i noticed the engine runs at a higher rpm and the tranny shifts different but i really havent studied it. just curious, would it help you any when running someone?

 

It stops TC lockup and kicks it out of OD and also boosts line pressure a bit for faster and firmer shifts. The theory behind it is if your pulling a 30' gooseneck and going up hill you dont want a pansy smooth downshift because that can cause problems in the tranny, plus you dont want to haul ANYTHING in OD. If you do, kiss your tranny goodbye. Tow haul is also good for if you want to go fast, i always put in in 3rd manually and put tow haul on when i race.

 

It also allows the motor to rev higher in each gear before shifting. I believe the shift point is raised to 2k under normal driving conditions when in Tow/Haul mode.

 

I dont know if this is the case with the 4L60 but I know in the 4L80 with Tow/Haul on it will shift into O/D. Basically from what I know having Tow/Haul on will hold gears longer, shift harder/faster and downshift with less pedal action from the driver. It will also allow for more engine braking while going down a grade so the driver doesnt have to rely so much on the brakes. I have used this on a 2500 HD with 2000+ lbs of pipe (20 ft lengths) on an overhead rack and I can attest to how it works. Very ingenious system!

 

Ill put it to the test at the track tomorow night (Wed).
in D with tow/haul, and in 3 with tow/haul
and to compare the same without tow/haul
ill let you know tomorow night.

 

thats awesome man. if i had a track closer by then id try it. appreciate the help

 

its my first time ever at the drags and the truck is stock, sooo.... no big suprises.

 

The first time I took my 2000 to the track I tested with and without T/H mode and didn't gain anything. I think it was actualy a little slower. But I was just playing around that day and hotlapping the truck. I think about 6 passes were all within a tenth of each other.

 

the 4l60e will shift into overdrive in tow/haul mode but you have to be going faster than 65mph and not be putting a load on it (ie. going up hill) it will kick out of overdrive at the slightest hint of load. I tow a boat with mine quite regularly. It will also drop out of overdrive if your speed drops below 65 mph. I tow my 3500# rig in overdrive at 90mph quite often with no problems. the tranny temp never gets over 200 Oh and I have been doing it that way for 4 years.

 

my truck went .8 slower in the 1/4 mile with tow on. it shifts at a lower rpm not a higher one.