replied 11 months ago.

If the computer doesn't recognize the issue, a code won't be stored. We see vehicles every so often that have a clear problem, misfires, etc.. and no CEL (check engine light). It just makes it a little more difficult to find the problem when that happens..

Customer: replied 11 months ago.
What do you think about the theory that the 2-4 band broke. so rather than a "delayed" shifting, its actually a shift from 1-3 because the 2-4 band broke? This is what a local transmission shop says is more likely the problem than a sticky valve. I drove the vehicle on the freeway and it doesn't seem to shift into 4th gear. Driving on regular streets does seem to shift from 1-3 and miss the second gear.
Expert:  AZTechBrian replied 11 months ago.

Woah, that's a bit of a twist.. Based on that last reply, I would be pretty confident that there is internal transmission damage. This no longer sounds like a simple delayed shift condition that does shift through all the gears.

Expert:  AZTechBrian replied 11 months ago.

skipping over second is exactly what would happen too if your 2-4 band broke

Customer: replied 11 months ago.
I drove it today and paid closer attention to the shifting and it definitely seems to only hit two gears. if the 2-4 band is broke, how much should I expect to pay to fix? Is the "2-4 band break" the definition of a transmission rebuild? the local transmission expert says at most it would cost $2400 to replace/rebuild, or if the 2-4 band can be replaced it would be only $1200. To determine the cost he says he must drop the transmission pan to see if the band break caused other damage.
Expert:  AZTechBrian replied 11 months ago.

The 2-4 brake band is roughly a 10 hour job. The transmission must be removed to replace it. The 2-4 band is removed toward the beginning of the disassembly process, but it's a good idea to replace the clutches either way. He would have to remove the pan to see the 2/4 brake band to make a determination as to the extent of the damage, as he has said.

Expert:  AZTechBrian replied 11 months ago.

OH, I'm sorry I didn't answer your first question... The 2-4 brake band doesn't define a transmission overhaul. There's a lot more to an overhaul than that band. Much more dissassembly and reassembly and many more parts. Overhaul is a 15 hour job. ( including removal and installation of the transmission)

Expert:  AZTechBrian replied 11 months ago.

was it a broken 2-4 band?

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