Towing in overdrive

[herd]

No need to beat up on an engine when the peak torque is at 3200 RPM. Or 65 MPH in 4th gear unlocked. If the load doesn't require it, the Ally will drop down to 2800 locked and RUN up the hill at 65 MPH. But I do go thru the gears at the points where it goes from peak HP to peak Torque at each shift. The HP point is 4500 RPM, Torque is 3200. Factory redline on the 8.1L/496 is 5000 RPM.

Longest life on an engine comes when they are run at about 3/4 load-3/4factory redline.

You guys are so far ahead of me in understanding and utilizing this equpment as it was intended and knowing how it should react, but me, I'm still confused. I am going to hook the truck up to the camper Monday, and take it over to the Allison tech and let him test drive and decide what is wrong and needs attention.

Maybe I am being just a "nervous Nellie."

 

[Diamondpilot]

Herd, that is a smart choice. It will give him a good understanding what you put the truck through. Just make sure to fill the camper with the normal stuff you take to get the weight close.

Chris

 

[Builder]

You guys are so far ahead of me in understanding and utilizing this equpment as it was intended and knowing how it should react, but me, I'm still confused. I am going to hook the truck up to the camper Monday, and take it over to the Allison tech and let him test drive and decide what is wrong and needs attention.

Maybe I am being just a "nervous Nellie."

No you're not. You're being smart. You'll get it fixed by the guys who know what's best. You're actually further ahead than you think for understanding the right proceedure for getting it fixed.

Good luck. Let us know what happens!

 

[Renze]

The water temp gauge is good to monitor BUT... a heavy load pulling up a hill and you could damage a diesel engine before the radiator temp would rise enough to alarm you especially if you aren't exactly stock.

You get a much better indication that responds more quickly by using an exhaust gas temperature (EGT) gauge, a pyrometer installed in the exhaust.

I could seriously overheat and potentially melt the top out of a piston under certain conditions if I ignore the pyro and rely on the water temp indicator.

Pat

At lower rpm, if it cuts your fuel consumption it cuts the heat load on the engine because less fuel is burned. However due to the lower revs, more heat is produced per working stroke. At 2000 rpm, combustion takes place 18.3 times per second, however due to heat transfer resistance, there is no way that the piston temperature peaks at combustion and drops at intake stroke: The piston simply cant dissipate or take up enough heat quick enough to follow the air temperature at 18.3 cycles per second.

With a stock engine in the long haul at low rpm, the water temp is safe enough. If you need a pyrometer to be safe, you're driving on borrowed money anyways and you should have bought a bigger truck. Yes, you can burn pistons, but if it saves fuel and you keep enough rpm to spin the water pump fast enough, doing the same job at lower rpm wont hurt your engine.
Now if you'd be overloading the engine so much that you need to take the full power at full rpm, medium duty truck engines CAN burn pistons.

I would be worried more about auto trannies.

My Volvo S70 2.5 TDI, i prefer to keep it above 2000 rpm because of turbo lag on the Euro3 emission version (my previous 850 with the same engine, had better torque between 1500 and 2000 rpm) Which means i drive at least 95 km/h in 5th gear with 5000 pounds behind it. My 140hp diesel has the same 5 speed manual as the 275hp T5R racers so i'm not worried about that either.
I am thinking about chipping or installing a powerbox, to fool the computer with the turbo pressure so it injects a little extra fuel at low boost (which in turn, improves turbo spooling at low rpm so the problem cures itself)

 

[FlaDon]

You guys are so far ahead of me in understanding and utilizing this equpment as it was intended and knowing how it should react, but me, I'm still confused. I am going to hook the truck up to the camper Monday, and take it over to the Allison tech and let him test drive and decide what is wrong and needs attention.

Maybe I am being just a "nervous Nellie."

Very good plan there. If the tech puts gauges on it, it might point out any number of things. Also take it somewhere to get it weighed. Make sure you're not exceeding its tow limits. And as DP said, load it like you're going camping then. You'd be surprised how weight adds in.

 

[Builder]

They'll plug their scanner into your obd2 port and check to see what (if anything) is out of whack.

 

[herd]

Well, got the truck back from the tranny guy, and immediately went on a camping trip, about 100 miles away. Truck performed great, at least I think great, smooth shifts, no unexpected down/up shifts, most normal rpm range. Did not that in the tow/haul mode, that the shift from drive to overdrive occurred around 2700-2800 rpm's, that may be as designed, I don't know, it just seemed to hold in drive much longer. Tranny temp stayed low, around 180.

What was wrong, well the technician said nothing major, both filters were originals and very dirty, fluid was slightly burned, and the fuel filter was 3/4 clogged. Replaced the fluid with synthetic and got out around $300, parts and labor.

This week's trip was all flat land tho, so now I gotta get out on some hilly land and see how she does. Guess I'm still the "nervous Nellie."

 

[Diamondpilot]

You did good. That $300 is not bad. Figure the filters would run $50 or so for all 3 then the synthetic fluid is not cheap. You may have just saved yourself $3000 in a tranny rebuild.

Good luck with the truck.

Chris

 

[patrick_g]

Didn't read every post, but here's my 2 cents:

When you wish upon a falling star, your dreams can come true. Unless it's really a meteorite hurling to the earth which will destroy all life. Then you're pretty much hosed no matter what you wish for. Unless it's death by meteor.

Dude, that really cracked me up! I just love it!!!

Pat

 

[FlaDon]

Well, got the truck back from the tranny guy, and immediately went on a camping trip, about 100 miles away. Truck performed great, at least I think great, smooth shifts, no unexpected down/up shifts, most normal rpm range. Did not that in the tow/haul mode, that the shift from drive to overdrive occurred around 2700-2800 rpm's, that may be as designed, I don't know, it just seemed to hold in drive much longer. Tranny temp stayed low, around 180.

What was wrong, well the technician said nothing major, both filters were originals and very dirty, fluid was slightly burned, and the fuel filter was 3/4 clogged. Replaced the fluid with synthetic and got out around $300, parts and labor.

This week's trip was all flat land tho, so now I gotta get out on some hilly land and see how she does. Guess I'm still the "nervous Nellie."

Head up I-77 to the NC/VA line. Thats a good test for the trany from there to Hillsville, VA and return. Mine needed the same things done before the last trip as it had 50K on the filter and syn tranny fluid.