When to lock hubs or not

[Aldercrest]

Originally Posted by oldfart3

I got T-boned at an intersection a few years ago by a subcompact about 400 miles from home.

How does a person not see one these of these beasts and then manage to T-bone it???

[Bones_GSXR]

My hubs have not been unlocked for almost 5 months. I use 4x4 everyday. Even if your hubs are locked you cannot engauge your transfercase (BW) at speeds over 50. The Atlas II is lower. So even if wet roads you can not engauge at hwy speeds.

[jage]

Originally Posted by Bones_GSXR

Even if your hubs are locked you cannot engauge your transfercase (BW) at speeds over 50. The Atlas II is lower. So even if wet roads you can not engauge at hwy speeds.

Huh? Cannot or should not? I've never had any problem although driving 65mph on sections where 4x4 is needed is not advisable, and I don't ever use it on solely wet roads, I thought they were good at any legal speed- both Atlas and OEM.

[Nomadcat]

I think you definitely can do it with most transfer cases, but it's generally good practice not to above 55. That's what my old Wagoneer manual said. Don't remember what the Taco placard said, and I have no idea about the Quadvan instructions. I usually slow down as much as I can if I'm on the highway, then shift into hi range. Anything around 55 is fine, but if it happens a little faster, it's not the end of the world. Usually.

[BroncoHauler]

Originally Posted by jage

Huh? Cannot or should not? I've never had any problem although driving 65mph on sections where 4x4 is needed is not advisable, and I don't ever use it on solely wet roads, I thought they were good at any legal speed- both Atlas and OEM.

I think he's talking about actually engaging 4wd at speed, not driving in 4wd at speed. The Atlas does need to be engaged at SLOW speed. Sometimes it takes a bit of reverse gear as well.


Herb

[carringb]

QuadVan told me they've tested driving 4x4 at high freeway speeds (like 85 or something) with no issues, not even vibration. They use CV-joint driveshafts though. They also said manual hubs can be left locked-in all winter.

[jage]

Originally Posted by BroncoHauler

I think he's talking about actually engaging 4wd at speed, not driving in 4wd at speed. The Atlas does need to be engaged at SLOW speed. Sometimes it takes a bit of reverse gear as well.

Why? I engage at speed both in the van and jeep. These aren't T-cases from 1965...

[TroySmith80]

I never understood why a lot of trucks / SUVs make so much noise and vibration at 55-65 in 4x4. What are the manufacturers doing, saving a couple bucks by not machining the gears and parts as finely as the rear axle drivetrain? Are they using cheaper / rougher components? What is different about the front than the rear? The rear could go 90 mph across the country, but try it in the front and you feel like you're in the shuttle ready for lift-off. And you get foaming diff oil, etc.

I've noticed this for sure in Jeep Cherokees, GMC Yukon, Dodge Ram, pretty sure F-350 too although it's been a little while and i couldn't swear.

[carringb]

Originally Posted by TroySmith80

I never understood why a lot of trucks / SUVs make so much noise and vibration at 55-65 in 4x4.

Often times U-joints are used for front driveshafts, and the short shaft means the angles may be too steep. CV-joints tolerate steeper angles, so they won't vibrate if used up front (or rear on a short wheelbase 4x4 that's too tall).

[Roonie]

Looking through the Atlas II manual there is no recommendation on what speed to engage the 4WD high. The only recommendation is below.
This is out of the Atlas II manual;

When shifting into 2WD or 4WD LOW, REMEMBER the following: The vehicle should be at a slow roll forward, NO FASTER THAN 5 MILES AN HOUR! Speeds faster than recommended could cause personal injury (like unloading the rear payload into the front seats!), or damage to the drivetrain (which is not only embarrassing but expensive!). The Atlas has the unique feature of 2WD low with the rear axle or the front axle. At any time while driving
in low ratio, you can disengage either the front or rear by shifting the respective handle into neutral.

AUTOMATIC TRANSMISSION; While the vehicle is slowly moving forward, place the transmission into neutral and engage the front or rear control into Low. The Atlas is a synchronized shift design, which means synchro sets have been added to SPEED MATCH the gear and shaft relation. If you are stopped with no forward motion and the unit will not shift, place the transmission in Drive or Reverse then back to neutral, then attempt to shift the Atlas.
DO NOT FORCE THE ATLAS INTO GEAR.