As some of you know, I rebuild my transmission the 1st of July, everything seemed ok since then, but have noticed the transmission lagging a little between shifts, and when you get over 45 mph there is a vibration/surging problem. If you let off the gas completly, or if you put your foot to the floor it goes away, but you keep the truck around the same speed, the vibration/surging is there. What does this sound like to your guys?

 

Many different things.

TPS Issue,
Torque Converter Issue
TV Cable adjustment wrong
Miss Fire
O2 sensor malfunction

Are you tossing any CELs?

 

I got a CEL about 2 days ago saying the O2 sensor's or the cat are bad, but the problems started weeks before that CEL. The TPS has already been changed. No miss fire, but when I rebuilt the transmission the torque convertor didnt get changed, and the TV cable did get adjusted.

 

Sounds like the pcm trying to adjust the fuel curves to lean or richen the mixture due to the cat/o2 codes its tossing, and yes it can act up for weeks before it tosses a code. I think its 5 cycles or something.

How is your gas mileage?

 

The fuel mileage hasent changed from before or after the CEL. It is still getting horrible fuel mileage!

 

Whats your MPG?

Most of the time emission codes will pop CELs pretty quick, but sometimes they don't if its minor. If your ~10+/- 1. Then somthing is wrong. Te cheapest thing to change would be the o2 sensor (pre cat) to see if that fixes the problem. Everytime i had the surge you are talking about its a faulty o2 reading making the pcm go haywire.

 

The best fuel mileage I have seen from the truck is 15 mpg. I know I should be seeing better results than that. The 15 mpg was from a 380 mile trip doing 65 mph, no stop and go, all highway. Since that trip I have averaged about the same, if not worse (14.8-14 mpg)

 

15 ins a 4x4 QC is pretty damn good. I get about 9.5mpg city, 11 highway, before i was moded it was around 11.5 city, 13-14 highway.

 

When I bought the truck I was seeing 17-19 depending on wind and speed on the highway, and that is with me, my wife, my 3 kids, and the bed full of luggage. Granted, the truck has 180,000 miles on it and I know the truck will go down hill slightly with mileage. Considering I have put a TON of work into this truck since I bought it, I figured the truck would get better, not worse!

 

What codes are the truck tossing, list them, and im guessing you have the 4.7? or do you have the 5.2?