4wd noise

[boltnnuts]

i have a 02 chevy silverado 2500hd ext cab with 4wd.when i push the button to engage 4wd a grinding noise comes from the front axle.fluid level ok.internal damage maybe?if so what is it and how hard .thanks

[j cAT]

Originally Posted by boltnnuts

i have a 02 chevy silverado 2500hd ext cab with 4wd.when i push the button to engage 4wd a grinding noise comes from the front axle.fluid level ok.internal damage maybe?if so what is it and how hard .thanks

what happens when you place in the auto 4wd position ?
what color is the front diff oil ? what color is the transfercase fluid ? how often do you replace these fluids ?? do you drive on solid, dry pavement in any 4wd position often ?

[boltnnuts]

dont have auto 4wd.change fluids once a yr.only time i use 4wd is when its snowing alot or on job site where mud or snow is a problem.not sure of color thanks

[j cAT]

Originally Posted by boltnnuts

dont have auto 4wd.change fluids once a yr.only time i use 4wd is when its snowing alot or on job site where mud or snow is a problem.not sure of color thanks

the front diff uses 80-90wt gear oil, should be yellow..the transfercase fluid is tracII this should be a blue/purple color..

do "YOU" ,,,do this once a year, change of fluids ? if not It is possible the wrong fluids were used..check for color contamination..

[boltnnuts]

yeah i change it regulary .yes the correct fluids r in it.i thought u ment what color when drained.sounds like metal on metal.i should go check 4 metal shavings in the oil.

[j cAT]

Originally Posted by boltnnuts

yeah i change it regulary .yes the correct fluids r in it.i thought u ment what color when drained.sounds like metal on metal.i should go check 4 metal shavings in the oil.

metal shavings ! how big ? what componet..?

as far as color goes usually the front diff turns gray ,,,the transfercase black..when things start failing..with you fliud change intervals, it should be perfect...

[wagslick]

The same symptoms showed up today on my truck (99 silver z71). I throw it in 4wd, wait for a moment then begin to accelerate. The back tires spin but front does nothing. The light says it's in 4wd but it's clearly not. Also, if I slowly accelerate I hear a mild clunk (not the typical clunk from the back these trucks are famous for). It's a clunk I'm almost certain is from the front differential. No codes or lights to signal any 4wd error. Any ideas?

[j cAT]

Originally Posted by wagslick

The same symptoms showed up today on my truck (99 silver z71). I throw it in 4wd, wait for a moment then begin to accelerate. The back tires spin but front does nothing. The light says it's in 4wd but it's clearly not. Also, if I slowly accelerate I hear a mild clunk (not the typical clunk from the back these trucks are famous for). It's a clunk I'm almost certain is from the front differential. No codes or lights to signal any 4wd error. Any ideas?

this would indicate the encoder transfercase motor is not engaging the front axles to the rear axles...that is what it does..

the front diff actuator motor only locks the front axles together as one..

does nothing with your issue of front wheels not engaged with the rear.

remove encoder motor and check for operation ..check wires connections to this motor..fluid condition/holes in the transfercase body etc..

[wagslick]

Excellent Jcat! I'll check it out. I appreciate the help.

[Silverado6x6]

Replacing the encoder motor isn't too hard, you have to remove the front propeller shaft and carefully unplug the wire harness, after that its three long bolts using a 15mm socket size, they will have some light thread locking compound on them. When you go to install it eyeball the spline to see if it matched the drive end on the encoder or you won't engage it properly, turn the one on the transfer case to get it in the right position, this is in case something was moved through testing or checking, make sure the seal plate and O ring is still intact. If you don't have the "mini" skid plate I suggest either getting one or make your own, a home made one will be better.

The front motor might possibly have some water/oil sludge in it and when it gets cold could freeze, I say that because of the last front diff I changed the fluid on it was a 2001 2500HD and it did have some water in the fluid, check the vent to see if its still intact.

[wagslick]

Originally Posted by j cAT

this would indicate the encoder transfercase motor is not engaging the front axles to the rear axles...that is what it does..

the front diff actuator motor only locks the front axles together as one..

does nothing with your issue of front wheels not engaged with the rear.

remove encoder motor and check for operation ..check wires connections to this motor..fluid condition/holes in the transfercase body etc..

Is the encoder transfercase motor also known as the tansfer case shift motor?