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The Hummer Knowledge Base
OFFROADING 101 (1 semester credit hour)
Driving a Hummer is understanding how to offroad in the first place. You need to study the terrain and pick the correct path. While we have greater clearance, more torque, better approach and depart angles than most trucks .... there is always terrain that exceeds this capacity.
With that said, I have found a steady slow throttle with RPM around 1500 to 1700 is best when stuck (sand and mud experience with TT4 so far). TT4 automatically applies the brakes to the spinning wheel, so you put power into those wheels that are not spinning. This is most effective if you are in either HL or LL. I was told that the 2000 year trucks have less efficient BTM than later models. You can still use BTM in a TT4 truck by applying a light brake and giving it more acceleration as another option.
Use tire pressure adjustments (deflate gives more surface area of tread to contact the ground), the transfer case setting (high or low lock), the transmission selection (gear selection) to help get out. You can rock forward and backward when stuck. You can go forward or backward and turn your steering wheel side to side so tire tread may catch some traction.
Like any off road truck, tough terrain (rocks, downed trees or obstacles) require low lock which gives maximum torque (lowest gearing) to both front and rear differentials. It also has higher engine rpm which results in slower mph. High lock gives you greater speed due to the higher gearing yet the differentials still get more torque than non-locked setting but less torque than LL. I use HL for greater forward or backward momentum to blast through (a running start) certain terrain .... commonly mud, snow or sand.
When all else fails, use a winch. When the winch fails to get you out, use a winch with a snatch block or multiple Hummers with multiple winches or straps. Pull out your chainsaw, cut down a tree and stick portions of it under your spinning tires. Take out your shovel, and place rocks or earth under your spinning tires.
So, always off road in the wilderness with a buddy that has a Hummer or M1 Abrams or Caterpillar .... a Jeep will not pull you out. Also, when you go over that 5 foot mound of snow in the parking lot, you can get stuck. Vehicle movement is based upon traction. No traction on all four tires or high centering where a rock or object picks up the truck so wheels do not touch Mother Earth ...... well, enough said.
Now, time for your test to get your college credit:
From what I have found with TT4 is the following....
Doesn't work in H - at all.... Works well in L and I don't think I have ever noticed it working in HL - so I don't know if it works in that gear or not
Works very well if you are already moving (i.e if you are stopped and need TT4 right away things might get a little sticky)
Just like any Hummer the RPMs should be set at 1800 and then with the TT4 truck you just aim and go, previous models you modulate the brake aim and go....
I am still figuring out how much I like the TT4, but thus far I haven't found obstacles that really annoy me due to the TT4...
The biggest downside that I have come across is that you have to be moving to get it to work. If you stop short of an obstacle and need TT4 like immediately, then as stated above, it might become very tricky....
Also, if you off-road a lot, keep an eye on your brakes, they will wear out faster then an older truck....
One tip I didn't see for TT4 owners is one that I teach. The TT4/ABS computer doesn't like varying throttle inputs when trying to figure out what to do (it's obviously not the smartest computer..). If you vary the input throttle position when trying to get the TT4 engaged, it slows down the process.
Unfortunately climbing obstacles with TT4 also means that the truck is bouncing up and down - especially with wheels spinning on loose stuff. If you slide your throttle foot back and to the right, so the side of your foot is wedged against the tunnel and just the toe of your foot is on the throttle, your foot won't bounce when the truck bounces and change the throttle position. Just hold the RPM"s in the middle of the torque band, be patient for the TT4 to wake up to the fact that wheels are spinning and your not moving forward and eventually it will kick in, apply the brakes to the spinning wheels and forward progress!
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