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When your pulling up a slight grade on on the throttle with the trailer in tow I can see the TQ unlocking but when your at low throttle situations the TQ should lockup. There is a noticable difference in rpm vs a locked and unlocked TQ. I don't tow the weights you do but the variation in rpm seems odd to me.
Are you running a non stock tune?
The Scangauge II has an Xgauge code to monitor the Converter Speed Ratio (in to out) Never tried using it but it may be able to show when the converter is locked and unlocked.
I may have been running the Superchips tuner set with the towing mode, but I really don't remember. I'm going to check those rpm values againthis weekend when I tow the trailer. I'll check the DTC's today with the tuner.
It should work for you. I am pulling a Jayco 5th whl. It scales out at 11,200lbs. I have a 2000 V-10 4x4 with the 2Valve. It does fine. Your truck will be a bit heavier than mine, mine is a Super Cab short bed. I also have the 373 rear end. You won't be first to the top of the mountain. But if you aren't in a hurry it will get you there. Just put it in second gear and keep the Rpm about 3,500 to 4,000. If I remember right that will be about 50 to 53mph.
I found on the flats I get better mileage by locking out overdrive and running about 60mph.
My Truck scaled empty with full fuel, my wife and I in it & the fiver hitch installed at 6,940. My pin weight loaded was2300lbs.
On the flats here in Illinois I get low 9's to low 10's for miles per gallon. They told me my traile was to heavy for the truck too. But I have been very happy with it. Hope this helps you. That engine is a work horse.
Forgot to add, get a transmission guage. get something that plugs into the OBD port. I have one that is inst in the test port and I have a Scan guage that plugs in there is a 40 to 45 degree diff. My temps are fine as long as I'm not in the mountains. If you are getting much over 240 it might be a good idea to pull over and let it cool. Change fluid if it gets burnt look. I normally change mine every couple years as a precaution. But that is just me, fluid id cheaper than Trans.
Also I had 700lbs to spare before being over on truck GVW, but was no where near over axle ratings.
Forgot to mention mine is a SRW, nota dually
Good Luck : Hope I helped
judgerr
+1
Also have a 2000 SRW that handles that weight no problem. It does not fly but keeps up with traffic.
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