Hessitation/Stuttering/Grabbing I NEED HELP!!!

[bornchevy]

Well since I got my suburban engine running decent I have been taking it back and forth to work and there I fount my new problem. I'm new to the IFS 4x4 setup so I have no experience with the front differential. While I'm driving after about 10 minuets or so every few minuets it feel like the front end is trying to engage but its only momentary. I honestly have no idea what it could be or where to post this. It grabs and stutters for a second then its fine, then a few minuets later it dose it again. This is also the push button auto 4x4 system. This is above my head, I have no idea what is going on and I'm completely confused. It doesn't seem like it could be an engine problem, could it be the trans or transfer case? Please help, if you have any questions or need more information, or pictures if needed let me know and I will tell you the best I can. I am not new to the gmt400 but its my first IFS 4x4.

1999 suburban k1500 350, 4l60e, auto 4x4


My last 2 trucks were a 88 Scottsdale eclb 350, and a 98 cclb dually 454. Never had this problem with those trucks so that's why I think this might be a 4x4 problem.

 

[bornchevy]

If anybody has any suggestions of what it could be or any advice I would appreciate it.

 

[twomanymontes]

Kind of sounds like the Encoder motor on the transfer case is stuck between positions. When you change the 4WD positions, does the button lights flash? There might be a code stored in the transfercase module.

 

[twomanymontes]

Come to think of it, The Actuator on the front axle might be bound up and not releasing completely as well.

 

[bornchevy]

how would you check the transfer case module? and the actuator in the front axle how would you check that? This weekend I will be tearing some stuff out to check it and would like to get to the items you suggested while I'm there. Thank you for your advise.

 

[bornchevy]

I was just under the suburban and i had my gf put it in 4Hi and 4Lo and when putting it in 4Lo it makes a thud and a clank, also the transfer case sounds like its forcing itself into 4Hi almost like its not smoothly going into 4Hi. (compared to my dads 06 2500 which doesn't make any noise going into 4 hi or 4lo) I also noticed that the yoke on the rear of the transfer case has a lot of play up down and side to side when wiggling it around and some rotational play. Not sure about that play back there but if someone could let me know if that's normal.

twomanymontes
when i put it in 4x anything the light blinks for a few seconds then clanks into the selected drive.

 

[twomanymontes]

The light blinking and then the clunk into position is normal. Your dad had a much newer truck and they have a different set up so no noise. The rotational play in the shaft is just the slop of the transfer case chain/gears and the rear end gears. that's pretty much normal to a point. The up and down play of the yoke should be minimal at best, if it's clunking a lot, then the rear bushing is worn.

Sounds like your encoder motor is working so that's good.

The actuator on the front axle screws into the housing on the passenger side. Try to remove it and then drive the truck, if it doesn't have the issue, then replace the actuator. Pretty common failure. Mostly because the wires rot off, But ocaisionallly they get stuck between travel positions.

Hope this helps

 

[bornchevy]

Thank you, you have been very helpful. I'll try the removal and see what happens. on the way home today it did it again going up a slight grade. it shuddered about 13-14 times within 2 minuets. about 1500 rpm, no rpm drop. about 40 mph. which is different from when it was doing.