long drive in 2-lo?

[kluther]

i just purchased the B/D 2-lo kit . Is it ok to drive 4-5 miles up a steep incline 8-10% pulling a 12,000 lb trailer? ken

 

[Snow man]

I have plowed for 12 hrs in 4 lo,driven over 50 miles straight in it,and the truck weighs about 10500-11000 while doing this. By using just the rear axle I cant see why you would have any trouble at all.

 

[Loren]

Ken,



I would use 4-low instead of 2-low. I also have a very steep hill leading to my house. When towing, I climb that hill, with its bends, in 4-low. The curves are mild and don't cause any problems with using 4WD.



The problem you may have with 2-low is because the transfer case has a 2. 72 low range ratio. That means that the torque downstream from the transfer case is multiplied by 2. 72. The truck is designed to prevent you from sending all that torque to only one driveshaft. It is normally split between two drive shafts when in low range.



By installing the 2-low kit, you will now override that protection. If you are not VERY careful, you could easily break a u-joint or twist the rear driveshaft into a barberpole. With luck, these would be the parts that fail. If you are not so lucky, you could break an axle, or some part in the differential.



Again, I recommend using 4-low.



Loren

 

[jlhartak]

You didn't say if the hill is paved or not? If it's paved I would not use 4LO. 8-10% is a good grade but the cummins should handle it easily in 2HI low gear in the trany, just keep the rpm up a bit and shift the trany into low so it doesn't upshift if you let up a little. If it's a matter of not being able to go fast enough to keep the trany temps down then use 2LO with very easy throttle inputs to limit the shock load on the rear driveline.

 

[Deezul1]

I agree, if its not paved, 4low. Otherwise 2low is ok but be careful with throttle, pretend there is an egg between your shoe and the pedal. There is a real chance of twisting something off if you get crazy with the go pedal otherwise it should work fine.

 

[kluther]

it is paved (concrete). trans temp will sky rocket on that long of a grade in second gear, with 95 + degrees outside temp. i thought the drive line would bind if driven that long on concrete. ken

 

[Loren]

Ken,



Yes, the driveline will bind up if there is no slippage at the wheels and the curves are tight enough. This condition can break something. However, driving in 2-low can also break something.



My hill is paved and has some curves, but they are mild and I can use 4-low without any problem. If I had experienced binding, I would have to use the long way around that doesn't involve such a steep climb because neither of my trucks has a 2-low feature.



Deezul1's suggestion to use 2-low and drive VERY carefully is a good one. Don't punch the throttle or you could easily break something.



I often drive on pavement in 4WD. If it's wet and slippery, I will often shift into 4-high and drive on. I have rarely experienced binding in the drivetrain. It's very obvous when it happens, and I could probably just power through it, counting on the tires to slip. So far, I have gotten away with this technique, but it may not work forever.



Driving in 4WD creates slipping forces at the tires. If the road bends gently right, then left, then right, etc. , these forces do not build up sufficiently to cause the drivetrain to bind. A sharp turn, however will bring me to a stop, or cause skidding of one or more tires.



The friction force between the tire and the pavement depends on the coefficient of friction (gravel is lower than dry pavement, for example) and on the weight the tire is carrying. If your truck is heavily loaded, on dry pavement, in 4WD, and turning, you could be in trouble.



Loren