My 2002 Duramax - Down on power, or is it just me?

[TheAmigo]

Everyone,

The history: I've had the truck since new. No mods. I replaced the injectors myself 3 or 4 years ago. ~160,000 miles on it now. It has been a great truck other than for the injector issue. We've had four kids since purchasing it and it holds all 6 of us nicely. It's paid for, and I'd like to keep it for as long as possible.

However, over the course of the last 2 or so years(?) it seems to have lost some of its get-up-and-go at higher speeds. When starting out from a standstill it seems to do just fine up to normal highway speeds.

But:
1.) When going uphill it seems to slow down ever so gently, and then when it finally downshifts it's all show and no go. Noise, but no feeling of acceleration.
2.) At interstate speeds of 60 or 70, when downshifting, it's again all noise but very very little acceleration.
3.) At times it seems that if I >slowly< roll into the accelerator it can increase speed faster than if I put it all the way down to force a downshift.

And, really, I've had it so long and this has been such a slow deterioration (if at all) that I have a had time remembering how things should really be. I just feel that it's not normal.

It throws no codes. And it's not like what I've read here regarding the limp mode.

Any ideas?

Thanks.

[rapidoxidationman]

Any codes?
How's the air filter (can the truck breathe)?
Can you hear the turbo spool up?

When I replaced the head gaskets on my '05 at 130K, the intake manifolds and heads were getting pretty gooey with black fuzz (thanks to the EGR system?). I wonder if that might be happening to yours?

[TheAmigo]

I keep everything clean. No codes. Good air filter. I do hear the turbo. When I replaced the injectors everything inside was clean.

I think I read somewhere else that it could potentially be the transmission slipping at higher revs and just not putting the power(noise) to the wheels?

Any codes?
How's the air filter (can the truck breathe)?
Can you hear the turbo spool up?

When I replaced the head gaskets on my '05 at 130K, the intake manifolds and heads were getting pretty gooey with black fuzz (thanks to the EGR system?). I wonder if that might be happening to yours?

[rapidoxidationman]

You'd see the disconnect between the transmission and wheels on the tachometer. What does the transmission fluid look and smell like? Fresh, clean, red and sweet or brown/black/burned?

[TheAmigo]

What do you mean when you say I'd see the disconnect between transmission and wheels? The tach revs. The engine makes noise because it downshifted, but the truck just doesn't get up and go like I think it should(and used to).

I'll check on the fluid condition but every time I've checked, over time, it has been fine.

You'd see the disconnect between the transmission and wheels on the tachometer. What does the transmission fluid look and smell like? Fresh, clean, red and sweet or brown/black/burned?

[TheAmigo]

Does anyone else think this could be a transmission issue with something slipping under load?