shifting issues in 04 Tahoe

[03GMCYukonXL]

Ok so I have a 2004 Tahoe Z71. So here is the story. It shifted fine but had some clogged cats and a knock sensor code. It had no acceleration and could barley make it up a steep hill. I replaced the knock sensors and the cats. It drove ok and then it just started revving ALLLL the way up to 6k rpms in first unless you let off the gas. If you let off the gas, it'll shift to second but always puts it at around 2k rpms. It won't go past 2,200 rpms in second but pulls just fine. Even going up a hill. It want's to shift back to first at lower speeds. It acts fine otherwise. If I'm doing highway driving it acts fine.

Now if I stay at low speeds, like 3k rpms or lower, the truck will shift into 2nd gear just fine. It's only when I gun it that I have to let off. I thought maybe the knock sensor was preventing it from going over 2,200 rpms in second or maybe there is a reset. However that is not the case. I'm thinking about trying to change the shift solenoids. I'm here to get any other opinions on what this may be. It really doesn't seem like the transmission at all. It showed no signs of slippage or anything irregular whatsoever before this.

 

[Rocket Man]

Let’s see the DTC’’s it has. There has to be some codes thrown.

 

[03GMCYukonXL]

Let’s see the DTC’’s it has. There has to be some codes thrown.

None at all. Funny enough

 

[Fless]

You might need an advanced scanner to see the codes; a generic code reader may not see them.

What is the age and condition/color of the transmission fluid, and is the level correct on the dipstick when it's been warmed up?

 

[03GMCYukonXL]

You might need an advanced scanner to see the codes; a generic code reader may not see them.

What is the age and condition/color of the transmission fluid, and is the level correct on the dipstick when it's been warmed up?

It's the original transmission with around $202,000 MI. Not sure if the fluids ever been changed but I already have the shift solenoids, the the transmission fluid, and the gasket. So I'm thinking to just go ahead and change the solenoids and see how that does.

But for what it's worth the fluid level is correct and it is red

 

[rockola1971]

It's the original transmission with around $202,000 MI. Not sure if the fluids ever been changed but I already have the shift solenoids, the the transmission fluid, and the gasket. So I'm thinking to just go ahead and change the solenoids and see how that does.

But for what it's worth the fluid level is correct and it is red

Is it red or is red/orange to orange? Does it stink? Smell burnt? All this RPM's climbing while going from 1-2 sure sounds like clutches slipping like a SOB or your 2-4 band is toasted. If the band is roasted, you'll see its friction material layed out in the pan. It will be obvious.

 

[03GMCYukonXL]

Is it red or is red/orange to orange? Does it stink? Smell burnt? All this RPM's climbing while going from 1-2 sure sounds like clutches slipping like a SOB or your 2-4 band is toasted. If the band is roasted, you'll see its friction material layed out in the pan. It will be obvious

It doesn't smell at all. I have a Yukon that absolutely slips and this doesn't feel like slippage at all. It really seems electronic. I've been reading and it's starting to sound maybe like a faulty TPS. I have a good one and I may just swap it out and see if that helps. I really had no clue the TPS could even affect shifting like that. The strangest part is it's not throwing a code. I hooked it up to my HP Tuners and there are no transmission codes either.

 

[NickTransmissions]

It doesn't smell at all. I have a Yukon that absolutely slips and this doesn't feel like slippage at all. It really seems electronic. I've been reading and it's starting to sound maybe like a faulty TPS. I have a good one and I may just swap it out and see if that helps. I really had no clue the TPS could even affect shifting like that. The strangest part is it's not throwing a code. I hooked it up to my HP Tuners and there are no transmission codes either.

Could be TPS, they go bad and sometimes wont trigger any DTCs. That said, having to let off the throttle to make it shift typically indicates a mechanical problem somewhere in the apply circuit or worn applied elements. Yours sounds like it could be a pressure loss due to a minor leak/x leak somewhere in the 2nd gear apply circuit. Could be at the servo, 1-2 accumulator piston, worn accumulator reg valve, between the vb, spacer plate and case or elsewhere.

Plug in a bidirectional scan tool, bring up live engine and transmission data then take for a drive - see if you can spot anything anomalous. If nothing jumps out, drop the pan and see what's at the bottom. If a bunch of burnt clutch material and/or metal is present, yank it out for overhaul.