Bought a 01 duramax, 1 month ago. The truck did wonderful, even on a ski trip in the mountains. But yesterday I hooked on to a pontoon boat ( approx. 4000 lbs ), This is when things went bad. I had never hauled a trailer with this truck prior. We hooked up to the boat and trailer and headed down the road. I started the transmission in drive and had the tow/haul on. Got up to highway speed for around 4 miles and the truck just shut down and service engine soon light came on, it was still running but would not go over 25 mph and rpm wouldn't go over 2000. Limped back to the lake and put a new fuel filter on, truck sat without running for 30 minutes. Truck started fine and test drive was performed w/o boat. Truck ran great and the only thing that slowed it down was the wall at 97 mph. Hooked back up to boat and the same thing happened at about the same spot on the highway. Even when truck was in park it would not go over 2000 rpm. Dropped boat off, let truck sit, truck ran fine all 250 miles home w/o boat, which was purpose of trip. Truck is at chevy house. Any ideas.
dustin layman

Not really an allison expert (& not sure that this would make a diff), but I don't think you need the tow/haul enlisted for 4000lbs.

I get all kinds of quirky behaviour from my truck when hauling relatively light loads with tow/haul on.

maybe NSBU switch on the tranny. can make the tranny do some strange things. tow/haul should not do anything quirky unloaded or towing, a good feature any time you tow and will help with slowing (save on the brake wear). NSBU switch is about $60, you can do the labor it is not that difficult if that is the problem.

Trans is fine. Look at the engine. I would bet a p093 code is stored. Have it scanned even if the SES light isnt on.

Tow/Haul with any load or even heavy weight in the bed is helpfull, but not nec.

My 01 woulld defuel when it was stock and I towed up a hill. I believe it was a overboost. Get a Juice and it will fix it. Dealers coul not fix it. Juice did.

That's if it was overboost. If not, do you know the history of the truck? Was it thrashed> Did it have gauges? Reason i ask is the tranny could be slipping from being slipped too many times. When she slips you get that limp.

trans limp will mot limit rpms

Did you get any service records with the truck? I wonder when the last time the fuel filter was changed

Limped back to the lake and put a new fuel filter on, truck sat without

Read MAC

Limped back to the lake and put a new fuel filter on, truck sat without

Read MAC




:o

Think the key here is that truck only acts up with boat trailer hooked up. Could there be some kind of feedback or ground problem here that causes this? With trailer wiring being in main junction box along with the other circuits, there is a strong possibility that somewhere in the past a few circuits got screwed up or maybe some wires chafing? Also look at left frame rails as all rear wiring is routed along rails. Hope this helps a bit

could be fuel leak.