Maxout05

Haha yep and you never get used to it either, lol! Some day santa will bring and install me some *** end lift!

Keeblerz28

http://www.motorcraftservice.com/pub.../08f12og1e.pdf ~around page 284 of the pdf

My 2008 F150 owners manual, directly copied:
'In the Electronic Shift 4WD section

"2H (2WD High) - Power to the rear wheels only; used for street and
highway driving. Provides optimal smoothness and fuel economy at high
speeds.
4H (4WD High) - Used for extra traction such as in snow or icy roads
or in off-road situations. Not intended for use on dry pavement.
4L (4WD Low) - Uses extra gearing to provide maximum power to all
four wheels at reduced speeds. Intended only for off-road applications
such as deep sand, steep grades or pulling heavy objects. 4L (4WD Low)
will not engage while the vehicle is moving above 3 mph (5 km/h); this is


Shifting between 2H (2WD High) and 4H (4WD High)
• Move the 4WD control between 2H and 4H at any forward speed up to
55 mph (88 km/h).

Note: Do not perform this operation if the rear wheels are slipping.
Note: Some noise may be heard as the system shifts or engages; this is
normal."

So it says you can to switch between 2wd and 4wd at any speed up to 55mph.

Northeast, I don't think running at 60 would hurt it too much, although I wouldnt attempt any faster.

I don't totally agree with you on this, bluescrew. True, 4wd doesn't help you stop any better but it does help you turn more controlled without drifting (for lack of a better word) by having the front wheels helping to pull your truck in the desired direction. 4WD can also aid at highway speeds, for example, the highways here are plowed, but only certain parts are down to visible pavement right now. In 2WD under load, (driving up a hill) the rear end may kick out due to lack of traction on the halfway snow-covered road surface leading to loss of control, accident, ... you get the idea. In my experience, this may be avoided in some cases by staying in 4WD under these road conditions. That said, always drive at a safe speed for your own road conditions. When the pavement gets drier and clearer in certain sections, I will drive in 2WD in those areas and 4WD for the areas still half snow covered. That's what the electronic-shift 4WD is for

Franchi

I go about 45 as if the 4x4 is engaged, it's nasty out.

blankline9

This is funny but what does it have to do with the question of a top speed for 4hi?

Thislilfishy

Good point...

I ran my little Liberty in 4Hi all the time in the winter (Northern Ontario) at highway speeds with no issues. I also found stopping was greatly improved as it didn't have ABS. With 4 wheel drive engaged it would prevent one or two wheels from locking up when braking. I would say the effect would be similar with abs. That said, the jeep developed an odd vibration over 110Km/Hr (68 MPH). So I usualy keep the truck under that speed and have had no problems at all. I travel approx. 100,000 Km/year (62,000 Miles) and never had transfer case issues (work vehicle). Considering the weather up here, it's safe to say that about 30% of that mileage was in 4H. Although I smoked a few tranny's, but that was an unrelated issue and a long story.

Although the manual says you can engage 4H under 55mph, I find the truck really doesn't like switching on the fly (both my '06 and '08) and so I usually determine if I need it before leaving the driveway. I've never had issues taking it out of 4H on the fly though.


Ian

Quatsino

Think about the 4WD transfer case from a mechanical engineering standpoint...

An automatic transmission (even though extremely complex) is designed specifically for longevity and full time use - all of the mechanical elements are all in close proximity to a central flow of power through the unit. This means that even if the rotational speeds are high the actual forces on the mechanical bits are minimized. It is easy to lubricate this type of a system without breaking down the oil.

The transfer case, on the other hand, is physically large and has mechanical elements located relatively far away from each other. It has a primary shaft which flows power via a planetary gearset through a relatively long HyVo-style chain to a secondary shaft. The aluminum case itself is an important structural component. (Think about stresses of 2 shafts trying to be pulled together by a chain within the case).

It is harder to lubricate this type of a system - especially a chain made of a gazillion individual small pieces - at high speed. The lubricant is ATF which is a highly complex 10 weight petroleum oil - very light indeed. The transfer case is designed to be used part-time which means that it is not designed to be as durable as the engine, transmission and front/rear ends.

Even though not specifically stated anywhere, being sympathetic to the above picture should indicate that the rotational speeds and various forces within a stock transfer case have a limit - somewhere - a compromise between longevity and absolute strength.

In my opinion, 60mph is about as fast as you would want to go in 4Hi and still feel secure that excessive transfer case wear is not occuring.

loneacre

I live in mich u.p. and i do alot of winter driving. When snow gets to be acouple -three inches i'll slow down to 50 then put it in 4h then travel 60 to 65 mph. I've had no proplems yet. 94000 on my 04 xlt. It handles alot better than in 2wd

loneacre

Forgot Ialso carry 250 lbs in the back which means alot.

northeastFX4

Its because he said something to the effect of being irrational while driving in snow, and i pointed out to him that I live in northern maine which is mostly just snow so im used to it, and he pointed out he does some training for the army in new york.

northeastFX4

Another huge reason why i kept it in 4wd...the roads are twisty and it keeps the back end from coming out all the time.