99 tahoe grinding transfer case at low acceleration

[e_bennett]

I have a 99 Tahoe that started making a grinding noise when I start accelerating while in 2H. It is not coming from the transmission and sounds like it is in the 4WD transfer case. I can put the truck in 4Lo and 4Hi (although the 4 HI light doesn't actually come on but feels like its in 4H). In both of these there is no grinding when starting to accelerate or driving. When I am back in 2H (my indicator light says I am in 2H), i get the grinding noise again at low acceleration. Once I get going above 20mph or so or if I let off the gas when I hear it, the grinding will go away Almost sounds like the 4WD transfer case gears are sitting too close and when I accelerate in 2H, there is a little bit of play that cause the gears to come in contact slightly. Not sure if this is the case but sure sounds like it. Any thoughts on this? I just dropped $1700 into this truck for another issue and need to fix this on a budget. Thanks in advance for any info.

 

[Rd05lly]

What does fuild look like in T case?

 

[areaandrew]

I cant remember how the tahoes of that year were, but if its servo ativated front dif. Then i know excatly what the problem is. If its electric then i wouldnt know. Could you tell me if your front diff is servo or electric?

 

[e_bennett]

I think its servo. Gas charged, electrically heated expands gas? Could that servo just not be pulling all the way back out when not engaged? thats kind of what I was thinking after posting this message.

 

[areaandrew]

If it is servo, then its mosrlt likely vacum activated, if thats the case then there is a vaccumm switch on top of the transfer case driver side, $17 at napa. What happens is that switch gets stuck half way and causes a slight vacum pull on that servo causing the actuator gear to partically engauage. Switching to 4x4 makes it stop. Another sign of that being the problem is an oily sunstance blowing out of your defroster and or t-case fluid in the cigaret lighter holder. Sane thing was happening on my s10 and it took me 2 years of playing with it to determine the problem, by that time i had shredded a gear in my front dif, wasnt too hard of a fix tho. Hope this helps!

 

[lesterl]

Jack the front end up, rotate one tire, do you hear the noise, does the other wheel try to spin?

 

[WisYukon]

My 98 is making a tink tink tink sound at low speed from the front. Is that the sound your hearing? I wouldn't call this a grinding noise but it sounds axle/diff related. It doesn't always do it either.