4 wheel drive

84'GMC4x4

LawnSite Member
Location
MA
just a few days ago i put my truck in 4wd for the first time since last winter. it seemed to drive alot smoother after i did. usually i have to rev it up pretty good b4 shifting or else it seems to have a little trouble pulling the next gear. in 4wd however, it pulls right along nice and smooth. so i would like to keep it in 4wd all the time.
my question is that i have heard that it is not good to drive on dry pavement in 4wd. does this only apply to 4 low? or is it 4 high as well? what damage will this cause?

also, when i turn the wheel fully in 4wd while driving at low speed it kind of jumps along. any ideas what is causing this?

Greg
 

MTCK

LawnSite Senior Member
Location
Idaho
Axle wrap is what you're feeling when you turn sharp and you're going slow. Around a corner, all 4 tires want to go a different distance, since they are taking different paths. In your part time 4x4, there is no differential between the front and rear axle's so it sorta "hops" or breaks traction at one end or the other to compensate for this. You don't feel it as much when it's really slick, because one of the tires will sorta skid and compensate smoothly. This is also why it's bad to drive on dry pavement, in 4 hi or 4 lo with your truck. In the 70's, lots of chevy's came with full time 4 wheel drive behind the automatics, but yours should have the NP208 T-case, which is a part time unit. So, to sum it up, yeah, it's not good to drive on dry pavement in 4 wheel, and it's the lack of a differential between front and rear axel's that you're feeling when you turn sharp at low speed. Hope that helps.
 
OP
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84'GMC4x4

LawnSite Member
Location
MA
MTCK, mine is an NP208. did the full time xfer cases have some type of dif in them to stop this hopping?

Greg
 

MTCK

LawnSite Senior Member
Location
Idaho
I believe so. I've never had one, but the NP203 did I believe, but you could still lock it. I'm not sure if it was an actual differential or a set of clutches. I'm sure one of these guys with the older trucks could help you with that one.
 

John DiMartino

LawnSite Silver Member
Location
Walden,NY
Keep your truck in 2wd,drivetrain bindup is what your feeling,and its no good for the u-joints.axles and rear ends.Use 4wd only when tracton is spotty or limited,so the tires will be able to slip often, releiving bindup pressure.
 

mike reeh

LawnSite Member
Location
san diego
ugh, it is VERY hard on the drivetrain when you make sharp turns on pavement in 4WD. I try as best I can to keep that from happening, ever. especially with the older trucks, its just asking for trouble.

you're right about the full-time 4wd np203.. it has a differential for normal driving but you're still in 4wd.. when its really bad you put it in lo-loc or hi-loc for full traction.

mike
 

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