Overdrive

[Wayne M]

I have questions.....

When should I turn the O/D off on my '99 stock 2500 with AT?

I believe I read someone saying if driving no faster than 50 to 55 MPH run with O/D off. At about 50 MPH the engine is running 2000 to 2100 RPMs with O/D off. It also feels like the engine is really tightly wound at that speed, but it also has good pickup as well.

When running around town with the O/D off how does that effect my gas mileage?

When towing... at what tow weight should I run with O/D off?

These are probably pretty elementary questions to most of you, but I plan to hang on to this truck a long time and want to treat her right. So far with 35,000 miles on her I have not had any problems... want to keep it that way.

Thanks. wm

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1999 2500 Quad Cab, Driftwood, auto w/towing, all stock with K&N filter... add-ons = ULTRA Alum directional spoke wheels(16 x 8), over the rail tool box-LineX coated, Westin step bars-LineX coated, LineX bedliner

 

[K_Arts]

I actually use 50MPH as the magic spot.

Kev

 

[Mopar-muscle]

yes 50 is the magic number ... the cummins seems to get its best MPG at about 1700 - 2000 rpm , yes the engine sounds wound up , but that the rpm you run on the freeway ??? no real difference . i have noticed on my trip computer the mileage reading , though not accurate , jump up as much as 4 or 5 mpg when i go from a lugging rpm to the sweet spot .

as far as towing goes , as long as you aren't lugging the engine you will be ok , only real concern with od would be going up a long , steep ??? , grade . but i rarely tow , so i'm not a good guesser on this one .

 

[Guest00]

I thought that 79 was the sweet spot, kuzz the speed limit is 75. #ad

 

[BigDaddy]

Wayne,

Not taking into account MPG, I use RPM as the deciding factor for in or out of OD.
I try to keep it at least above 1,500 RPM.
Do not quote me on this, but I think I got this from the DTT forum.

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<font color=forestgreen>2000</font> DODGE <font color=forestgreen>RAM</font>, <font color=forestgreen>2500 HD</font>, 4x4 SLT, Reg. Cab, <font color=forestgreen>Forest Green</font>, Agate interior, Cummins ISB, Auto, Shift-on-the-Fly (241HD), 4. 10 LS, ABS, Trailer Tow Group, Camper Group, Michelin; DC: Fog Lights Kit, Tow Rings, Under Rail Bedliner, VentVisors, Splash Guards, Cold Weather Cover, & Mats.
<font color=forestgreen>After-market</font>: JRE 4" Exhaust, Van Aaken, High Idler, Heavy Duty Idler Pulley, Gatorback Belt, Painless Wiring, K40, Viper w/AutoStart, Clarion 6 Disk CD w/remote, UnidenCB w/Francis antenna, Draw-Tite Activator II, Alpex 255TC2C Air Horns, Continental BedRails, Delo 400, HOWES, Liquid Glass.

BigDaddy's Ram #ad
New England RamRiggers

<font color=36648B>2001 PT Cruiser Limited Edition</font>

 

[B.G. Smith]

Wayne, there are a couple of active threads on the above subject on the "Towing" forum bg

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White 99 3500, QC, 3:55, auto. most options except leather, Line-X bed liner, fiberglass running boards Rancho 9000s, bug shield and window vents, black vented 5th wheel tailgate, 110 gal. aux. fuel tank.

 

[Wayne M]

Well here's a good one.....

First as usual thanks for the advice.

Began running with O/D off around town yesterday. Got up on highway this morning and turned O/D on. Now the O/D acts like it does not want to engage as normal. When I reached 70mph it was like it was sort of engaged and sort of not. I was running about 2125 RPMs at 70mph. Normally with O/D engaged the RPMs would be around and just below 2000. Without doubt if I was running 70 with O/D completely disengaged the RPMs would be way higher.

Any suggestions? I have 33,000 miles on the truck and never had any problems with anything... . HELP!!

Thanks. wm

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1999 2500 Quad Cab, Driftwood, auto w/towing, all stock with K&N filter... add-ons = ULTRA Alum directional spoke wheels(16 x 8), over the rail tool box-LineX coated, Westin step bars-LineX coated, LineX bedliner

 

[Bill Kondolay]

Wayne,

Your TC Clutch is not locked up, which is quite normal when your transmission temperatures are low. You could have a problem with you transducer which does act up once an a while. The part # for the transducer is 56041403AA. At 70MPH you have a fair amount of air flow cooling your transmission.

Stefan Kondolay

PS: I have heard my dad (Bill) tell several people to make sure that they keep the RPM's above 1600.

 

[ARARAR]

When's the last time you had your PCM reflashed. DC is constantly making change to the software in the PCM. I had some transmission upgrades done a few months ago and every thing seemed fine until the first time I towed. The the transmission started doing strange things; come to find out that there have been 6 different software upgrades to my model year and the increased pressures from the valve body and torque converted brought them to light. Since I don't take my truck to the dealer for service, I took it back to my mechanic (KEN IMLER DIESEL REPAIR in SACRMENTO) where I had my work done and he suspected that was the problem right off hand. He checked it out, sent it into the dealer to have it reflashed(after removing my VA and boost mod)picked it up and didn't charge me a dime. How's that for service. If this sounds like a plug for this guy it is. I thought my upgrades were great before this all happened but what an eye opener after my PCM reflash.




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98. 5 2500 QC,SB W/ camper shell, whitw w/driftwood lower, 2wd,3. 54, loaded w/o leather,chrome Westin step bars, BD tc/vb and pressureloc,w/trans temp,4" BD exhaust from turbo back, firestone airbags, heavy duty pullrite hitch, Bug sheilds, 4x4 type mud flaps front and back, Amsoil bypass & air filter. Dual pyro-boost gauge,pillar mount, PS boost mod and elbow, Pacbrake w/ BD Autoloc,VA cpc and fuel pressure gauge, Bosch 275's.