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Runaway Truck


Flying Finn
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We are currently in North Georgia getting ready to head toward Orlando/Tampa......or so I thought.  Warmed up the truck (2001 770 with an Eaton auto-shift) and put the truck in reverse, feathering the clutch to gently back toward the trailer.   All the sudden the truck fully engages in reverse (I barely released the clutch).  I mashed  clutch pedal to the floor....still going.....hit the brake still moving then finally had to turn off the engine to get it stopped.   After I collected myself pulled well ahead thinking  maybe my foot wasn't on the clutch correctly.  Same thing happened.  Clutch went to the floor, truck still going in reverse had to  shut off the engine to get stopped.

No error codes or service lights went off.  Any ideas on what the heck may have happened???

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Since you have a 2001, I'm gonna say it's likely you have the same three pedal system as we.  In that case, you have a clutch issue, not a tranny problem.  As Darryl said, check the fluid level in your clutch reservoir.  It's on the engine side of the firewall, outside the steering column.

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What Mark and Rickeieio said - We have the same truck w/ 3 pedal & autoshift ....Installing a new (different) reservoir & slave is pretty easy, Bleeding it is a pain is the A$$. And despite what it looks like, don't try to adjust the linkage, per the manufacturer.

PM me if you need more info.

Paul

 

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I once had an 18speed manual do pretty much the same thing, stepped on the clutch, put into gear like normal and took off. Next time I stepped on the clutch it worked normally as I stepped on it but as I was letting it up all of the sudden the pedal dropped to the floor and the truck stalled from rapid clutch engagement in a high starting gear. Upon disassembly/diagnosis they found that the clutch was pretty much worn out but the main cause was the throwout bearing had come apart.

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  • 2 weeks later...

Wanted to follow up and let you guys know what was wrong.  The clutch master cylinder failed and the clutch slave cylinder was close behind.  Also had a hydraulic line that was cracked but not yet leaking.  Took the tuck to Vanguard in Adairsville, GA for the repair.  Cost for the repair was $1,300.00. They replaced both cylinders, hydraulic line, refreshed the hydraulic fluid, test drove.

So far so good.  Never saw that one coming.  If you have a Gen 2 auto-shift may want to have the clutch hydraulics looked at.

Could save you a catastrophic failure like I had.

Brad

 

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  • 2 weeks later...
  • 2 weeks later...
48 minutes ago, Padraic said:

Do all Volvo truck has a clutch master cylinder?  My truck is a 98 Volvo 610, does it have a clutch master cylinder and hydraulic lines?

Yes, if you have a 10 speed you have a master cylinder.  Open the hood, and look next to the windshield washer reservoir.  There should be a reservoir there that has fluid in it. That's the master,  Follow the tube out of the bottom down to the next object attached to the line, that's the slave is located down on the transmission housing.

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On 2/3/2018 at 11:09 PM, Alie&Jim's Carrilite said:

Yes, if you have a 10 speed you have a master cylinder.  Open the hood, and look next to the windshield washer reservoir.  There should be a reservoir there that has fluid in it. That's the master,  Follow the tube out of the bottom down to the next object attached to the line, that's the slave is located down on the transmission housing.

Thanks, Alie & Jim. Nice to know, I have a ten speed 1 to 5 and flip the switch for 6 to 10. that is something I don't know what I don't know. Time to dig into the detail. 

Below is a picture, is that it? It said on the cap, use brake fluid only.

Clutch hydraulic-1.jpg

Edited by Padraic
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on a old school commercial rig fully loaded.

throttle return spring broke. truck sped up to 80mph right now.

that is fun. 

turn off motor at that speed. sure pre computers. but every thing still went dead. but at lest got it stopped before something else took place. not on a lonely streach of rd.  but in a majer city aera during the day.

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Yesterday, I too had a run away truck.  Cruising up TX 118 south of Alpine, touch the brakes going into a curve and the cruise control doesn't shut off.  Play with the stalk and finally get it to relinquish control of the ship.

I grew up around some pretty good mechanics, and one lesson that was beat into my noggin was, whenever you have a sudden problem, look where you last worked on a related system.  Well, during our stay in Terlingua, I removed all traces of two brake controllers. Dug around behind the instruments and sure enough, the plug was out of the brake light switch.  I hadn't removed it, but it must not have been securely snapped in place by the last person who had it out.

There's no end to the things that can go wrong at inconvenient times.

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  • 2 weeks later...
On 2/8/2018 at 6:18 PM, Alie&Jim's Carrilite said:

That's it.  I flushed mine and refilled with fresh fluid.  Made a huge difference in how hard the clutch was to push.  You do have to do this from the bottom though, otherwise you'll trap air in it.

That is good to know, I get tired on my left leg often.

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