Long time member, rarely post unless I need help, and I need some. This is going to be lengthy, but it will hopefully paint a good enough picture.

Truck is a 2007 KR 4x4, 3.73 gears and limited slip in the rear. Has 98500 miles.

Ok, so, for some time I have had a grinding in the front end when in overdrive while under slight acceleration. It would come and go, but just recently got worse. Also, just recently, when in 4X4 hi, it will "grind" while decelerating and it takes a LONG time to disengage from 4x4hi. By long, I mean, 15 seconds while driving, at least. Spoke with the dealer (good, trusted friends) and they mentioned the IWE's and solenoid switch for the 4x4 system.

I purchased 2 new Dorman IWE's and went to trouble shooting everything. I also purchased the necessary oil to change the front differential, rear differential and transfer case (tranny was done 20K miles ago).

Here is what I found:
- With the old IWE's everything held vacuum.
- Replaced solenoid switch just to be sure.
- Found bad vacuum check valve near solenoid switch, replaced.
- Found cracked line right near bad check valve, replaced.
- Right IWE, spring was broken, not maintaining a seal and the teeth showed grinding. Replaced with the new Dorman IWE.
- Left IWE, bad shape. Plastic ring was cracked, showed grinding. Replaced with Dorman IWE.
- Transfer case fluid wasn't bad, but wasn't great. Replaced with Mercon V.
- Front differential, oil was horrible. Water got in system and oil came out a milky light brown. "flushed" all inside gears with oil, cleaned everything. Teeth and all looked ok. No pitting, no problems seen. Filled with fresh oil.

Now, I thought this would all correct the problems.... only problem it corrected was the grinding while in overdrive. The truck still "grinds" when decelerating in 4x4 hi. You can only hear it while at speeds of 25mph and up. While accelerating (hi or normal or light), there is no grinding. But when you let your foot off the gas, 4 seconds (I counted) later, the grinding noise starts. I "tested" the 4x4 (went to an open dirt lot) and found that all tires are throwing dirt and getting power.

Anyone have any ideas? The hubs and bearings all looked fine. The only thing I can think of is I am having a vacuum issue somehow when the truck is not under a load.

Any help would be great.

Thanks

Andy

 

Sounds like you went through just about everything I would have recommended already. Just out of curiosity, do you have a manual Transfer Case shift lever or the Electronic Shift on the Fly (ESOF) switch on the dash? The reason I ask is that I'm wondering if your Transfer Case is fully engaged or not.

 

Just had another thought. You said at least one of your old IWEs was pretty well torn up. That's pretty normal when you have the other issues you noted. A partially engaged IWE tears things up pretty well. On that note, what did the splines on your axle shafts look like? I'm almost wondering if some of them got torn up and your new IWEs are not fully engaging / disengaging.

 

I have the ESOF. the splines and everything looked and felt great. I took pictures and showed them to my guys at the dealership and they agreed, but they didn't actually touch and inspect them.

Does anyone know how the vacuum reservoir works? If it were going bad or had a leak, would it do the same thing?

I am going to pull all other lines tomorrow and inspect / replace them and re-inspect the other check valves.

Any other ideas?

 

Did a little testing this morning, wanted to pass it along incase it triggers an idea from anyone.

I put the truck into 4x4 hi and it engaged fine. As I accelerated, everything sounded fine. I let off the gas and again, there was the grinding noise after a few seconds. Now, if I get on the gas while in 4x4 and in gear, the noise will go away. This time, I put the truck in neutral and gave it a little throttle, and the noise stayed.

Any ideas?

 

Were you rolling when you put it in Neutral or at a dead stop?

 

I was going down the road at around 30-35 mph.

I did some more testing today. I unplugged the vacuum lines which engaged the IWE. I plugged up the vacuum line and went for a short ride. During this time, with the switch in 4X2, no noise was heard, even though the IWE were engaged as there was no vacuum to keep them unlocked. Now, when I turned the switch to 4x4, the noise came back when I would let off the gas.

I am beginning to wonder if it isn't my transfer case. I am going to get under the truck this weekend (too cold and snowy right now) while its on the lift and let the drive line move so I can try and hear where it is coming from. Anyone have a thought at what else to do?

I believe I have the BW4406 transfer case. Ho bad are these to work on?

Thanks

Andy

 

That does sound like a transfer case issue now.