jeffcall7

I have a 10,500 lb, bumper pull camper I pull with my 2006 Quad Cab Long bed 4x4 AUTO with the 5.9.

When I first start to get the thing moving up a slope or out of grass ruts the revs on the engine need to go into the higher 2000's or even 3k to get it to start going, then I can let back up on the pedal and keep it going... this is in 4 Hi (Lock) or 2WD. In 4 Lo however, the truck pulls it like a TANK. And I mean a TANK ON CRACK. No hesitation... it will pull the camper out of a ravine in the bottom of a ditch and up a 50% slope just at idle! (Just kidding for emphasis). I never noticed the difference when I had my old 6000 lb camper.

I assume this is normal? I don't know much about how these engines/trannys are set up. But what exactly allows the truck to have that much awesome direct power in 4 Lo but then lose it and feel 'muddy' or disconnected from the tranny in 2WD and 4 Hi? Is it the torque converter or something else? Is there something I can change to make it pull better in 2WD (other than jacking the HP up with thousands in engine mods or a programmer)? Lastly, am I damaging anything by manuvering around my tight-*** yard to park the camper in 2WD or 4 HI revving the engine like that through 5-7 maneuvers while the truck takes so long to start rolling - will I burn up the torque converter?

THANKS!

pdogg

I can't talk about the Torque converter, but I can say the 4H and 4L differences is your 2-speed transfer case. When you put your truck in LOW gear, it changes the transfer case gearing.

that's why you're seeing the power change..

basic 4x4 stuff here..

SOhappy

Pretty typical. Many CTD owners choose to put it in 4 low to maneuver heavy trailers on hills at low speeds..

Probably better for your tranny (and converter), but if you're turning sharp on grippy surfaces you're stressing everything else in the drive train.

Only locking-hubs will give you the best of both worlds.

.boB

The transfer case has two ratios: low and high. By shifting into low, it's like suddenly changing your rear differential ratio from 3.50 to 4.56. It dramatically increases torque application to the ground. Like applying a longer lever to increase torque.

jeffcall7

So... then if I do an automatic to manual hub conversion I can still set the selector switch to 4 LO in the cab but not lock the hubs at the front wheels and I'll have the extra power/torque without all the strain on the driveline, etc. from tight turns on non-slippery footing? Would there still be binding up across the rear axle or does the rear diff not lock on my truck in 4 LO?

Sorry - I have had 4WD vehicles my whole life but have never thought about it this much.

MulesDiesel

your correct, having unlocked front hubs while in 4low will allow the tight turns without binding. and no the rear diff does nothing different in 4low or 4high

eastmentCTD600

Incorrect. The transfer cases in our Dodge's have a 2.73:1 reduction in 4LO. Thus the torque output of the motor is multiplied by 2.73 compared to Hi range.

If you want to use the above "changing rear differential ratio" example it would be like going from a 3.73:1 in HI range (assuming you have 3.73 rear end) to a 10.18:1 in LO range.

I believe the engine is torque output limited in LO range to avoid damaging the drive train, i.e. they reduce the output of the motor to a certain level to avoid damage.

They are tanks in LO range.

.boB

I picked those numbers out of the air as an example.

SOhappy

Yup. No binding on rear axle in 4 low if the hubs are free.

(...and you don't have automatic hubs, they are always locked. Front axle and prop shaft turn whenever the front wheels are in motion.)

jeffcall7

so then the disconnect from 4WD to 2WD occurs where? The transfer case? or at the front axle? I knew the front axle was live and always turned but I always thought the engagement of the 4WD was at the hub like on all my previous trucks (all Fords.... sorry... I know.... but I've moved on to bigger and better trucks now)

SOhappy

The disconnect occurs in the the transfer case. Just like driving around with your hubs locked all the time.

Oh well at least everything stays lube-ed, and surprisingly it only costs about 1 mpg according to most who have gone with free-spin hubs.