Commatoze

Does anyone know the recommended speed limit in 4H? I was coming home on the interstate last night with a light snow cover. When I got up to about 45 and above, there was a definate drivetrain growl and vibration, especially under a load; coast, and the noise disappeared. I have the full-time rotating driveshaft Dana 60, so if it was a U-joint, I think I'd hear it all of the time, in or out of 4H. Any guesses?

BigBlue

I'd say you found the max speed. Driving much over that in snow would scare me.

Marine

fastest I've travelled in 4WD is 65 down the freeway.
Mike

banshee

I've been over 100 in 4wd before on dry pavement... you won't hurt it. Any turning will make it growl and hop, though, and that's really hard on the hubs and transfer case.

John

Diesel-Dan

......and ya'll get sooooo much snow down there in Sugar Land! I kid, i kid.....

HOHN

Owner's manual says not to exceed 55mph. You DID read the manual, right???

Justin

gunracer1

mine has been 70 plus in 4 high many times, no problems

Marine

Manual?!?

Mike

Cumminsdude

I was taught you were not supposed to drive on like the expressway and at higher speed with 4wd engaged because something like each wheel is trying to catch up with eachother and it causes the truck to wander. I am not sure, I may be way off but thats what I was taught. I'm talking durring slippery conditions of course.

phox_mulder

Since Commatoze and I have basically the same truck stock.
(even delivered on the same day ;D)
I'll chime in.

I know with my lift, things are different, but:

Daily driving, I have a vibration over 55 that I've proven to be the front driveshaft
(removed a while back and vibe went away).

4X4 engaged on dirt roads (4H or 4L) I get a serious thunk-thunk-thunk when turning, degree of thunk doesn't change any depending on how much I have the wheels cranked, or which direction I'm turning.
Even with the front driveshaft/axles/hubs constantly rotating I don't experience this in 2H or neutral
(transfer case Neutral).

So, my theory is that under load the geometry changes and things that don't normally rub will rub.
Different stresses on different parts of the parts.

If your first thought was a U-joint it could very well be.

Now, the question of how fast.
I think you can use 4H at whatever speed the rest of the truck will stay on the road.
The manual says under 50 to protect DC from idiots that think 4X4 is unstoppable in adverse conditions.

As long as the conditions exist that 4X4 is usable (dirt, snow, mud, slick, etc) you can drive at a comfortable pace.

I think everyone knows not to engage 4X4 on dry pavement at any time, let alone try to turn on it.


phox

blackjack

The Dodge boys say 55 mph and that you can shift in and out of 4wd on the fly up to 55. Mine does not like to shift on the fly over about 45 it does not want to mesh right and I heard a grinding gear noise while trying to shift.

TomGolden

Going down the drag strip in 4HI I have reached 92.1 MPH ;D

jrs_dodge_diesel

Here is the answer to using 4x4 on high traction surfaces (roads, freeways, etc). Don't use 4x4 on high traction surfaces. Reason being, there is no strain relief for when the front end turns less than the rear end. Like in a turn. Let me explain.

When you go around a turn, one tire will turn less than the other. The outer tire in a turn turn's more as it has to travel a further distance than the inner tire. An open differential allows the tires to spin at different speeds.

Take that example and apply it to the front and rear drivetrain. When you turn, the front end travels more or less than the rear end. The front and rear end need to travel at different speeds in a turn. With 4x4 locked in everything will want to turn at the same speed, regardless of turns. Basically the drivetrain will try to keep the wheels spinning the same speed although the turn won't allow it. So what happens is the drivetrain gets put in a bind, making the thunk thunk noise Phox mentioned. When the drivetrain binds up, there is an enormous strain on the entire drivetrain. Forces strong enough to break U-joints, hubs, and transfer case's build up since there is nothing built in to allow the front and rear to spin at different speeds.

Have a nice day.

Bearfoot2

Well spoken by one who has a 2WD!!

c-hawk

I use 4wd every time i go to the track. So far no problems at all, and everything still works as well as it did when it was new. So for my truck i've been over 101mph at full throttle in 4wd. I disengage before i turn around at the end of the track.

As for the "drivetrain growl and vibration" your talking about. Mine did the same thing when it was new. After running it in 4wd for a while it went away. (Mostly slippery conditions while hunting or in snow, etc.) I don't notice it anymore at all. This sound was long gone before i started racing the truck. The truck now has 53000 hard miles on it.

So in my opinion, while a lot of things probably aren't good for the 4wd on our trucks, I think they will take a whole lot of abuse and still keep working fine.

Later,
Chris