After receiving so much help on my IBC issues I thought Id try one more issue.

2005 f350 6.0 4x4

having an issue with my Tow/Haul. it works fine up to 55mph, hit the tow/haul to turn it on and rpms jump around 300 or so, hit it again and it turns off and RPM's drop back down. But as soon as I get above 55mph and hit the tow/haul nothing happens, tow/haul indicator comes on but no jump in RPM's.. The RPM's are already higher than they used to be, at 65mph the rpms use to be around 1200/1400, then would jump up when the tow/haul was turn on. now at 65mph the RPM's are at all ready at 1800.

Ford says nothing is wrong, I went for a drive with the Tech, he had a computer hooked up to the truck and watched the transmission, I showed him what I was talking about and he siad "I see what you mean, but the tranny is doing exactly what it is told".

Any thoughts

 

That sounds like normal behavior.

Tow/Haul mode changes the shift map. What you are seeing at 55 MPH with T/H activated sounds like the converter unlocking, or possible a downshift. Either way, the computer is telling the transmission to do this because that is what the T/H map says should happen at that RPM/Load/Throttle position. At 65 MPH, the map for T/H and normal mode agree on the gear you should be in, so nothing happens as you shift in and out of T/H mode.

One tow on my truck, towing about 9000 pounds into a stiff headwind, my truck would not shift into high gear at 55 MPH in T/H mode. Increasing my speed to 60 allowed the transmission to shift into high and allowed the RPMs to drop.

 

Above about 55 MPH there is no difference in operation with tow/haul on or off. There doesn't need to be a change in RPM with tow/haul on at that speed. All that could do is burn more fuel.

 

12 months ago when I would be driving at 65mph, I would be pulling some where around 1250-1350 RPMs with the T/H off, now under those same condtions Im pulling 1800. something has changed.

I good friend I work with has the same truck, both f350 6.0's 2005 crew cabs, Same exact truck just a different color. His truck does not act this way.

at 65mph with T/H off his RPMs are down under 1400. So something has changed

 

IIRC, I've only noticed at about 1600 rpms
( since that is the advertised torque curve)
that mine runs about 1600 rpms or so without tow/haul....

oops sorry - the jury will ignore that outburst wrong year truck !

 

Is this comparing your new trailer to the old? Your new trailer is heavier, the truck has to work harder to pull it, can you speed up or slow down to see if it will shift? Or is this unloaded?

Are the gears the same in your friend's truck?

 

No, this has nothing to do with the trailer, all speeds and rpm's given are when I'm NOT pulling a trailer

 

How big are your tires? Because I doubt that any truck would be doing 1250-1350 at 65 mph. You might be misremembering that.

 

tires are 275 70 r18, yes I could be wrong, but I know it wasnt over 1500, because when I would turn the tow haul on I would watch the RPM's jump to 1800/1900