OK guys, I need some help here. Lately while driving if I hit the gas less than half throttle from a stop light, around 2K-2500 RPMs or so, my truck will buck and hesitate a bit before shifting to second. I can literally watch my tachometer jump instead of rising smoothly. However, if I hit the gas more than half throttle, it runs just fine. I can take a video of this if it's unclear too.

What can cause this?

For reference here is what I have replaced lately:

Transmission
fuel pump/filter
plugs/wires/cap/rotor

 

Anyone?

 

Assuming there are no codes, I'd next look at the live data stream as well as transmission line pressure.

Line pressure should vary depending on throttle position & MAP values so you may have a sticking valve that works fine under higher line pressure (higher throttle angles - lower MAP values), but sticks and doesn't smoothly engage 2nd under lower line pressure (lower throttle angles - higher MAP values).

Does the RPM shoot up or down? A video would likely help.

 

RPMs don't shoot, per se. They jump, I guess is the best word. They'll stick at 2200 for a second, then jump to 2500, then 2700 etc, then it'll shift and be fine.

The trans was just rebuilt less than 3000 miles ago, is it possible it could be sticking already?

I'll take a video on my lunch break and put it up here.

 

Doesn't look as bad as it feels in the videos, but hopefully this helps:

1-2 shift chugging video 1 with commentary - YouTube

1-2 shift chugging video 2 - YouTube

1-2 shift chugging video 3 with commentary - YouTube

Hopefully those help a bit.

 

It really looks like a transmission problem. Since it was rebuilt so recently, I'd take it to them and have them diagnose it.

 

If this trans is going bad too, I'm seriously going to cause some crap...

Anything else you think it could be that I can check out on my own? I don't really have the cash or time to take the truck all the way back up there yet again.

 

When they rebuilt it, did they replace the servo pins & pistons? A leaking 1-2 servo could cause this problem.

It really looks like a lack of apply pressure to the clutch during the 1-2 shift causing chatter in the shift. It can lead to premature wear/failure if left unrepaired.

 

Yes, new upgraded servo, clutches, etc, after I blew up their stock rebuild in 2 weeks.

I should also mention that I had this problem before and my spark plug on the drivers side front of the motor was really loose. I tightened it up and the problem went away for a couple days. Could just be a coincidence, but it could be relevant.

 

I don't see how the two could be related.

What servo did they install? Did they install a new pin? Which pin did they install? If it was the aftermarket longer pin, was it adjusted to maintain proper travel?

To check any of this, you'll have to open up the transmission in one way or another which could be further reason for them to leech money out of your pocket.

From your previous dealings with this place, they sound like a bunch of 4L60E illiterates. As I said in your other thread, a stock rebuild should not have blown up with what you were doing to it. They screwed it up and then made you pay for it. Worse yet, you did pay for it and now have further problems...

IMO, I would find another, more reputable 4L60E shop and have them diagnose the problem then take the findings to the DA for your area and discuss a law suit.