Pulling long grades [u] Were are you Smokey[/u] - Diesel Forum

Bob Quinn · 10-18-2007, 01:43 PM

Morning All, I was wondering about just how the transmission is supposed to shift while pulling long grades, 5-6% 21O00 GCW. Starting at the bottom w/ OD locked out, with a little run doing about 60mph, keeping the pyro under, or at 1200 deg., watching the tranny guage. Just about to crest, speed has dropping down to about 40 or so mph, then it shifts down hard! Does that sound about right? Just wondering, new to pulling hills. I'm from the flatland.
Thanks everyone!!
BOB [img]/forums/images/%%GRAEMLIN_URL%%/confused.gif[/img]

SmokeyWren · 10-18-2007, 07:06 PM

I'm here, but I don't have any experience grossing over about 17.5k. My hot-rodded PSD has never downshifted from direct drive to 2nd gear, but I can imagine it would be a jerk shift when it did downshift if you were showing 1,200 EGT with pedal almost to the metal.

You don't mention any sort of chip or programmer in your sig, so maybe you are towing without a towing tune? If you have a 4.10 rear end, stock-size tires, and about a 60 HP towing tune, it shouldn't downshift out of direct drive at only 21,000 pounds gross on a 6 percent grade.

Bob Quinn · 10-18-2007, 08:34 PM

Thanks for the reply Smokey. I'am running stock with 410's, not chipped. I'v had that happen a couple of times now. Am I in it to hard? It pulls a long grade better from a dead start at the base of a hill then it does with a head of steam, but when it has to down shift it seems to shift allfull hard.
Thank you [img]/forums/images/%%GRAEMLIN_URL%%/wink.gif[/img]
Bob Q

fulltimer50 · 10-19-2007, 12:59 PM

You need to learn when it will down shift to 2nd. I find that point below 45 so I will let off and maually down shift. Dont need to very often. Then I can feather the fuel so I dont get any jerks, hard shifts or high revs. Like Smokey says a chip/program will help a lot.

Bob Quinn · 10-19-2007, 07:51 PM

Thanks George, what is a safe RPM range to downshift manually?
Bob Q

fulltimer50 · 10-19-2007, 10:58 PM

I work with speed and grade not RPM. Or boost and EGT. Just have to experiment. Put it in 2nd and see what RPMs you get at what speeds. You can do this easy enough. [img]/forums/images/%%GRAEMLIN_URL%%/smile.gif[/img]

Bob Quinn · 10-20-2007, 12:31 PM

THanks again George!
Bob Q

LeRoy · 11-02-2007, 01:47 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fulltimer50</div><div class="ubbcode-body">You need to learn when it will down shift to 2nd. I find that point below 45 so I will let off and maually down shift. Dont need to very often. Then I can feather the fuel so I dont get any jerks, hard shifts or high revs. Like Smokey says a chip/program will help a lot. </div></div>

The only long pull experience I have is I-70 and I was stock at the time. I did what you did going up to Vail Pass. The only time I had to do that, but Im only towing aprox 8500.

LeRoy