1999 silverado 4x4 wont engage

warthog87 · June 29, 2015

hey my name is ryan. new to the site but I like what I see. I have a 1999 Silverado 1500 and the 4x4 wont engage. the actuator seems to be trying to engage but the front wheels don't spin. all the lights on the dash seem to be working. I am lost is I am to the point of buying a new front diff. if anyone can help me with this I would really appreciate saving some money.

gmtech4 · June 30, 2015

hey my name is ryan. new to the site but I like what I see. I have a 1999 Silverado 1500 and the 4x4 wont engage. the actuator seems to be trying to engage but the front wheels don't spin. all the lights on the dash seem to be working. I am lost is I am to the point of buying a new front diff. if anyone can help me with this I would really appreciate saving some money.

Lol, don't jump to a diff there bud , lol

Tires off the ground when checking ?

Codes stored in TCCM ?

If little tech skills , best to get a buddy who is or shop time

warthog87 · June 30, 2015

I had both tires off the ground. the truck is in park and in 4hi. I can spin the tires but only one at a time. I was told one should spin the opposite direction. when it is in 4hi I cant spin the front drive shaft. but when in 2wd I can. and not sure what TCCM is? my buddy said it could be my spider gears? another told me it could be the front axel. also I am having trouble figuring out how to figure out what gear it is no sticker on the diff

warthog87 · June 30, 2015

Trying to look up RPO codes can't figure it out

CapitalTruck · July 1, 2015

I'm not entirely convinced that you have a problem...it isn't easy to spin the front wheels. All of your descriptions point to a functional system.

gmtech4 · July 1, 2015

See post # 2 !!!!!!!!!

You'd know it if the diff was junk by the sudden stop while driving and oil on the ground ,

Do not continue in the thought process you're going

STOP !!!!

grampadirt · July 1, 2015

I had both tires off the ground. the truck is in park and in 4hi. I can spin the tires but only one at a time. I was told one should spin the opposite direction. when it is in 4hi I cant spin the front drive shaft. but when in 2wd I can. and not sure what TCCM is? my buddy said it could be my spider gears? another told me it could be the front axel. also I am having trouble figuring out how to figure out what gear it is no sticker on the diff

Find a shop that will let you put it on a lift getting all four wheels off the ground(like Rob says),put the trans in Neutral & the transfer case in 4hi or 4lo and try all that again.When either 4hi or 4lo is engaged and the truck is on the ground you should not be able to spin the front drive shaft.

What happened that leads you to believe the front axle isn't engaging?

You do know that a stock 4x4 GM(I believe all mfgrs are this way as well)truck will never have both wheels locked in together,right?

warthog87 · July 1, 2015

I will try this today. the only reason I thought it is not engaging is because I was told when I spin one wheel the opposite side should spin the opposite way