turn on 4wd high

mkirsch wrote:
Only problem there is that most 1/2 ton trucks haven't had locking front hubs in over 20 years in some cases. Chevy quit in 1988, Dodge in 1998, and Ford in 1997, if I'm not mistaken.

Read my post, I said "if" you have them. My F250 has them and lots of folks switch them out aftermarket.

They only time I've considered 4wd (for non traction reasons): towing up the Grand Teton pass fully loaded in my old truck.... about 10 km/h thinking that if I stop, there is no way I'll get moving again on that hill. I thought, if I am forced to stopped, 4 low should get me to the top. Thankfully, I continued to SLOWLY crawl up that hill without resorting to extreme measures. The following year that truck was replaced with my current truck.

Only problem there is that most 1/2 ton trucks haven't had locking front hubs in over 20 years in some cases. Chevy quit in 1988, Dodge in 1998, and Ford in 1997, if I'm not mistaken.

mowermech wrote:

valhalla360 wrote:
4WD High - No as others have said. You are still running at the same gear ratio so your engine will struggle just as much but there are minor differences between the front and rear gear ratios ad they likely will damage your drivetrain on a dry road. On gravel or snow, the tires can slip a little to adjust for that minor difference.

One option if you have manual lockers on the front is 4WD Low if the truck simply comes to a stop and can't get up the hill. Set the front lockers to allow freewheel and drop into 4WD Low. You won't have a lot of speed but you will have an extra low gear and since the front wheels are no longer connected to the drive axle binding won't be an issue. Don't make a habit of it as the low gearing can put a lot of strain on the driveshaft and rear diff.

While that has been done, successfully, (I even did it myself once, by accident), it is not recommended by any vehicle manufacturer, AFAIK. There is a very good chance of twisting an axle or driveshaft into two pieces. You REALLY don't want to do that!

That's why I put a warning at the end but if I'm stuck in the middle of nowhere and the rig won't go forward in the normal gear, I would likely chance it. Assuming you are borderline making it up the hill, it's unlikely fail unless you really hammer it.

HikeN2Mts wrote:
Thanks everyone. I've only used 4wd in the snow and ice or on gravel when slipping. not sure how I came up with that question, too much time before we leave for our 6 month trip.

Its OK, some probably didn't know the answer ;)

valhalla360 wrote:
4WD High - No as others have said. You are still running at the same gear ratio so your engine will struggle just as much but there are minor differences between the front and rear gear ratios ad they likely will damage your drivetrain on a dry road. On gravel or snow, the tires can slip a little to adjust for that minor difference.

One option if you have manual lockers on the front is 4WD Low if the truck simply comes to a stop and can't get up the hill. Set the front lockers to allow freewheel and drop into 4WD Low. You won't have a lot of speed but you will have an extra low gear and since the front wheels are no longer connected to the drive axle binding won't be an issue. Don't make a habit of it as the low gearing can put a lot of strain on the driveshaft and rear diff.

While that has been done, successfully, (I even did it myself once, by accident), it is not recommended by any vehicle manufacturer, AFAIK. There is a very good chance of twisting an axle or driveshaft into two pieces. You REALLY don't want to do that!

4WD High - No as others have said. You are still running at the same gear ratio so your engine will struggle just as much but there are minor differences between the front and rear gear ratios ad they likely will damage your drivetrain on a dry road. On gravel or snow, the tires can slip a little to adjust for that minor difference.

One option if you have manual lockers on the front is 4WD Low if the truck simply comes to a stop and can't get up the hill. Set the front lockers to allow freewheel and drop into 4WD Low. You won't have a lot of speed but you will have an extra low gear and since the front wheels are no longer connected to the drive axle binding won't be an issue. Don't make a habit of it as the low gearing can put a lot of strain on the driveshaft and rear diff.

jus2shy wrote:

Terryallan wrote:

HikeN2Mts wrote:
Just a question when I'm towing on mountains roads uphill I slow down of course gas engine, just wondering when I drop to around 40 or less would it help to turn on the 4 wheel drive in high mode to have the front wheels help pull?

4WD will NOT give you more power. It only gives more traction. You will be going the same speed, Just burning up the transmission as well.

To build on this post, lets say you have for example a 300 HP (at the crank) engine. Chances are, you're probably putting about 240 of thoses horses down to the bitumen due to "parasitic losses". This is energy burned due to friction in the transmission, drivetrain, churning of oils and other little things that sap horsepower. If you turned on 4WD, you'd add even more parasitic loss (you now have another differential you're spinning and putting power to) which means you're probably only putting something like 230 or less horsepower to the ground. So you've basically slowed yourself down even more.

This is neglecting what the additional stress of 4wd in the dry does, basically tearing upart or adding heavy wear to the gears and chain drive due to not having a "Slippery" surface to allow the axles to differentiate in speed a little bit.

Simple 4wd explanation here: Engineering explained - 4WD

^^^^^^^^ 110% correct. :)

Terryallan wrote:

HikeN2Mts wrote:
Just a question when I'm towing on mountains roads uphill I slow down of course gas engine, just wondering when I drop to around 40 or less would it help to turn on the 4 wheel drive in high mode to have the front wheels help pull?

4WD will NOT give you more power. It only gives more traction. You will be going the same speed, Just burning up the transmission as well.

To build on this post, lets say you have for example a 300 HP (at the crank) engine. Chances are, you're probably putting about 240 of thoses horses down to the bitumen due to "parasitic losses". This is energy burned due to friction in the transmission, drivetrain, churning of oils and other little things that sap horsepower. If you turned on 4WD, you'd add even more parasitic loss (you now have another differential you're spinning and putting power to) which means you're probably only putting something like 230 or less horsepower to the ground. So you've basically slowed yourself down even more.

This is neglecting what the additional stress of 4wd in the dry does, basically tearing upart or adding heavy wear to the gears and chain drive due to not having a "Slippery" surface to allow the axles to differentiate in speed a little bit.

Simple 4wd explanation here: Engineering explained - 4WD

HikeN2Mts wrote:
Just a question when I'm towing on mountains roads uphill I slow down of course gas engine, just wondering when I drop to around 40 or less would it help to turn on the 4 wheel drive in high mode to have the front wheels help pull?

4WD will NOT give you more power. It only gives more traction. You will be going the same speed, Just burning up the transmission as well.