Unselor Posted April 7, 2014 Share Posted April 7, 2014 Guys, I need some input. Last Friday, on a haul from Memphis to The Gulf Coast the truck would be pulling good up a hill and the engine would just rev up on it's own. If you got out of the throttle, the engine would slow back to normal RPM and you could accelerate again and it would be fine. It did this 4 times that night. On Monday, after sitting for the weekend, it started doing it in 6th gear and 9th gear too. The load was light, around 15,000#. It hasn't ever done this before, even fully loaded in steeper hills. There aren't alot of steep hills between Memphis and South Mississippi to begin with. 2007 CH613. trans is a T310, engine is ASET 427 and it stayed in high gear the entire trip on Friday. Would a clutch that's on it's way out cause this? It feels good, has a good pedal and seems to have the correct free travel after it engages. Someone mentioned the range selector could be kicking out of high. Is there a "neutral" position that it could go into and make the engine rev until you ease off the throttle and make it engage again? Any help would be greatly appreciated. Quote Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/ Share on other sites More sharing options...
theakerstwo Posted April 7, 2014 Share Posted April 7, 2014 Sounds like the clutch is slipping Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-241036 Share on other sites More sharing options...
rsb502 Posted April 7, 2014 Share Posted April 7, 2014 If the revsa are coming up and the speed isnt your clutch be slippin yo, lol! sorry just in one of those moods but yeah sounds like a clutch, see what you got left for adjustment, remember 2" free travel at the top of the pedal and you can adjust the cable and the clutch to get things all back where they need to be if they are out of whack. Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-241039 Share on other sites More sharing options...
Unselor Posted April 16, 2014 Author Share Posted April 16, 2014 It was the range syncro worn out. It's in the shop now and should be finished this afternoon. It was just acting funny I guess slipping in and out making it seem like the clutch. We'll know for sure once it gets back on the road under load but that syncro is definitely shot. Quote Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-242252 Share on other sites More sharing options...
Mack Doctor Jr. Posted April 16, 2014 Share Posted April 16, 2014 I was gonna say synchro. Since it's only doing it on high side and loaded every now and then. Quote Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-242254 Share on other sites More sharing options...
ultratruck Posted April 28, 2014 Share Posted April 28, 2014 You need to have about a 1/2 inch of clearance between the pressure plate and the throw out bearing. Then about 2 inches of free play. Could be someone has just adjusted the free play. If you have that then time for the clutch to come out. Quote Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-243613 Share on other sites More sharing options...
Gmerrill0516 Posted April 28, 2014 Share Posted April 28, 2014 Can't understand how a syncro can have an effect on the system like that. It's either in gear or out right? If the gear were not "in" the engine would rev to the limiter with no load. If it is not shifting related but is happening as you drive and pull harder...I still vote clutch. Classic symptoms. The highest gear has the worst mechanical advantage and is where things typically show up. If you down shift it will work the clutch less hard in the lower gear and will hold the forces necessary to move the truck.If this isn't the case, I'd love to know the mechanics of the problem. Quote Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-243615 Share on other sites More sharing options...
Mack Doctor Jr. Posted April 28, 2014 Share Posted April 28, 2014 Well hopefully he will post what the problem is. Quote Link to comment https://www.bigmacktrucks.com/topic/35324-engine-revs-up-in-high-gear/#findComment-243621 Share on other sites More sharing options...
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