4-Hi vs 4-Low
Super Moderator
Joined: Oct 2002
Posts: 8,547
Likes: 6
From: MA
4-Hi vs 4-Low
Originally posted by dassmoof
I know the difference. I'm just curious as to how 4-Low works. Does it give the wheels more torque or something? How exactly does it work?
I know the difference. I'm just curious as to how 4-Low works. Does it give the wheels more torque or something? How exactly does it work?
Rich
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
4-Hi vs 4-Low
The t-case has a planetary gearset that's engaged when you shift to low range. Like any gear, pulley, or lever, the reduction in speed and increase in force (torque) always occur together - you can't have one without the other, just like the transmission & rear axle gears.
You might find a diagram or animated CAD drawing here.
You might find a diagram or animated CAD drawing here.
Mountain Pass
Joined: Sep 2002
Posts: 181
Likes: 0
From: covington
4-Hi vs 4-Low
The transfer case in your bronco does 3 things. First it gives you the ability disengage and rengage your driveshafts. This is what allows you to switch between 2wd, 4wd, and also neutral. Te second thing is it redirects the torque so that you can drive both the front and rear driveshafts. The third which is more to answer your question is it acts like another tranny. It has 2 speeds built into it. Usually the first is 1:1 so that there is no change in driveshaft rpms and there is no change in torque to the diffs. The second is dependent upon the transfer case but is usually between 1.78:1 to 2.76:1 in stock form. Atlas makes 4:1 transfer cases that are for hardcore off roaders. So for the ease of the math lets say your low gear of your transfer case is 2:1. If your output shaft from your tranny is spinning at 200 rpms going into the transfer case then the gearing reduces the rpms of the driveshafts to 100 rpms because the input shaft spins twice to each output shaft revolution. The speed is cut in half but the torque is doubled. So if before the transfer case there is 200 ft/lbs available there is now 400 ft/lbs coming out of the tansfer case. THis is why in low gear you can pull steep hills with very little throttle, but it doesn't get there very fast. .
