Spartan 300 EL w/ tow haul mode???

[F250Marine]

Tonight I picked up cheap commuter car, to save on fuel. I towed it home using a car dolly. I have been told to always tow with the truck in tow/haul. I am running the spartan 300 EL tune. As I was cruising home with the new ride in tow and the truck in tow/haul (no cruise control) the truck started to shutter pretty bad. I checked my gauges and everything seemed to be good. The t/c was locked and I was only doing about 55 mph. Anyone had this happen or know what's going on? Should I use tow haul when running a tune? Should I have dropped down to the 210 tow tune?

Side note: I was towing a little Nissan Sentra. Not much weight at all, and it was only for about 25 miles. This is the first time I have towed since being tuned.

[Truckmaniac]

I tow a 7,500# fifth wheel travel trailer with my Spartan 250HP-EL tune. I don't use the tow/haul mode and it runs fine. In fact, it performs better than the 210HP-Tow Performance, as far as power, fuel economy and EGTs.

I don't know how switching to tow/haul affects the transmission "learn" process, so your transmission may have been "confused".

[F250Marine]

Yeah as soon as I took it out of tow/ haul it was fine.