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Posi-Lock problems...

2K views 8 replies 6 participants last post by  SpedJeep 
#1 ·
Bought a Posi-Lock kit for my YJ, intended to install it myself, and my back went out. Screws on the vacuum-motor case were rusted in, too. I'm not that keen on extracting stubborn bolts...I took it to a local shop. I'd done some minor trade before and apparently they're self-styled Jeep experts; there's always a Wrangler or a CJ in their shop. Been around five years at least, and the owner's an old guy...

That's all to the good. I gave him the Posi-Lock kit and he gave it to his underling, a not-that-bright kid of unknown talents (he does much of the shopwork). Got it back as promised..

Slick job, nice and neat. Only trouble is, when the front axle is engaged at 40+ mph, I have vibration all throughout the Jeep. A buzzing, not a shaking...the bare-metal floors amplify it. It's the front axle; I hear it if the transfer case is engaged or not. If I engage the transfer case with the front axle unlocked, no vibration from the driveline.

Anyone have any ideas?
 
#2 ·
Front ujoints possibly? Maybe look into getting your front driveshaft balanced, or it could possibly be bent.
 
#4 ·
Try going 40 to make it vibrate. Then, slowly disengage the posi to unlock the right front tire. (don't worry it will work). Does the vibration stop? If so, I can only imagine that the kid somehow messed up the installation. If it does not stop, it is something else.
 
#6 ·
paultyler said:
Try going 40 to make it vibrate. Then, slowly disengage the posi to unlock the right front tire. (don't worry it will work). Does the vibration stop? If so, I can only imagine that the kid somehow messed up the installation. If it does not stop, it is something else.
That's another problem, and also part of the difficulty in diagnosis. The Posi-Lock binds up at speed...I have to reduce to walking speed to disengage. That's with the transfer case engaged or disengaged...makes no difference.

With the transfer case engaged there is no vibration. With the driveline spinning but not locked up at the axle, no vibes.

With the axle engaged, there's vibration. Engaged or disengaged.

Just before I had the shop install the Posi-Lock I changed all fluids, including tranny and transfer and front diff. The u-joints are tight; I've inspected them and greased them.
 
#7 ·
sounds like the kid installed the fork backwards and it's not fully engaging the inner shaft because backwards it's not pulling the collar over far enough. just far enough to grind against the splines causing the buzzing vibe instead of a shake. either that or the fork is worn out doing the same thing or the cable isn't adjusted properly. those would be my guesses
 
#8 ·
sentinal02 said:
sounds like the kid installed the fork backwards and it's not fully engaging the inner shaft because backwards it's not pulling the collar over far enough. just far enough to grind against the splines causing the buzzing vibe instead of a shake. either that or the fork is worn out doing the same thing or the cable isn't adjusted properly. those would be my guesses
That's helpful.

The fork is new. We, the old guy and I, had a long discussion about that. The installation instructions recommended a replacement for the aluminum fork; and the old-timer seconded it. Paid shop rates for a cast-iron replacement.

Use? It has two stops; the first is an incomplete engagement. (Gears not meshed.) I have to roll the unit to slide the engagement into lock.

Fork backward? I didn't have a look at the part. Is that a common mistake?

Engagement is positive. I have checked...the usual tests, try to turn the driveshaft, a slow roll in a circle in 4wd...it's not chipping the gears.
 
#9 ·
In the directions is mentions low speeds to engage and disengage the posi lok. The fork ( and collar) that engages the axles is probably just barley engage and is causing the vibration. I know sometimes (for me) if it's not fully engaged it will make a shaking metally sound. That little 1/4 of and inche really makes a differecne. May also need to be adjusted...not sure but I think if thats the case the whole housing has to come out and adjust the jam nut again. Take a look at the directions or call the company if nothing else. It's a pretty cool little mod when it works right. :thumbsup:

Good luck
 
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