99 Sierra Nbs

[JJP442]

Hello All,

New to this forum, been lurking for a bit.

Over the summer I picked up a 1999 GM Sierra Ext Cab (NSB).

The truck has 170k and runs awesome.

Winter came a few days early to the East Coast so I put the 4WD to work.

Although it is operational and I do not have any 4WD service lights illuminated, the truck really seems to be laboring when in 4WD.

I can feel & hear a faint grinding/humming when the 4WD is engaged and it kind of jerks a tad when making turns.

It also appears to want to slow down. (doesn't roll as easy)

I have not serviced the 4WD system on this truck.

I'm not entirely sure what is involved in a 4WD service and don't know who to trust to do it correctly.

I do not want to be at the mechanics mercy not knowing what is up.

I'm hoping my 4WD issues are nothing major.

BTW- it has the push button 4WD system.

It appears to be working properly.

 

Thanks in advance,

Big John NYC

[Jansen]

Big John,

 

That sounds like normal operation. You will always get slow down as the front axle has been engaged and puts drag on the system. Turning will tend to jerk and skip/hop due to wheels trying to turn at different speeds but not being able to.

 

Jansen

[rodram]

Big John.... yes... the description of your 4wd operation sounds normal...

 

some advice though... do not drive in 4wd (high or low) on dry or wet pavement ... only use the 4wd if you are on snow, ice, loose gravel, etc. that will allow a little give on the wheels when you are trying to turn (... to avoid stress on the 4wd parts while it is bucking or jerking around a corner...)

 

the transmission and transfer case are trying to drive the front and back wheels at the same time/speed, so in order to turn a corner, something has to give, and if you are on snow or ice you won't even feel that, but on pavement everything is going to fight you when you try to turn.