480LE shift pattern

[drl]

I have 98 6.5 diesel in Crewcab 4X4 3500 dually. Just completed 10000 roadtrip with 2500 lb camper on back. Alaska to Arizona, back to Washington. Bought truck and added camper just before we headed south. 125000 miles. Cleaned up intake and added 3in to 4 in exhaust. My question is this, I can feel the torque converter lock in 2nd and 3rd gears. When hill climbing I am running between 2200 and 2700rpm and torque converter will release as hill steepens and load increases. I do not however feel torque converter release in OD, it goes right to 3rd gear on hill. Which is OK except I got to catch cruise control to keep EGT down. When I nudge shifter from 3rd to OD it seems Torque Converter lock is real quick as to be not noticeable. When working into a strong wind I am running 3rd, 2600 rpm, and 55 mph, with EGT at 1150 F. Was wondering if I might have another gear I am not getting, ie. OD without torque converter lock, might help keep EGT down. Been working this way since I bought truck. Been absolutely reliable and comfortable, except for replacement of primary fuel pump. Fuel burn is 11.5 mpg hwy, 10+mpg high wind, hills.

[DmaxMaverick]

Torque converter unlock isn't, necessarily, an "extra gear". Under load, the TC will bleed power and generate heat. More load means more power loss and greater heat, which ultimately gets dumped into the cooling stack. Ideally, the TC should lock early, and remain locked as much/often as possible. In most cases under load, an unlocked higher gear will be near the same engine RPM as a lower/locked gear. The lower locked gear will offer more power and much less heat generation. This also results in improved overall economy. If your TC is locking properly, don't sweat it not unlocking when you think it should. There's no gain forcing or anticipating an unlock. If EGT's start heading north, either slow down, or drop a gear. Or, upgrade to a CAC system.

[More Power]

To help make this a more engine-related thread, I'll offer the following suggestion.

Think of the turbocharger as a torque adder - more boost pressure = more torque. The 6.5TD tends to produce the most boost pressure in the 1800-2200 rpm range. That's where it pulls best. Higher engine speeds cause boost pressure to decline. Less boost tends to produce higher EGT and engine coolant temperatures, as well as less engine torque.

So, try running the truck in ways to keep boost pressure highest while towing. Jim

[arveetek]

In other words, what you experienced is normal. When towing, my rig will downshift from locked OD to unlocked 3rd, and then lockup again. In fact, if there's too much throttle input, it will stay in unlocked 3rd. I'll usually ease off the throttle in order for it to lock up and stay locked.

Unlocked TC = excessive heat generation.

Casey

[drl]

Thanks for the reply. My engine/trans behaves the same way. Before I start up a grade I pull down to 3rd. After a brief unlock, I feel the TC lock-up, up we go. Under a hard pull it will eventually unlock, then down around 2000rpm I pull down to second. 35 to 40 mph. Just wondering if that was normal as have had not experience with this transmission with load. I get best pull power around 2600rpm.