150,000 miles. So it's definitely not average for it to have to hit passing gear to maintain speed on hills on the highway

 

Plenum, plugs, wires, cap, rotor, timing chain and gears. You will be happy again.

 

Time to empty your wallet.

 

Okay so I changed the plenum pan and gasket used the Hughes kit and fel pro gaskets. And the motor runs alot better no more pinging when you get in it but it still loses power up hills. After getting on the highway when you hit a big incline at 70 the speed will drop to 60. After driving for 5 or so miles it stops and will perform much better. My question is what could cause that. The guy I bought it from said he had the transmission rebuilt less that 20000 miles ago. I checked the fluid in park and it was good I checked it in neutral and it was a little low is the reading in park more accurate than the neutral reading. Could the filter and fluid be the problem or the bands need adjusting. All past and future help is appreciated

 

Oops, only in neutral. Park will give you a false reading. Top it off in neutral and see how it goes. But it doesn't sound like that's the problem...

 

If it's a steep incline sounds normal to me. Do you have a lift, big tires at all? What gears? What RPM do you rev at 70mph? Remember you are trying to push a heavy truck with a small underpowered V8

 

It's at 2000 rpms at 70. Not sure what gear just all factory wheels tires and suspension what makes me think something is wrong is after it heats up it doesn't do that doesn't lose speed up hills.

 

ive had that issue mine was a clogged cat with bad 02s

 

mine does this too, but ive got 35 inch tires and a lift. would putting 4.10 gears in help me with this?

 

Yes, yes they would. 4.56 would help even more.