OD Off

[flyrod40]

We have a '97 Ram 2500 Cummins SLT auto with the 3.54 rear. My wife pulls her 27.5 foot aluminum goose neck horse trailer with one horse and some tack which in total weighs about 8,000 pounds, I think. The truck runs great, we are the original owners and it only has 105k miles on it. We have always had it serviced by our local Dodge dealer per the service schedule "B". She complains it does not have enough power when towing. We have never used the OD Off feature. After researching on this forum and reading the page in the manual about OD, I get the feeling we should be using OD Off. Could some of the members please respond and give me some guidance regarding this feature. Her towing usually starts off around town and then goes to highway to and from horse shows.
Thanks in advance

I just realized that I think I posted this topic in the wrong place. I would ask a moderator to move it to the appropriate area.

 

[Ozymandias]

With a 3.54 rear end you sure should use that feature.
In this configuration the 4th gear aka OD is a real overdrive for high speed on the freeway but everywhere else it is obsolet.
If we talk about speed, I think you can consider using OD at above 55-60mph on flat land.
3rd Gear is direct drive, means no gears are involved within the transmission. This gear is the one that can handle the torque the best.

Friend of mine uses his for 14k Trailers and he said that he has a three speed transmission as he never uses OD at all.

 

[DRAG DIESEL]

This gear is the one that can handle the torque the best.

This statement could mislead a novice. In fact 3rd gear mechanically has the least amount of clutch material as it is acting alone, where as 1st, 2nd, and Reverse have additional applied. When you are in lockup (the most important place to be) you also bring in a line pressure boosting circuit (at an appropriate throttle position) that significantly raises the line pressure to help 3rd and 4th hold greater torque input.

 

[flyrod40]

Thanks to everyone who has helped with answers. As a follow-up question what does being in lockup mean and how do I get there and keep the truck there? Thanks in advance.

 

[BigPapa]

"Lockup" is referring to the TC Clutch. It locks up solid like a manual transmission for best efficiency when conditions are right. If OD is switched off, it will lock up in 3rd. With OD on, it will lock up in OD. When you give it a bit of throttle, it will unlock until engine speed is steady again.

Some folks, myself included, put a switch in so you can manually lock and unlock it. With the switch and a modified valve body, it can be locked in 2nd, 3rd, and OD, and CAN shift up locked. It will not downshift locked and as long as it's locked, the transmission can't shift down. Most use it for use with an exhaust brake for it to work the best and not heat up the transmission fluid.

 

[flyrod40]

"Lockup" is referring to the TC Clutch. It locks up solid like a manual transmission for best efficiency when conditions are right. If OD is switched off, it will lock up in 3rd. With OD on, it will lock up in OD. When you give it a bit of throttle, it will unlock until engine speed is steady again.

Some folks, myself included, put a switch in so you can manually lock and unlock it. With the switch and a modified valve body, it can be locked in 2nd, 3rd, and OD, and CAN shift up locked. It will not downshift locked and as long as it's locked, the transmission can't shift down. Most use it for use with an exhaust brake for it to work the best and not heat up the transmission fluid.

Thank you. I think I get it.

 

[DRAG DIESEL]

Thank you. I think I get it.

The lockup switch override game is one many of us play. It can provide good performance, but can be a handful to drive to a novice. I recommend looking at a product like the ATS Commander/Co Pilot. This will automate the lockup strategies of the truck and make it MUCH more driveable.

One of my trucks in bone stock and I tow pretty heavy with it. The moral of the whole story, it try to keep the tach right about 2,000rpm and you'll have plenty of power, even with the 3.54 gear set. If you're climbing a steep hill, you'll need to let it climb above that point, but don't push the peddle so hard it falls out of lockup.

Safe travels to you and yours. Feel free to ask any questions, that's what this place has been and will continue to be all about!