Hello, I just bought a 1998 dodge ram 1500 series truck 4x4 with a5.2 liter engine and auto transmissionfrom a friend and I'm having some problems, maybe someone can help me because I'm at a lost. I thought I got the truck for a deal only paid $1500 for it. The truck had bad rearend bearings, theywere making nosie no big deal. So I changed the rear endfrom another truck and I made sure the gear ratiois the same 3.55 The problem is from 0 to 20 mph I have no power can't spin the tires even if its wet out.After 20 mph the truck gets up and goes no problems. The truck had the same problem before I changed the rear so I don't think its that. The other werid thing I only get 80 miles to a tank full of fuel. Itried changing some parts sohere is the list of things that have been changed:Tune-up, plugs, wires, cap, rotor, fuel filter, air filter,new tps sensor, new map sensor, new cat from dealer not aftermarket, new fuel pump and has 50 psi of fuel, new rebuilt transmission and torque converter, tried changing computers from my other truck that has no problem spinning wheels no help still the same I was worried about that death flash because my computer said reprogram on it,also tried racing computer jet stage 2 chip no help,also spacer for throttle no help, The only thing left that I haven't changed is the plemun gasket. Could it be that? Can someone help me out before I set this truck on fire and junk it?

 

damn i was gonna say cat but youve already changed it. is there a lift on it? changin out the gears to 4.10 would help alot id say

 

Wow 80 miles to a full tank! That's pathetic
I was thinking plugged cat too. Is it possible the old cat came apart and plugged the muffler? I've seen it a few times.
Definitely no fuel leaks?
Does it idle smooth?
try dropping it into low and accelerating (trying to rule out a trans problem)

Could be a bad plenum. Does it ping?
Unplug the PCV from the valve cover and plug the hole in the valve cover with you finger.
Check the PCV breather in the other valve cover for vacuum. Cover it with your thumb. Pressure build up is good after 5-10 seconds at idle. Any vacuum is bad = bad plenum gasket