emptyd

Hey All,

This should inspire some discussion, or perhaps even dispell a few myths?

What is/are the risks associated with exceeding the max. factory recommended speed while in 4HI on say; a freeway? I assume this would only affect the non full-time 4WD 4Runners.

Any thoughts?

Matt

Darren

There is no discussion to be had.

There is no risk for those with the full-time system in any circumstance and no matter the speed, as they are AWD when the center diff is unlocked.

The part-timers, including your 'Runner, should never be in 4WD on the freeway, period, as you don't have a center diff and you will get drivetrain binding causing undo stress on stuff, and possibly, potential breakage at some point. You only have a max speed to engage 4WD, but once in it, feel free to go faster. Though at that point, there isn't a need to be in 4WD to begin with.

emptyd

Darren,

I knew this would be a hot topic. You are absolutely correct...the full timers - no problemo. Part timers (like me); "engage at low speed"; YES, "no max speed"; NO(?). Toyota recommends under 60. - Why?

Let's say for the sake of argument, it's winter and you live in No. California or Orego/Washington Metro - Lots of rain, lots of oil on surface streets and freeway onramps, etc. etc. This is likely a good time to consider 4HI - Yes?

Mostly straight, so no drivetrain bind. Why the 60 Limit? I personally have NEVER followed the 60 limit in 4HI. So far, in the 67,000 miles I've put on my rig since new - no issues. YET.

Hmmmm...any further thoughts?

Matt

4RunnerFever

I thought the max speed to SHIFT into 4 hi was 50 mph. Then the sky is the limit.

Churnd

I drove 40 miles on the interstate in 4-hi once. It was winter and we had just had a big ice storm. The entire road was iced over completely the whole way. I never went over 45 mph. I think it was safe to do because of the lack of traction. I never felt the truck loose traction, but living in MS and not having experience driving on snow/ice made that one of the nerve wracking experiences I've ever had.

AgRunner06

I'm am 100% sure that is correct. In my owners manual it says the top speed for 4HI and 2HI is 103 mph. You just have to be under 50 when shifting.

Memphis4X4

I have shifted into 4Hi at +60mph frequently. I knew that Toyota had specified a max speed limit to shift into gear and I assumed it was to assure synchronization of the drive trains in the transfer case. However, I have not seen any problems in the +180K miles on my truck.

Now as far as the point of not needing 4WD on the freeway.....I beg to differ. Here in the mid south, we get a lot of rain, sleet, ice, and a little snow......all of which cause slick conditions. Now, I know 4WD will allow you to start from a stop in slick (limited traction) conditions but it will also provide added stability when 'going in a straight line' as well. For example, I lock into 4Hi every time it rains. We get torrential rains and these tend to make the freeways hydroplane arenas. I have seen many cars hit deep puddles and spin. I use the 4WD to give me the traction to negotiate through these puddles and stay in control. I would rather have 3 wheels providing traction rather than the one while in 2Hi while plowing through a puddle. Likewise, when slowing in limited traction situations, the 4Hi provides control....granted it doesn't provide "4 wheel stop" but it sure keeps the rear end from rotating around when slowing down. Since we have some of the worst drivers here in Memphis (people here consider the streets as a profit center and a source of income), I'll take as much control as I can get to keep my Runner away from others.

Just my personal experience,
David

Flygtenstein

Why?

I see no legitimate reason to be over 25 +/- in 4wd. If you can go faster than that, you likely don't need 4wd.

Glenn

I have shifted into 4HI at 75 mph with no problems whatsoever. As long as you are not really on the gas, it won't hurt anything.

I have driven over Snoqualmie Pass in Washington State in the wintertime many times. I would usually shift into 4HI at Milepost 47 or so, depending on the conditions. I would leave it in 4HI sometimes until I got home, another 60+ miles. It would just depend on the conditions of the roadway. I had to drive 75+ mph in 4HI for a while because I didn't want to be driving much after dark. There was no binding of the driveline. It would shift in and out of 4HI very easily.

It really boils down to how well you know your vehicle and the conditions of the road. There are no "hard and fast" rules that apply for all situations.

Glenn

To give yourself an extra margin of traction. If the Toyota 4wd system could not handle anything over 25 mph, then there would be no reason to have 4HI. Particularly with trucks that don't have a lot of weight over the rear wheels, the added traction afforded by engaging the front axle can help to avoid spinning out.

Memphis4X4

Well said.

That is what I tried to get across in my post above.

calrockx

i thought the manual said it's okay to shift into 4wd up to 62mph, but 50 is a good rule of thumb anyway. tho i've never gone above 30 in 4wd, i guess i can see times where doing so might be valid, like on a slick, icy road say.

to clarify...so as long as my center diff is unlocked it's okay to go fast in 4wd? i've only locked a few times just to get rid of vsc when offroad.

4RunnerFever

CalrockX - I'm pretty sure the computer will unlock the center differential if it detects a situation it doesn't like.

mtnfreak

I'm often faced with this choice:
1) Creep up the snowy, icy, sanded on-ramp at a safe, decent speed and get dead when I try to merge into 75+mph traffic at 25mph.
or
2) Go into 4Hi and get as much speed as possible on the snowy, icy, sanded on-ramp so that I at least have some momentum in my favor when somebody runs their H2 up my arse.

And back to the original topic - I go in & out of 4Hi at all speeds and have been over 75mph several times before I realized that I forgot to shift back to 2wd.