Won't up shift

[chzball]

I have a 2001 silverado 5.3 4x4. 195,000 mi. Recently replaced fuel pump.

At wot it will not transition into next gear unless you let of fuel. I've taken to transmission shop and had scanned. Showed no issues with transmission but excessive back pressure.

They said it probably had a plugged up cat. So I removed cats and I still have issues.

I've changed plugs and wires in case of fouling. No luck.

Any help out there. Please. And thanks in advance.

 

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[muddkatt]

The catalytic converters, spark plugs and wires, or fuel pump don't have anything to do with the transmission not shifting into the next gear, UNLESS it is running so bad that the engine will not reach the red line (5500 RPM's give or take a few hundred because I don't remember the exact number off the top of my head).

[chzball]

The catalytic converters, spark plugs and wires, or fuel pump don't have anything to do with the transmission not shifting into the next gear, UNLESS it is running so bad that the engine will not reach the red line (5500 RPM's give or take a few hundred because I don't remember the exact number off the top of my head).

Right. But the only codes showing up are for the o2 sensors. It will hit around 5000 remember not sure on exactly how hi but it feels like it's got tons of power..

I'm stumped.

 

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[Jake Bayman]

Hello, I know this is out of nowhere but, I really need help. My 99 GMC sierra 1500 has high RPMs, the cruise, high beam, and 4x4 light all turn on the moment I put the key in the ignition. None are actually engaged. Please help. I've already replaced the mass air flow sensor,