Rolling resistance when in 4WD

[Piratehunter]

1997 K2500 nv4500
this seems to have just started happening after rotating the tires. lifted the fronts up to recheck, no wobbles, wheels spin freely, no unusual movement or noise.

the truck rolls and coasts great when not in 4Hi. But when in 4Hi it feels like a brake is dragging and will hold against rolling down a grade.

It doesn’t pull to either side. when driving, it sounds like the tires are hitting those bars they cut into the edges of the road. I don’t hear for crap though, will get a friend to ride along.

any suggestions for where to troubleshoot first and second?

thanks

 

[Nad_Yvalhosert]

Same tire sizes on all 4?
Air pressures correct?
Gear ratio matches front and rear?
Front drive shaft spins? U joints arent seized?

 

[Hipster]

Gotta ask, when is it happening? 4wd is not AWD.

 

[Piratehunter]

Same tire sizes on all 4?
Air pressures correct?
Gear ratio matches front and rear?
Front drive shaft spins? U joints arent seized?

Yes, yes, yes, will look at in the morning

 

[Piratehunter]

Gotta ask, when is it happening? 4wd is not AWD.

When I shift the transfer case into 4Hi

 

[Hipster]

When I shift the transfer case into 4Hi

I meant more like on pavement or dirt. Awd has front to rear torque bias 4wd does not. Not really that uncommon in a 4wd to feel some "heaviness" when in 4wd on pavement. Given that the others things listed are in proper order.

 

[Nad_Yvalhosert]

1997 K2500 nv4500
. when driving, it sounds like the tires are hitting those bars they cut into the edges of the road. I don’t hear for crap though, will get a friend to ride along.

any suggestions for where to troubleshoot first and second?

thanks

That would be a defective bearing. First, you gotta stop using 4x4 before it seizes completely. Next, you need to find exactly which one.

I have a drive-on rack at work, one where I can jack the vehicle off the tires, but still have the springs loaded. Driving the truck in the air (without the suspension dangling is best) and listening to various points with a mechanics stethoscope is the best way to find the noise.

It should not be in the wheel bearings as they spin in 2wd, nor the CV shafts. Try the front diff and t-case forward output.

 

[Piratehunter]

checked front driveshaft this morning, rotates fine, no binding U joints, light clicks on diff and t-case sides when backlash takes up.

ok, this may have been cockpit error. Last week I parked my truck in a snowbank, on purpose, while clearing snow from driveway. backed into the snow till the rear tires spun and left it there. had pushed a mound of driveway snow in front of it, so knew I would need some front wheel assist to get out, and an excuse to play around. got in the truck and shifted transfer case to 4H with the key off. started truck and pulled onto the driveway, no issues. forgot it was still in 4h, drove to town yesterday and noted the issue. today shifted in and out of 2h and 4h a couple of times with normal results, no issues. coasted freely in 2h and 4h. I'm thinking the sequence of engaging 4h with key off might have caused the front diff actuator to not fully engage. EDIT but that starting sequence shouldn’t matter I don't know, can't reproduce it, works as expected today.

 

[Piratehunter]

I meant more like on pavement or dirt. Awd has front to rear torque bias 4wd does not. Not really that uncommon in a 4wd to feel some "heaviness" when in 4wd on pavement. Given that the others things listed are in proper order.

On pavement. I know how it feels different pavement vs dirt, but this was very different. Not happening today. Going to have a shop in town take a look at it Friday.