Hello, guys. Looking for advice again. I'm towing a 5th wheel trailer weighing an estimated 11-12k. When I'm on the flats I keep the tranny in 6th at about 1800 RPM (approx 60 MPH). There doesn't appear to be any lugging since I'm able to accelerate OK (although I definitely know there's a load behind). Since I like to travel at about 55-60 MPH is it a good practice to stay in 6th as long as I don't perceive any lugging, or would it be preferable to remain in 5th at an RPM somewhat over 2000? I'm still new to diesels and enjoying mine very much but since I don't have an EGT gauge I don't want to harm the engine in any way by inadvertently lugging it. If you're the owner of a manual tranny truck what gear(s) are you using while towing a comparable load? Thanks for your input....Ed

2007 Dodge Ram 3500/6.7 CTD/SRW/SB/4X4/6-speed man/Big Horn Edition/16k Husky manual slider hitch

 

If you're towing with a stock truck, I wouldn't worry about EGTs. I would keep it in the highest gear that you can maintain the same speed. Sixth gear would be fine on flats. Now, where I live with winding curves and hills, my dad (exact truck as yours) keeps it in 5th. If you're around 1800 RPMs, you're not lugging the engine. As long as you keep it above 1500 RPMs, you're not really lugging it.

 

Mr Ed
Good question. I have found with the 3.73 rear, 62 mph in 6th gear is the sweet spot for the level road and a big 5th camper in tow. If the grade starts to increase, I drop down to 5th gear before the speed drops off. If I am on a road with the posted speed is 55, I stay in 5th. I try to not use 6th gear in a hard pull, it is not as strong as 5th. Also, install a tranny temperature gauge. The temperature goes way up when towing in 6th gear. Sometime I will need to drop down to 5th gear to allow the tranny to cool off.

 

I pull in 6th gear crusis control on all the time with no problems. If I get in to some big hills or alot of curves I kick it off and drop to 5th. Never thought about a temp gauge for the trans, may have to look in to that one.

 

I'd keep on doing what you're doing.

According to Cummins,if you can either gain RPMS or speed when giving it more throttle,you aren't lugging the engine.

I tow a 10K lb fiver and more often than not I'm in 6th gear when doing 55-60. If I drop down much below 1800 I'll hit 5th.

At 60 I'm running about 1950 rpms.

 

your engine, STOCK, makes peak torque at 1600 rpm. peak torque=peak efficiency. 1800 is fine. like stated above if you can still accellerate the engine at that rpm, you arent lugging.
running at 2000 or above is fine also, these B series will run at rated rpm all day long(marine engines do) however, above 2k rpm, mileage begins to drop off quickly.

 

Thanks for the responses, guys. As far as a tranny temp gauge goes, I don't believe I have a need for that (it's a manual, ya' know ).

 

If you are pulling heavy in any gear other then 5th, your manual tranny temperature will be higher then you think. It will be hard to keep the temperature below 200*. That is why they make fast coolers.