trans kickdown and vapor lock?

[etchasketch]

Have an 05 3500 with K&N filter and 4" exhaust and predator. Recently when i have the tow mode in and pulling about 8000lbs, vehicle has downshifted from what is it, 5 to 4 and then when passed the traffic it won't shift back and i'm redlining it..till i get it pulled over..and let it cool off. pull program out and everything is fine the rest of the trip.
second recently i was pulling same weight in rain.. vehicle acted like it ran out of gas, feathered it to a parking lot. let it cool off for a few then tried again..nothing. replaced fuel filter, nothing removed program, started right up.
third, recently was on highway with a friend who was impressed with the power a diesel had. i floored it and went nuts. let off the gas and then the truck would not go over 70. took program out and bingo runs fine.
whats going on? i have part# U7185 serial# 148631

[Skoryaro]

What HP tune are you running? Sounds like you may be putting the tranny into limp mode - are you giving the tranny time to re-learn after programming before you are aggressive with it?

[mikel]

Yeah, definitely sounds like the trans is going into limp mode.
This will often happen as a result of the tranny slipping a bit.
The extra torque from the tune may be more than the tranny likes when in OD on the highway.

Thanks

[etchasketch]

for the first two i was in the tow mode or 40hp..pulling approximately 9500lbs and carring about 700lbs in the bed..the third was empty and nothing being pulled besides a cooler of beer.
just went out and noticed alot of egr code faults..is that something..?

[etchasketch]

and i had it in trailer mode on the shifter too..

[mikel]

You should have the EGR checked at the dealer.

Thanks