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 Scary lock-up on motorway 
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Joined: Thu Dec 21, 2006 12:11 pm
Posts: 8
Location: Ireland
Post Scary lock-up on motorway
I was travelling on the motorway at 90 kmph in my Pinzgauer when suddenly the drive train seemed to lock up and I swerved into the fast lane missing a car by inches. Cars behind were also lucky to avoid an impact. It was scary! Thankfully, I managed to get her over to the hard shoulder.

At first she wouldn't budge, but after a bit of rocking, I found I could drive her in a straight line forwards or backwards, and was able to shift through all gears. I drove her off the motorway, but when I tried to turn on the exit ramp, I found I could barely steer her. I just drove her up on the grass verge and eventually got her towed.

Does anyone have any idea what happened? I had a look under the front and could see nothing obviously wrong. I didn't see anything broken or disconnected. What could it be? It was a hairy experience to say the least.


Mon Feb 12, 2018 10:14 am
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Joined: Wed Apr 14, 2004 9:58 pm
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Location: Idyllwild, CA
Post Re: Scary lock-up on motorway
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suddenly the drive train seemed to lock up and I swerved into the fast lane
Did the "lock up" make the truck swerve a lot, or just a bit?
Two scenarios come to mind: 1) the emergency brake was dragging enough to heat and engage more fully, creating the "lock up" condition. But since this is on the main drive shaft it should have affected both sides relatively equally, although locking the rear axle at speed will make the vehicle understeer (to put it mildly!). Or 2) One of the brake shoe's lining came loose and wedged up in that wheel; this will very obviously create a huge drag on only one side. At 90kph this would be expected to have horrendous effect if it happened on the front axle, less so if it happened on the rear axle.

If safe to do so, drive it around the block a few times at relatively low speeds (30-40 kph tops) and see if you notice heating of the parking brake area; this would point to #1. Pull the drums off all wheels and inspect the brake shoes, this will prove or disprove #2. Let us know what you find.

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Mon Feb 12, 2018 11:45 am
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Joined: Wed Feb 01, 2012 11:39 am
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Location: Ontario, Canada
Post Re: Scary lock-up on motorway
I would pull the drums off all wheels and inspect the brake shoes 1st before you do any more driving :)

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Mon Feb 12, 2018 12:01 pm
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Joined: Wed Jan 18, 2012 9:07 am
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Location: Vienna, Austria
Post Re: Scary lock-up on motorway
engaged front locker ???

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Mon Feb 12, 2018 1:19 pm
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Joined: Mon Apr 12, 2004 9:36 pm
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Location: Ca. or lost in South West USA
Post Re: Scary lock-up on motorway
What do you mean by "seemed to lock up" exactly? Did the tires lock and leave rubber on the road? Did the steering wheel violently turn itself?

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Mon Feb 12, 2018 2:11 pm
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Joined: Thu Dec 21, 2006 12:11 pm
Posts: 8
Location: Ireland
Post Re: Scary lock-up on motorway
Quote:
Two scenarios come to mind: 1) the emergency brake was dragging enough to heat and engage more fully, creating the "lock up" condition. But since this is on the main drive shaft it should have affected both sides relatively equally, although locking the rear axle at speed will make the vehicle understeer (to put it mildly!). Or 2) One of the brake shoe's lining came loose and wedged up in that wheel; this will very obviously create a huge drag on only one side. At 90kph this would be expected to have horrendous effect if it happened on the front axle, less so if it happened on the rear axle.


Thanks. The emergency brake and normal brakes were working fine afterwards, so not that. Maybe it wasn't clear in my post, but she drove fine after the incident, fine except I couldn't steer, so I'm starting to suspect the front diff.


Mon Feb 12, 2018 4:17 pm
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Joined: Thu Dec 21, 2006 12:11 pm
Posts: 8
Location: Ireland
Post Re: Scary lock-up on motorway
Hotzenplotz wrote:
engaged front locker ???


Maybe. Afterwards, it was driving fine but felt like the front diff lock was on.


