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shifting into 4wd

mjager

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mjager Enthusiast

mjager

Posted
Posted

I have an 07 classic GMC, and have read the manual. But it's still not too clear to me about shifting into 4L and back, manual says to be in neutral but at less than 3km per hour?

 

Does that mean you should be rolling very slowly and have the tranny in N?

 

What's the best way based on real world experience ?

Ranger Senior Enthusiast

Ranger

Posted
Posted
I have an 07 classic GMC, and have read the manual. But it's still not too clear to me about shifting into 4L and back, manual says to be in neutral but at less than 3km per hour?

 

Does that mean you should be rolling very slowly and have the tranny in N?

 

What's the best way based on real world experience ?

 

 

 

 

Well, the easiest way is to stop the truck, shift to neutral, then engage the 4-LO. Works every time for me. They only recommend moving "slowly" (which is near impossible really, by the time the computer sees that it's moving below x amount mph the truck would've stopped) because it's SLIGHTLY easier to engage the front hubs if they're rotating.

srlbotanical Enthusiast

srlbotanical

Posted
Posted

I usually roll slow when shifting into 4L. When I had the manual T-case, I had to be rolling a little or my gears wouldn't mesh. I have the electronic T-case on my 97, and it seems to do best when I am rolling real slow.

 

Try it a few times on level grass or gravel to see how your truck acts. You will always get a good clunk when shifting in and out of 4L, at least in my experience. 4H shifts nice and quite, but it clunks into 4L.

 

Steve

COP TZR Enthusiast

COP TZR

Posted
Posted

My transmission guy does all work for GM recommends you...stop, put in park,turn ignition off, shift into 4L, restart engine. Common to bend shifter fork and ruin bushings in transfer case doing otherwise.

WindyCityPilot Enthusiast

WindyCityPilot

Posted
Posted
My transmission guy does all work for GM recommends you...stop, put in park,turn ignition off, shift into 4L, restart engine. Common to bend shifter fork and ruin bushings in transfer case doing otherwise.

 

 

 

 

Anyone else tried this? Seems to me having the engine on or off wouldn't make any difference...unless I'm missing something. If it works then I'll definately give it a shot...just curious if anyone has tried this?

 

Also what is that large clunk when it engages 4-LO? Sounds like the transfer case is going to grenade all over the road!

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted
My transmission guy does all work for GM recommends you...stop, put in park,turn ignition off, shift into 4L, restart engine. Common to bend shifter fork and ruin bushings in transfer case doing otherwise.

 

 

 

 

GM doesn't recommend ALL that.

 

The idea is to engage with as little clash and clunking as possible, in my case it is traveling about idle speed, put the transmission in neutral, then apply brake as needed to slow the vehicle to a very slow roll. Then press the 4 lo button while maintaing that very slow roll. If I engage it while stopped it clashes trying to line everything up.

 

Similar method works on my Dad's manual T-case.

WindyCityPilot Enthusiast

WindyCityPilot

Posted
Posted
My transmission guy does all work for GM recommends you...stop, put in park,turn ignition off, shift into 4L, restart engine. Common to bend shifter fork and ruin bushings in transfer case doing otherwise.

 

 

 

 

GM doesn't recommend ALL that.

 

The idea is to engage with as little clash and clunking as possible, in my case it is traveling about idle speed, put the transmission in neutral, then apply brake as needed to slow the vehicle to a very slow roll. Then press the 4 lo button while maintaing that very slow roll. If I engage it while stopped it clashes trying to line everything up.

 

Similar method works on my Dad's manual T-case.

 

 

 

 

 

I've tried the slow roll way of going in to 4-LO and i still get the clank. I've tried it stopped with the engine running and get the clank....just trying to figure out if there is a way for me to not get the clank going into 4-LO.

lagrange151 Enthusiast

lagrange151

Posted
Posted
there are several reasons to shut vehicle off to change...no clang...shifter fork is very easy to bend and is mounted on plastic bushings....

 

 

 

 

Just curious why shutting the engine off stops the clang noise?

 

 

 

 

 

 

there is still a little bit of motion being passed thru the trans in neutral due to internal drag

Ranger Senior Enthusiast

Ranger

Posted
Posted

Either I've got an oddball transfer case or I'm just not hearing it, but I don't notice any loud noises while shifting into 4-LO. I've had the windows down and radio off when I put it in low range but I can just barely hear a "thump" coming from the front as the axles engage.

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