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Gary
Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 16758
Experience:  GCM master tech over 25 years
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I bought a 2004 GMC Envoy XL. The truck starts up great, but

Customer Question

I bought a 2004 GMC Envoy XL. The truck starts up great, but when you drive it there's a clunking and I think somethings wrong with the transfer case or tranny. How can I check and are there known issues with this truck?
Submitted: 1 year ago.
Category: GMC
Expert:  Gary replied 1 year ago.

where do you hear the clunk from ? what speed will it make this clunk noise ?

Customer: replied 1 year ago.
I this is the first time I drove it. Just bougth it as is. Started right up put it in drive and it stalled out twice. Started right back up. Pulled out onto the street and it had power but it would speed up and ever 5 mph loss power and rev up a little then it repeated that every 5pmh faster. Got up to 60 mph and turned around. It did the same thing. Reved up from 2000 rpm to 4000 rpm. 2000 when it went faster and then 4000 when it reved up every 5 mph faster. No check engine lights, nut I'm going to hook up my snap on scanner to see if any are stored. 4.2l
Expert:  Gary replied 1 year ago.

see if there are any codes set

if not what gear will it do this is ?

Customer: replied 1 year ago.
It does this in drive 2wd. I haven't attempted to turn on the 4x4 yet. Here are the codes that came up.
Expert:  Gary replied 1 year ago.

i didnt ask about 4WD i asked what speed it will do this

Expert:  Gary replied 1 year ago.

the 128 is a bad thermostat

the 16 is a big problem as that code says the carnk to cam timing is off

that can be caused by low or dirty engine oil or a loose timing chain or the rare chance of the cam actuator phaser

Customer: replied 1 year ago.
do you recommend changing the oil and filter. And also change the thermostat and see what happens?
Expert:  Gary replied 1 year ago.

yes

then see if it still does this

Expert:  Gary replied 1 year ago.

you can always get me back for FREE through this post with any follow up with this question anytime as i do not get credit for my work until you rate us here at Justanswer

Expert:  Gary replied 1 year ago.

how are you making out ?

Customer: replied 1 year ago.
Changing the oil and thermostat today
Expert:  Gary replied 1 year ago.

let me know how it goes

dont forget to rate us here

Customer: replied 1 year ago.
Ok I changed the oil and filter. Then the thermostat. When I pulled it the thermostat was open. That means it was bad right? Stuck open. I drove it down the street and the motor seems strong. But the acceleration problem is still there. Pulled out onto the street and it had power but it would speed up and ever 5 mph loss power and rev up a little then it repeated that every 5pmh faster. Got up to 60 mph and turned around. It did the same thing. Reved up from 2000 rpm to 4000 rpm. 2000 when it went faster and then 4000 when it reved up every 5 mph faster. Now what?
Expert:  Gary replied 1 year ago.

if you clear the codes what code will reset ?

yes that is correct it is not supposed to be stuck open

Customer: replied 1 year ago.
I don't have the scanner at the moment. Friend took it back.
Expert:  Gary replied 1 year ago.

first see if there any codes being set

does it feel like its slipping in and out of gear ?

Customer: replied 1 year ago.
No check engine lights. And no it doesn't feel like its slipping out of gear.
Expert:  Gary replied 1 year ago.

at this point it needs to be driven with a scan tool monitoring live computer data and live transmission data and see what reading is not right when its acting up

Customer: replied 1 year ago.
Aren't there any known issues? I don't have a scanner anymore
Expert:  Gary replied 1 year ago.

just internal transmission failures of the 3-4 clutches

we did not have too many issues with the transfer cases on these trucks

Customer: replied 1 year ago.
Can those be fixed or do I have to have the transmission replaced C