rattle in 2wd

[Dane]

You can get other leaks in that whole line. I replaced my entire vacuum line because I was sick of tracing leaks. It's like $30 and takes about 15 minutes in your garage with only a screwdriver or something to pry the little plastic plugs out.
A vacuum gauge is extremely helpful for troubleshooting the system and finding leaks. I use the one that came with my harbor freight brake bleeding kit. I think it was something like $15.

 

[USCxGAMECOCK]

One thing you can look at is the check valve for the vacuum line. You can disconnect one side of the hose and suck and blow into the check valve. You shouldn't be able to both blow air and suck air freely. I was able to determine that with that caveman type method. Replaced that little valve and bingo, it was all good.

 

[wipit]

Thanks

 

[Jr24]

My 2018 started doing the same thing back in December. It would only do it periodically for a few seconds under light throttle. On the first trip to the dealer, I got the “could not duplicate” response. On the second trip, I left the truck overnight and they put 40 miles on it and still couldn’t duplicate the noise even though at this point, I had caught the noise on video and showed them the video. I told them I thought it was an IWE problem and they admitted they thought it was an IWE problem, but needed to hear it doing it. After much discussion, they finally brought their tech who specializes in front end and 4WD problems to talk to me. In about 30 seconds, he described the exact circumstances of when it would do it and said he wanted to try replacing the check valve for me to try which took him all of about 2 minutes to do. 2000 miles later and several 4WD engagements later, I have yet to hear another noise or have any problem at all. Here’s a pic of the new part complete with part number label.