99' tahoe shifting issue

[PotentialTahoe]

I have 99 tahoe 2door w/ 128k miles 4WD. Normally when I shift from park to drive, i feel the power at the brakes immediately as in I can let off the brakes and just the idle power itself will move the vehicle ahead fairly well with no use of the accelerator. NOW when I first start the truck up and wait a few minutes, I shift from park to drive and I feel a large joult, almost if the rpms were too high when the tranny went into the right gear, when I brake I can still feel the normal power under the brake pressure, but after a few minutes of driving, I now can come to a stop and then release the brakes while in drive and the truck barely moves and I have to really gas it for it to move almost as if the transmission was slipping, it doesn't rev up really high though, and I checked the tranny fluid, it is good and red, fresh. I am confused on what it is, I want to maybe say torque converter? or transmission is going. Just to let you also know I just got done towing a fairly light boat 4000lbs about 200miles, but had no problems or issues with the tow, transmission was fine then.

 

[Colabella7077]

Yeah I think maybe pulleys or cats. Pulleys because when I did pulleys the gas would jump. If you start your hoe and the RPM is higher than normal, it could be a lower intake gasket. MY ISSUE- I'll have the pedal all the way to the floor and it will come to 5000rpm with the truck not really moving as much as the amount of gas im giving it and it will wait about 3 seconds until it shifts down...Also, my exhaust system will make a popping or flanging sound.

 

[Colabella7077]

My bad, the cats could be clogged and causing your shifting to be irregular...I got that issue as well.

 

[PotentialTahoe]

When you say "cats" are you referring to the catlytic converter?, I'm not sure that I understand how those would effect the clunking of the transmission? I also hear a flanging sound coming from my exaust.