another 4wd issue but with a new spin...4wd was out and i was having issues with both the vacuum and the actuator/motor itself. i replaced the motor and vacuum lines and that fixed the problem, for about a day.

now the truck is going into 4wd (light on and front wheels pulling through the snow) but there is now a noise and vibration from the front of the truck. it sounds like a loud clicking/popping sound (i suck at describing sounds) and feels like the collar in the cad is slipping on the axle shaft. when shifting back into 2hi the collar/actuator is hanging up and i have to put the truck in reverse to release the tension on the collar - as soon as back up ever so slightly it shifts right back into 2hi.

i took the cad apart again immediately (fortunately was only a block from home when this happened)...the intermediate axle shaft is in good condition but could feel some ever-so-slightly gnarled edges from the collar "slippage"....but with that said, the collar still slides very easily by hand over the int axle shaft, didn't seem to be hanging up on anything....my conclusion is it feels like the collar is simply not seating far enough over the int shaft and slipping off when in 4wd but not sure how to confirm this or fix it

i had a worn u joint on front passenger wheel that needed replacing, so i did that to make sure it wasn't the cause of the noise/issue....i wasn't

i am somewhat lost at this point....i am kicking myself for not just going with the posi-lok in the first place, but not sure that will fix my problem at this point anyway....the money pisses me off, but that aside i just want to get this thing running and want to avoid taking it to a mechanic (i should be able to fix this)

thanks in advance for help and thoughts about wtf is going

db

 

Yeah, it sounds like it isn't moving all the way. That could be bad vacuum. Trace the vacuum lines all the way back and check for a leak. Other than that it might be an adjustment. I have the Posi-Lok now and it can be adjusted. Has to be adjusted. I can't remember now on the stock setup but it too might need to be adjusted. Since it isn't shifting all the way do not run it in 4 at all. You'll tear it up bad. You have to pull the axle apart to replace the colar and that is a heck of a lot more work.

 

Check the splines on the collar for any little burs that might be allowing it to hang up and not slide over all the way.

 

there are very slight burs/gnarls on the end of the mid axle shaft, but not on the collar....with the cad off, the collar slides over the mid axle shaft very easily, no hanging up at all when it's lined up

 

to take it a step further....i pulled the cad off today and got out the measuring tape...with the truck in 4hi, i shut it down and carefully removed the cad and measured (of course this is not super precise), but it appears that the collar is in fact sitting almost evenly over the mid axle and outter axle shaft...

argh, not sure where to go next

 

can you put the truck up on 4 jack stands and have an assistant operate brakes/shifter while you observe whats popping.

its somewhat normal for the collar to be sluggish to engage/disengage. wear in the axle bushings can create some movement and misalignment, plus drive line tension, etc. i used to have to back up, pull forward to get mine to move. with posilok, mine is still sometimes sticky, but with button in hand i can see whether its engaged or not.

in your test - i understand that you shifted to 4wd, drove it a little. experienced the popping. then disassembled it to see if the collar was misaligned. but it was not. so my first guess is that the popping is coming from the front drive shaft. hows it look/feel.

 

i put it up on stands and it does not appear to be making the popping when the truck is not under load. it honestly feels like a u-joint but the bad u-joint has been replaced and the other is in good working order.

the popping is much more pronounced when the wheel is turned however it is still evident even when driving straight. i have inspected the splines inside the collar and they are in great shape, and the gnarled edges on the mid axle shaft are not alarming and i attribute them to normal wear of the collar engaging. i talked to a buddy that is a mechanic and he swung by last night as he was thinking it might be a spider gear....after a short ride he agreed that it felt/sounded like a u-joint, but his inspection confirmed the other u-joint is fine

perhaps that most frustrating part about this is that i can't figure it out and it's looking like i am going to have to take into the shop....i hate admitting defeat and taking it to a shop....knowing my luck, i will get this figured out and fixed once all the snow is gone and i don't need 4wd

 

did you check your front drive shaft u-joints ? (in addition to front axle u-joints).



edit - here's another interesting test i just thought off.
label your vac lines at the cad so you know how they are supposed to go.
you have vac on one in 2wd and vac on the other in 4wd. this change in vac causes the vac diaphram to move from one side to the other, which causes the collar to move.
the t-case shift lever causes that vac to change back and forth.

now swap the vac lines at the cad.
this causes the axle to couple up in 2wd. meanwhile the front drive shaft is not turning. it won't hurt anything other than slightly increased drag and slightly decreased mpg.
drive it around some and see if it still pops.
if it pops, then its in the axle, and not the drive shaft.
if it doesn't pop, then its in the drive shaft.

 

interesting idea on reversing the vac lines...will give it a shot this weekend to see what i come up with...will be checking the drive shaft u joint and digging into the front diff this weekend

thanks dhv

 

to close the loop on this one, truck is now fixed. replaced 3 u joints on drive shaft to front axle along with u joint ball and spring for the centering yoke....the drive shaft was apparently pretty badly out of alignment, which is now corrected as well