I know you normally don't have a need for 4wd at high speed...at least I can't think of any scenarios in which you'd need it....but IS there a max speed for 4-hi?
4hi is nice because you can go in and out on the move. You have to stop to get to 4lo.
I would use that all the time in my past 4wd's when it was snowing around here.Not all roads where the same conditions. One could be well plowed and treated and the next untouched. Being able to go in and out of 4hi as I go is nice.
Also in my ramcharger and XJ with the gearing thing was SCREAMING past 25-35mph in 4lo. I am a new JK owner but I don't expect it to be much different.
theoretically you could go as fast as you wanted-- in 4 hi the transfer case is in a 1:1 ratio so as fast so there is no gear reduction-- now since the hubs in a jeep are always "locked" meaning the front differential and axles are always spinning at the same speed as the rear-- when you shift into 4 wd the only thing that happens is the axle couples together and the front drive shaft and transfer case apply power--so theoretically the limit would be the same as in 2 wd.
That's sort of what I was thinking, but I wasn't sure. It's raining hard here today with 2"-3" of water running across some roads. I used 4wd on the way to work this morning for the first time since I got the Jeep in May. That's what got me thinking that way, even though I never topped out above 45 mph.
Theoretically, there should be no limit. Practically, however, if you truly need 4wd, then you shouldn't be traveling very fast. The only time I use 4wd at any speed beyond about 25-30 is on very sandy roads, or ones with really deep two-track grooves, where the front axle driving with the rear adds to stability. Even then, I wouldn't typically drive beyond about 40 under any circumstances.
I've wondered about how fast you can go in 4HI, but never asked because there's always too many responses of "you shouldn't be going fast if you need 4HI anyways". Sometimes you just want to know what you can do.
Use it all the time on snow covered roads (4Hi), but typically not exceeding 50mph at maximum and try to be going < 30mph when shifting in/out on the fly.
I would think that one of the big issues to be concerned about is: say your traveling at 60mph on snow/water covered roads in 4hi and suddenly you have a bend in the road with clear/dry pavement. Your going to experience some pretty bad wheel hop there if you dont get your Jeep out of 4hi there, right?
When in 4hi on a slippery road in a turn if you let off the gas you might get some engine breaking which will pull you into understeer. Fix is bump shifter into neutral or open the clutch through the turn for maximum traction. This only matters within probably 10% or so of your traction limit and obviously starts to matter a lot more at speeds over 55 on slippery roads because you reach that threshold very easily. Otherwise 4hi is fine
Handling suffers when traveling high speed in 4-HI. Your normally freewheeling front tires are now contributing driving force, and there are a lot of spinning shafts and such that contribute a gyroscopic effect that you have to overcome to make a turn.
For example.. take a bicycle wheel, spin it, and hold the axle. Then try to turn it.
Handling suffers when traveling high speed in 4-HI. Your normally freewheeling front tires are now contributing driving force, and there are a lot of spinning shafts and such that contribute a gyroscopic effect that you have to overcome to make a turn.
Makes no sense at all, everything is spinning 4x4 or 4x2 no difference... and at high speed you MORE stable with 4x4 on winter covered roads... I drive on frozen lakes at over 70mph in 4x4 often... 4x2 would be scary
I always go 4HI on snow covered highways and fast gravel as fast as 60mph. In 2HI there is practically not much control at that speed in those conditions.
Practically, I always go 4HI at any speed and on any kind of surface that is not clean asphalt.
Engine braking has a greater effect in 4wd - now you have 4 wheels slowing you down instead of 2.
Mine is an auto, but on slippery surfaces (ie. snow) I use the stick shift to control my speed more than using the brakes. One can argue this is transmission braking not engine braking, but they actually add up.
Exactly. The whole point of this thread was speed guys. It doesn't matter at low speed sure but this thread is all about high speed. ......:tomatoes:.... Context people...
If you find yourself in a understeer situation that could result in a crash simply get into the throttle, especially in dirt. Or so I read on the oll interwebs
I'm reading this thread and wondering if any of you actually know how to drive a 4X4 vehicle?
I grew up in Illinois, 4 wheel drive come naturally to us.
We drove at all speeds under all conditions whenI grew up on the farm.
As teens we didn't always just drive 45 mph off road.
We also had US 66 covered with snow and ice to drive on...
If you need 4 wheel drive use it and drive as fast as your skill will let you .
I strongly suggest no one follow this advice. Your own estimate as to your ability to control your vehicle at speed in slippery conditions is likely grossly overestimated.
On less-than-ideal surfaces, the line between feeling in control and actually being out of control is quite fuzzy and unpredictable. If you want the opinion of an expert, ask any NASCAR driver. Or any sprint car driver.
This is pretty funny actually. The thread isn't about driving at high or low speeds in 4wd. I was simply curious about the mechanical limitations, if any, that speed places on the 4wd system in the Jeep.
In reality, there is no specific speed where good turns to bad. The faster you go, the more wear and tear on the components, and the greater the chances of losing control, which can be VERY bad for the Jeep. There really is no other way to answer your question, in light of what you're looking for.
Seeing that it's a message board with lots of moot points like, "what's better? Rhino or Hyper green? or manual vs auto?", I don't this this was a bad thread compared to those.
one scenario where it maybe helpful is say a rubicon with its very low 4.10:1 on longer drives on sand and a manual trans. On some soft sand with no perpendicular troughs you would be spinning wheels a bit faster than your actual speed and you would want to be maintaining a decent speed. say running at 20 mph and spinning at 25mph
Virtually everyone I know with a 4:10 and manual is up in 4-high on ling beaches. if you watch the guys in Australia on the sand on youtube they are usually in 4wd high
This all sounds like the making of an episode of Mythbusters.
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