4 wheel high vibration

[Frankie945]

Anyone else notice any vibrations when they use 4 wheel high or 4A. Since the snow I haven’t used 4 high or 4A till last night on the interstate and I noticed right away it has some vibrations. When you let off the throttle they go away it’s only when your on the throttle. When I reached my destination I reached up under the front and felt the bottom of the front diff through that little opening and it wasn’t warm at all. First I thought it might of been the ring and pinion not properly meshed right. Thinking now it could be the front driveshaft being out of balance. Something making it not feel right.

Also I think 4A is just marketing BS because it’s just 4 wheel high there doesn’t seem any difference between 4high and 4 auto.

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[VelocityBronco]

Mine does this too...just thought it was how it was supposed to be? That is not normal for a 4x4?

 

[WuNgUn]

Anyone else notice any vibrations when they use 4 wheel high or 4A. Since the snow I haven’t used 4 high or 4A till last night on the interstate and I noticed right away it has some vibrations. When you let off the throttle they go away it’s only when your on the throttle. When I reached my destination I reached up under the front and felt the bottom of the front diff through that little opening and it wasn’t warm at all. First I thought it might of been the ring and pinion not properly meshed right. Thinking now it could be the front driveshaft being out of balance. Something making it not feel right.

Also I think 4A is just marketing BS because it’s just 4 wheel high there doesn’t seem any difference between 4high and 4 auto.

Isn't the front drive shaft always spinning, just disconnected at the transfer case?

 

[Coldsmoke]

Anyone else notice any vibrations when they use 4 wheel high or 4A. Since the snow I haven’t used 4 high or 4A till last night on the interstate and I noticed right away it has some vibrations. When you let off the throttle they go away it’s only when your on the throttle. When I reached my destination I reached up under the front and felt the bottom of the front diff through that little opening and it wasn’t warm at all. First I thought it might of been the ring and pinion not properly meshed right. Thinking now it could be the front driveshaft being out of balance. Something making it not feel right.

Also I think 4A is just marketing BS because it’s just 4 wheel high there doesn’t seem any difference between 4high and 4 auto.

Mine operates fine with no vibration in either 4A or 4H. I use 4A quite often when it snows or I am on dirt trails.
BTW, if you want to see the difference between 4H and 4A, just try each on dry pavement while making a sharp turn. 4H will buck and bronc. 4A will turn as expected.

 

[L8apex]

Also I think 4A is just marketing BS because it’s just 4 wheel high there doesn’t seem any difference between 4high and 4 auto.

4A is either 2H or 4H. It just automatically switches between the two based on slip conditions.

So if driving in the snow it probably detects enough slip that it would be 4H most of the time.

Think of 4A as good for greasy conditions where you may unexpectedly lose front end grip; you'd be driving along in 2H - front end starts to slip, boom, you've got 4WD

 

[L8apex]

Isn't the front drive shaft always spinning, just disconnected at the transfer case?

Yes...until 4WP gives us some more information on those locking/free wheeling hubs...

 

[Julz670]

One of the displays in the instrument panel shows power distribution. If you look at that while driving in 4A you'll see that when you are just cruising in a straight line on dry pavement, power is only going to the back wheels. When you accelerate or corner, it will send some power to the front wheels as well.

 

[Frankie945]

When it’s in 4 high it shows the same power delivery on the dash as it does in 4a. It’s a open diff till you lock the locker so if it’s not locked (which it can’t be) it should have zero to do with turning making a difference rather your in 4h or 4a. I think4a is a gimmick unless someone who actually engineered the thing gets on here and explains what it actually does.

I’m not sure how this transfer case works but your right the front shaft always turns because the hubs are always locked unlike a manual lock out front axle. Something is making the vibration and it changes depending on the load. Least it does when your on asphalt. It’s been several years since I had my jeep but I don’t remember any vibrations when I used 4 high when the jeep was in stock form. Maybe I’m over thinking this and it’s normal I just know I was ready to go back to 2wd soon as I could because didnt like the feel of those vibrations I could even hear them too.

 

[VoltageDrop]

4A is either 2H or 4H. It just automatically switches between the two based on slip conditions.

So if driving in the snow it probably detects enough slip that it would be 4H most of the time.

Think of 4A as good for greasy conditions where you may unexpectedly lose front end grip; you'd be driving along in 2H - front end starts to slip, boom, you've got 4WD

No, in 4A the clutch in the transfer case can send 0 to 50% of engine torque to the front axle. In 4H, the front axle is coupled directly to the rear so it's always 50%.

In a 4A Bronco the front drive shaft always spins but that might not be true with the basic transfer case because the wire diagrams show a front axle disconnect.

 

[Frankie945]

Well I must always be on ice or sand because in 4a according to the power delivery gauge all 4 tries are getting power all the time.

 

[PWillette]

Well I must always be on ice or sand because in 4a according to the power delivery gauge all 4 tries are getting power all the time.

IMO there shouldn't be any vibration in 4H or 4A, I'd be having the dealer take a look.

 

[iwantabasebronco]

Did you shift on the fly or shift at idling speeds?

 

[Frankie945]

i did both fooling around with it trying to troubleshoot myself.

Did you shift on the fly or shift at idling speeds?

 

[iwantabasebronco]

i did both fooling around with it trying to troubleshoot myself.

Got it.. I was gonna suggest trying the opposite of whatever you did initially but you already did!

 

[Julz670]

Well I must always be on ice or sand because in 4a according to the power delivery gauge all 4 tries are getting power all the time.

You are correct in that most of the time power is still being sent to the front, but I've definitely seen mine only sending power to the rear in 4A. I'm no expert, but I don't think Ford did a great job programming 4A. It seems to have nothing to do with slip and more to do with driving style. Any sort of acceleration or deviation from steady and straight seems to send at least some power to the front. Not that it's a bad thing really, just unnecessary 95% of the time that it sends power to the front. You pretty much gotta drive like my granny to get 4A to only use 2H. Not that any of this helps solve your vibration problem.

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