Trans Shift issues 03 Yukon Xl Denali

[erock198]

I have a 03 Yukon XL Denali with a LQ4 and a 4L80E. For some reason it is not shifting smoothly anymore. It shifts fine if I am soft on the pedal but wont shift if I am ******* it. It was suggested I get the codes out of it. I did but did not save them but I did clear them. I didnt understand the code reader. I hope I can get them again.

I was wondering if anyone had any other ideas before I start throwing parts at it?

 

[Matahoe]

Always start with codes first. Don't throw parts at it thinking that will fix it. The code could point to coolant temp sensor, throttle position or other. In the mean time check the condition of the transmission fluid. My suggest would to have the dealer flush service. This might unstick something. If not then oh well...you got new transmission fluid in it.

But first you want the codes because you might have a solenoid that is bad in the transmission. Would hate to see you replace the fluid two or more times in an attempt to fix the problem.

 

[TheAutumnWind]

Always start with codes first. Don't throw parts at it thinking that will fix it. The code could point to coolant temp sensor, throttle position or other. In the mean time check the condition of the transmission fluid. My suggest would to have the dealer flush service. This might unstick something. If not then oh well...you got new transmission fluid in it.

But first you want the codes because you might have a solenoid that is bad in the transmission. Would hate to see you replace the fluid two or more times in an attempt to fix the problem.

Not a big fan of forced flushes personally. But if you already have problems it might be a decent idea.

 

[TheAutumnWind]

I have a 03 Yukon XL Denali with a LQ4 and a 4L80E. For some reason it is not shifting smoothly anymore. It shifts fine if I am soft on the pedal but wont shift if I am ******* it. It was suggested I get the codes out of it. I did but did not save them but I did clear them. I didnt understand the code reader. I hope I can get them again.

I was wondering if anyone had any other ideas before I start throwing parts at it?

4l80e? Who did the swap? They come from the factory with a 4l65e.

 

[erock198]

I ran the VIN on the mitchell Site and it said I had a 4l80e.

 

[erock198]

I was advised not to do a fluid change after that long 115k because it might lead to other issues or failure nut the fluid is dark. It is the correct level though. I wanted to add that when I hit the trailer tow button it shifts worse.

 

[Rocket Man]

I ran the VIN on the mitchell Site and it said I had a 4l80e.

I thought it was a 4l60e in those? What's your RPO code for the tranny ?

 

[Matahoe]

I was advised not to do a fluid change after that long 115k because it might lead to other issues or failure nut the fluid is dark. It is the correct level though. I wanted to add that when I hit the trailer tow button it shifts worse.

FWIW I have had the transmission flush done with 3 trailblazers and 1 tahoe and 3 suburbans. All with over 150K. If you don't opt for the flush...then just get a pan drop. If you have the deep pan that will replace about 6 or 7 quarts. The end goal is to replace as much fluid as possible. Because fluid level and condition is a main cause of transmission failure.

 

[Rocket Man]

I had the pan dropped on mine to replace the filter and fluid at 130 k and it's doing good 15 k later.

 

[Matahoe]

I had the pan dropped on mine to replace the filter and fluid at 130 k and it's doing good 15 k later.

I usually combine a filter replacement and flush within a year of each other. It's A1 on my list after buying a used vehicle. No matter what the previous owner may have done. I just dont trust those quick oil change bays people often go to.

Same time flush and filter replacement usually costs me about $320. And I have at times immediately started towing my 7500 lb trailer the next day after the service. The transmission shifts the same. I even had them show me the pan to check out the magnet.