lagging/holding back on a 4l80e

[chevydad]

anyone expeiance anything like this.

2005 2500hd 6.0 4l80e 285's and 4:10's

if i punch it down to go it will rev and pull through first fine. shifts at about 5300ish then starts pulling in second.at aproximately 4000rpm the tach needle seems to stop/hesitate for a second or so and the truck feeels as if it's holding back a tad before it continues on out to 5300ish. if i have my 6x10 trailer behind it with my tractor or whatever on it, it will rev to 4ish and hold there for a little then drop to 36-3700 before continueing on out to 5300ish.

sunday i had our 30ft camper behind it going up a hill. it pulled fine through first and into second. at about 3900-4000ish it held there and the truck didn't seem like it wanted to go past that point till i crested the hill then it went to 5300 and shifted.

i took it to the dealer that i bought it from 1 month ago and took the technician for a ride. when we got back he scanned it for codes and nothing. he said nothing wrong. maybe it was from the bigger tires. i said that how i bought from here. he said he could take it apart and put all new parts in and chances are it would stil do it. and it probably did it when it was new. i left. went to a friend and he hooked up the techII and checked the tire size. it was still at 245's. he changed it to 285's and i drove it home. i notice my gas mileage according to the dash is better but the tranny is no better.

anyone have this problem or have any ideas. id like to get this straightened out before the warranty is up. the warranty was only for 3 months or 3000 miles and it's been almost 5 weeks now. and about 1800 miles but i think that not right since the tire size was not change in the computer.

[NEUMANNZZ]

I wonder if that has anything to do with torque management. (especially shifting at that high of rpms with a load on it.)

[PBA]

It sounds like the torque converter is locking up. There is nothing in the transmission to make it act this way. And if it was the transmission, it would tear itself up quickly.

[popknot98]

Originally Posted by PBA

It sounds like the torque converter is locking up. There is nothing in the transmission to make it act this way. And if it was the transmission, it would tear itself up quickly.

i agree. sounds like the coverter is locking up, which it's supposed to do.

[andrewdirt101]

i used to drive 6.0s at my old job all the time. they all did that. you're fine.

[Fast305]

Originally Posted by PBA

It sounds like the torque converter is locking up. There is nothing in the transmission to make it act this way.

I am about 99.5% sure that what he is seeing and feeling is the manditory TCC lockup programmed into the PCM at 75 mph. No matter what the throttle position is the PCM will lock the converter when it reaches 75 mph.

[chevydad]

this is in 2nd gear at 50ish mph. i'm pretty sure the convertor doesn't lock up in 2nd only third and 4th. i don't really think it's the tranny anymore. i'm no efi geek but i kinda think it's related to the throttle body or drive by wire crap