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.

 

[TheAutumnWind]

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.

100% do a couple pan drops

 

[01ssreda4]

You have a 60 NOT an 80 and it sounds like its on the way out (worn clutch packs). I would suggest finding a good builder who is fair on price and plan to have it done. Here's my recent swap.

http://www.tahoeyukonforum.com/threads/yukon-down-awd-delete-headers-converter-etc.81191/

 

[Chizzychase]

If you do have the 60e then it probably is on its way to a rebuild. Torque converter is starting to go more then likely causing it to shift hard and have a hard time shifting under harsh load. Mine did the same thing and one day I nailed it to pass someone on the highway and it started smelling like clutch and now it's making a grinding noise and whines as I accelerate. So it's rebuild time for me.
My advice is do a service to it but DONT flush it drop the pan and drain as much out as you can and fill it back up with new atf and a new filter and baby the crap out of it all the while you're saving for a rebuild because it will need one soon

 

[adventurenali92]

The 2003 Denali XL came with the 4L60E not the 4L80E. I'd say save for a rebuild as well. I tried all the simple steps with fluid and such and replaced the solenoid pack and it did nothing to fix the problem so I ended up having my 20p6 4L65E trans rebuilt anyways. Not cheap but well worth the money I spent on it.