So were about to get a 10" snowstorm... the hose to my diaphragm is solid and whole... the vacuum switch was changed about a year ago, maybe 2 years ago... the hoses are all solid... the boot that goes on the diaphragm looked old and dried out, i clamped it with a ziptie and hoped that would be ok, but im not getting the "clunk"... i can hear the selector in the transfer case, but thats it... i havent used in 2 years due to a broken vacuum hose... the last time i tried to use it, it did that grinding thing where the shift fork doesnt stay locked in... if i put it in 4hi, the light stays solid, if i put to 4lo the light just flashes

 

I read somewhere that i could ziptie the diaphragm and that would activate the shift fork... idk if theres any truth to it... i might give it a shot here in a few minutes... its just now starting to snow... idk about u guys, but even with these 34s, if i dont have 4wd ****s useless... granted my k02s have seen better days 🙄🤷‍♂️

 

From your description the first place I'd check is the vacuum diaphragm under the battery tray.

I believe the best way to test this is remove the battery, and then reconnect it to the truck with battery cables (being careful to insulate them from one another). Then jack up the driver side front tire. Start the truck and put it in 4wd, keeping it in park. If the tire spins freely by hand, then pull the cable at the 4wd vacuum diaphragm with some vice grips, and have an assistant try spinning the wheel by hand. If the tire won't spin, then the diff locking collar is engaging, and you know that it's the diaphragm that is at least part of the problem.

This will isolate to see if the source of the problem is that vacuum diaphragm. Good luck, and please post back your results. If you need more help, we'll do our best. There's lots of people on here with a lot of knowledge who like to share.

 

ive owned this truck for 4 years now, and this forum has helped me repair so much stuff... old posts, **** from 2007 etc... when i did the seals on the transfer case, an old post on how to do it from this forum... i had a whole bunch of issues with my ignition a while back, this was my go to... right now im faced with a p0452 that ive had the whole time i owned the truck... re-ran all the evap hoses, 2 different fuel pumps (broke the first evap fitting &#129313 new filler neck, obviously new solenoids... couldnt for the life of me find the appropriate fuel tank gasket... the o-rings they send with it are trash and the lock ring wont seat... the L085 is also too fat, however, is the appropriate gasket... i busted out the old roll lock and sanded it down a little bit (obviously as flat as i could) and i finally got it to go... the harness for the evap sensor pulled out when i dropped the tank... so i got a new harness from autozone and thought 'perfect, i needed it to be a little longer anyway 🤷‍♂️' .... 😐 wired it up wrong 🤡 the signal is right... its the center... but the 5v and the low ref are crossed... after all that, i have to drop the tank again and swap those 2 wires... as soon as i reset, p0452 🤡 and now its, you know, 10 degrees and a blizzard... ill ride it like this until i can get in there again...

 

The 4wd thing tho, after i get home from physical therapy im gonna lift the battery up and try the zip tie and the diaphragm... ill ride with it fully engaged for this little snow storm were about to get, thats not the end of the world... as long as the shift fork engages and i can use it for now... the diaphragms only 50 bucks, but its Christmas 🎄

 

Off topic also, but i got a p0418 secondary air pump code... i put a new pump and rewired the whole little fuse cluster with fresh wiring that wasnt all green and corroded... i got power at the 30amp big fuse, nothing on the 10amp, and the motor dont even try to turn on... ill stop... im gonna have to post in the appropriate section for that, but... 🤬 thats ones got me bad... the p0452 i can nail down, that other one tho... i havent passed emissions in like 3 years and i cant renew my regi

 

If you have a little hand vacuum pump, try connecting it to the hose that goes to the actuator and applying vacuum. If it engages, the problem is somewhere in the switching and, as a temporary workaround, you might try connecting that hose directly to manifold vacuum so it's engaged any time the engine is running.

 

Thats a good idea... i have a mightyvac thing...

 

What year is your truck and, based off your description, would I be correct in assuming you have a 3-Button selector switch for the transfer case?

 

​​​​​​​its a 2001... yes its the 3 button... yesterday while i was trying to play around with the diaphragm i found the problem... the cable from the diaphragm to the differential is rusted... i squeezed it by hand and nothing happened... the diaphragm feels fine, but when i squeeze it theres no travel in the cable... i tried to retract it with the ole channel locks... no such luck...