While cruising up to speed, around 40-50 mph my transmission will kind of buck almost like a slip, it got really bad in the rain the other day but if it is dry for awhile it wont do it. While it was raining it was doing it so i gave it some gas to shift and it kinda hesitated and sounded like it backfired or kinda popped. Is this transmission related or fuel related?

 

Did you ever find a fix?

 

not yet, it hasnt done it in a while but id try cleaning MAF but i think its my cats

 

Would bad cats throw a code? The more I think about it, this may be the case, but I have no CELs. I've done plugs, wires, new IAC, cleaned TB, MAF, and intake tube, switched back to a paper air filter, did fuel filter, trans. fluid and filter, and new synthetic in rearend. I started thinking it's the trans. after doing all these things, so I picked up a bottle of Lucas Oil stop slip to try as soon as I figure out how to syphon some fluid out. I'm at 92000 miles also.

 

Double check that the CEL hasn't burned out. It should come on when you key to "ON" without starting the engine. It's probably good, but could send you on a wild goose chase if it was bad.

 

do you have a non OEM air filter? if not, is the air filter lid properly seated and locked down with the clips?

 

check your trany fluid if its low it will cause that
and if it is auto it could be a sticky valve

 

Had an Air hog, but you(justin) mentioned going back to the OEM filter in another of my posts, so I did. I don't know too much about transmissions, but what do I do if it is a sticky valve? I'll check the light tomorrow daniel, never really thought about that happening.

 

there are really no valves to stick in a 5r55 since it is mostly solenoids...that wouldnt cause bucking...it would cause more of a slipping or harsh shifting...there is a PCM update for buck/jerk as well

 

I also a slipping feeling if I'm hard on the gas. The buck is usually when the RPMs are real low. If I take my foot off the gas, then hit it again and let it downshift it's fine, but when it wants to shift, I would say mostly OD, it will jerk.
It shifts real good yet, doesn't feel harsh at all. Engine runs like a top, just feels like something is up in the trans. What do you think about the catalytic converter? My GF had a Monte Carlo where her cat went, and it does feel real similar.
Also, what does the PCM update run for an 02 4.0L? I really appreciate the help man.

 

I was once quoted $135 for a PCM update at a Ford dealership. Pretty steep for a 10 minute job.

 

could it possibly be related to the torque converter locking and un-locking? resulting in the bump/jerk your feeling?

 

PCM update is .5hr so usually $45...sometimes an hour so $90

 

God I hope not, that also crossed my mind.