Mon Feb 12, 2018 4:19 pm
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Joined: Thu Dec 21, 2006 12:11 pm
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Location: Ireland
Post Re: Scary lock-up on motorway
VinceAtReal4x4s wrote:
What do you mean by "seemed to lock up" exactly? Did the tires lock and leave rubber on the road? Did the steering wheel violently turn itself?

The steering wheel did turn itself violently. And the Pinz lunged forward. I didn't look for rubber on the road, but it wouldn't surprise me it I left some behind!


Mon Feb 12, 2018 4:28 pm
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Post Re: Scary lock-up on motorway
Your locker cant just engage on its own but even if so, you'd have to be turning to some degree for that to cause a driving issue. In a mostly straight line, you can't feel it at all. I engage lockers on the road often, when driving straight, to exercise them after non use for a while.

If not the above brake issues, something is either loose, broke or is about to break somewhere in the driveline (front diff?)... that's my guess.

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Mon Feb 12, 2018 5:11 pm
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Joined: Fri Apr 16, 2004 7:08 am
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Location: Blue Mounds, WI
Post Re: Scary lock-up on motorway
I once had a tranny go into 1st and 3rd as I shifted and it locked up the rear end (Econoline100 van). But this doesn't sound similar, since you can still drive it.
Bermo wrote:
when I tried to turn on the exit ramp, I found I could barely steer her.

To me, this suggests the front differential locker is an issue, same as others have suggested. But it seems like an unlikely way to fail.
I'd jack up both front tires and see if they both spin the same direction (diff. locked) or not.

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Mon Feb 12, 2018 6:46 pm
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Joined: Wed Apr 14, 2004 9:58 pm
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Location: Idyllwild, CA
Post Re: Scary lock-up on motorway
Quote:
To me, this suggests the front differential locker is an issue, same as others have suggested. But it seems like an unlikely way to fail.
Unless the diff "just failed" due to insufficient lubrication. Have you checked the fluid levels in the diffs? If they are low, drain them and inspect the diff bevel gears through the drain hole (let them drain for a long time so you can get under them with a light and look inside). Lift one wheel of each axle, have someone rotate that wheel while you are looking up the drain hole. Search for "execution II" to learn what should be expected to be seen for execution I and II, what the difference is, and why they created execution II. If you don't know what you are seeing, check out https://www.youtube.com/watch?v=G9wNbXZf6wU to learn how they work and best see what is in there.

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Mon Feb 12, 2018 7:37 pm
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Joined: Thu Dec 21, 2006 12:11 pm
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Post Re: Scary lock-up on motorway
I jacked up the front axle and rotated one wheel and the other rotates with it, they are locked together. I activated the front diff lock and there was no change. I took it off again and still no change, the two wheels are locked together in rotation. The steering was fine, I did a full lock in both directions and the wheel could rotate, but in lock. So there is definitely a problem there. As a matter of interest, I jacked up the rear and that was fine, the wheels can rotate independently and rotated together when the rear lock was activated. I put the four wheel lock on and that worked as well. So the front diff if locked with the diff lock lever in the up position. So, I suppose I should investigate the front diff lock activation?


Sat Feb 17, 2018 10:47 am
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Joined: Wed Apr 14, 2004 9:58 pm
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Location: Idyllwild, CA
Post Re: Scary lock-up on motorway
The front diff lock mechanism is much, much easier to check than a failed diff! But it won't hurt to drain the front diff and look for metal pieces, too; that is also not difficult. One or the other should tell you what happened.

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Sat Feb 17, 2018 10:55 am
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Joined: Thu Oct 06, 2011 4:25 pm
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Location: Mount Vernon WA USA
Post Re: Scary lock-up on motorway
The diff lock coming on would not cause the symptoms you described of it locking up on the motorway. I suspect there is something more going on such as failed bearings. Draining the diff is the first step.

Hopefully its something like the spider gears locked up. Still requires pulling the front diff assembly.


Sat Feb 17, 2018 1:11 pm
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