Ok Im new to the 7.3L world and have always had d-maxes.. I outright love this truck and glad I made the decision to get it instead of another 60k new one.

I pull a single 25' car hauler ,weighs roughly 2000lbs empty and never tow anything that weighs more than 5000lbs. I hate how this truck pulls in 2nd and 3rd.. Yesterday I pulled over on the side of the interstate to water the tires down I was on a pretty good incline and as I pull out into traffic in 1st the truck pulls great! shifts to second and the rpms sit at 2300 and the truck pulls slowly, shifts to third and still sits at 23-2500 and pulls as slow, then finally after 1/2 mile the truck shifts to 4th and locks then it pulls good again.. It feel like its slipping in 2 and 3, the truck does not slow down, and I can give it more fuel and I can feel a tiny bit more of a pull, its just that its sits at that rpm and the trucks speed takes forever to catch up.

Is this normal? I also have a buddy in TN that says his does the same thing with his 38' car hauler.

Maybe the convertor is not locking up in 2nd and 3rd? The 4th gear shift is weird too but livable.. it shifts to 4th and the convertor locks up all pretty much at the same time.

I dont drive to aggressively either, the pedal never really goes to about 50 percent.. It just feels like Im tugging 20000lbs in 2-3. trans is stock, truck has 307xxx now and there is a magnafine filter installed, so Im taking a guess its not the first trans.. And without the trailer it pulls great in 2-3.

Is this normal?

 

The TC usually will lock at about 45 MPH. If you have tow tunes you will notice that the transmission will shift a little slower than regular tunes. When driving in the snow and ice I will use my tow tune to ease into the throttle a little better.

Much of what your feeling is the tunes and also the TC slipping as it should be (within reason) until the PCM sends the signal to lock it.

You can wire in a simple mod to lock the TC on demand with a switch, You just need to be careful you unlock it when slowing down.

Guzzles TC Lock Mod: Welcome to guzzle's TC Lockup Mod Web Page

 

mine dose the same thing, the TC is working fine.

 

What tunes are on the TS chip? Tuning has come a long way since that truck was new.

And heck, mash the pedal next time and see if it pulls better.

 

If the transmission is slipping it will be obvious. The fluid will be burnt black.

The converter will only lock in 2nd at more than 75% pedal. Third is similar. It does lock during the 3-4 shift at most pedal positions.

 

I am using the TS chip for now, I had both the duramax that i was getting back to stock and putting this one together so I was cash limited and a local friend has one and seems to work OK for him.

If I add the switch, will the truck up shift normally if it is on? or do I have to make it like a splitter on a big truck and activate it in each gear each time? Im just thinking that its cold out now so this might not be doing to much harm but when its 80-100 outside this thing would have to get way to hot and create damage..

Thanks Mark for the 75% comment, I dont think Im near that for TP location, maybe ill hook up the mentor today and see where things are at. As far as mashing the pedal I would love to but when things dont feel right mashing the go pedal usually hurts things more.. I know that im not blowing through the converter as I can feel (slightly) and see it shift..

I really dont think its locking up in third though most of the time, as it will go from 2500 not moving very fast at all to 4th and lockup all within 2-3 seconds then it pulls much better.. Most of the time... the other day I locked out OD for a few minutes and came to a big hill and it pulled great once like it was a new truck, maybe it was locked then?

on these trucks what is the od button doing? switching from 4th to 3rd? or locking out the converter in 4th?

 

OD is exactly that an overdrive gear. You can call it 4th gear if you like or overdrive. Technically it is a 3 speed with overdrive, still 4 forward gears.

Using the OD cancel is basically just keeping it from going into OD where you get lower than a 1:1 ratio. Pulling on hills or where the transmission is hunting for the right gear is when I cancel it. Just makes it easier on the transmission if you tell it where to be IMO.

 

Technically this is a four speed transmission where fourth gear is overdrive. The the OD light is on the transmission won't shift to fourth gear. It does not lock out the torque converter lock.