mr. ed

Hello again, guys. About a month ago I posted a thread on this forum regarding my clutch slipping right after I changed the fuel filter. I know that had nothing to do with it but I had forgotten to mention that I had recently enabled the high idle feature and now believe this may have had something to do with it. Let me explain:

When I was in Victoria, TX I grounded the particular wire per instruction on this forum. To my satisfaction, the high idle feature worked fine. I spent about a month there and drove the vehicle without any problems. I then proceeded to tow my fifth wheel trailer (est. weight about 12k) to Fort Stockton, TX, again without any problems. However, during most of the trip to Fort Stockton I didn’t use cruise control. The reason I mention this is because I believe there is a correlation between the high idle feature and cruise control (I‘ll explain momentarily). As we know, the computer controls both these functions and it’s my opinion (just an opinion, mind you) that under certain conditions it’s possible for the two features to conflict momentarily, thus causing a sudden spike in power and concurrent clutch slippage.

The problem first showed up shortly after leaving Fort Stockton when I had the cruise control on and the G56 tranny in 6th gear and I tried to pass a truck that was entering the interstate. I applied moderate pressure to the accelerator and all of a sudden the RPM’s shot up briefly and I could hear a banging noise from the clutch area as the clutch disengaged and then re-engaged. Being concerned that I was going to get stuck on the road with a bad clutch (it was Christmas day) I drove very carefully to Deming, NM without further incident.

When I left Deming bound for Tucson the problem reoccurred. This time I wasn’t passing anyone but accelerating slightly as I approached a mild grade. Suddenly. it appeared that I lost the clutch completely. I managed to coast to the shoulder and sat there for a few minutes, figuring I’d have to call for help. I decided to try to move the truck anyway and found that it was OK so I very carefully drove into Tucson. Now, here’s why I think this situation had something to do with the high idle feature:

While in Tucson, I decided to add a toggle switch between the wire that I had grounded and ground (see picture). I leave it in the off position while towing with the cruise control on. Well, I towed my trailer from Tucson to Yuma (about 220 miles) without incident. The clutch showed no sign of slippage. So, you tell me…is this just coincidence or is it possible that high idle and cruise control can conflict with each other unless high idle is completely disabled as I described? (BTW, I had the clutch inspected in Tucson and there was no sign of oil contamination, as I originally suspected). I know a lot of this may not make sense but I can’t argue with the fact that the slippage has stopped and it appears to have been caused originally by grounding that wire without providing a switch to isolate the wire from ground when high idle isn’t needed. I’ll leave it up to you experts to figure this one out.

The switch is easily installed in the little pop-out panel located just above the emergency brake

AirGrabber

I dont by it. Nice theory though. Reason i say this, is, your clutch is a coupling between your trans and your engine. If the engine is spinning 1500 rpm your trans input shaft is spinning 1500 rpm with the clutch engaged. Unless your clutch is slipping for what ever reason. What ever caused it to slip is a whole different issue. It might be you rest your foot on the pedal while driving, oil or something got onto the discs or flywheel. Defective clutch ect..... When you let your foot up off that pedal and hit the gas, regardless of what ecm is telling your engine to do, if the clutch is good, your transmission is going to do it.

BroncoHound

Interesting report. I can't remember with my '08 which came first: the enabling of high idle or the slipping of the clutch (although i have not yet experienced any slipping to the degree that you describe). I might have to put a toggle switch of my own in there just to be on the safe side. I don't quite see how a computer function could affect how the clutch links the engine to the transmission, but i am not saying it doesn't happen, either.

I would be interested to hear any updates you have as you log more miles on the truck as to whether or not you continue to be slip free or whether it was a temporary leave of symptoms.

mastercaster

coincidence is definitely what i vote. the high idle can't operate unless the emergency brake is set. that eliminates the idea of it from coming on in while motion. all i can say is my clutch used to slip all the time, and hasn't slipped once since putting a real clutch in. i use my my cruise all the time, and have never had any "spikes" in power. and the high idle won't run the rpm's high enough to have ever slipped my clutch anyway. seeing as how the high idle feature stops rpm's at 1500, i only used to see slippage in the mid-upper 2k range and up. sorry mr.ed, i am glad your clutch has been working lately, but many folks have had trouble with the stock clutch and it is a known weakness. that's why our trucks come from the factory detuned. they're running at the max. put a good load on it, or any extra power and it's over.

Totallyrad

Mr. ed, you will notice clutch slippage in your higher gears before you'll notice it in the lower ones, especially when towing. Remember that your engine's peak torque is in the 1500-2000 rpm range. If you apply a moderate amount of throttle, like your cruise would, in that rpm range you can over power your clutch if it's nearly worn out or if it's glazed.

As to the banging you reported, I'm wondering if you've had a spring let go in the pressure plate assembly.

Jonrob41

Gotta go with the majority on this one....All the needed Dodge parts required to do the the grounding is called a CLUTCH UPSTOP/UPSTART SWITCH it is a two wire switch that is normally closed with the clutch pedal at rest. When you depress the the clutch the switch then goes open breaking the ground and turning off the HIGH IDLE feature, However when the emergency brake is released the system is also disabled and will NOT work. So I would have to go with the NOT so good news you have over powered the clutch and caused it to slip. I realize that isn't what you want to hear because the expense of the clutches that will solve your real problem are quite expensive. I too really don't want to hear it as I just got a NEW to me 07.5 with only 15K and its for the purpose of towing our 5ver and I do know I will have to make the upgrade to a Southbend clutch alot sooner than I would prefer.

mr. ed

Thanks for the input, guys. Like you, I don't fully believe that the switch installation was the real problem solver. All I know is that it SEEMED to work. Concerning the clutch pedal switch (which the dealer would normally install), I wonder if that switch somehow resets something in the computer and my addition of the hand-operated switch does the same thing. Again, just a wild guess. Anyhow, I'm glad all appears to be OK (for now).

Here's something else I'll throw into the mix, which might just prove you guys correct: I was facing a pretty strong headwind heading west out of Fort Stockton when the problem first occurred. It's possible a very strong gust hit just as I was accelerating in 6th, thereby adding extra drag. Now, that makes more sense. Still, I'd like to believe what I did by adding the switch did some good. It surely can't hurt knowing that the high idle is positively disabled, although I understand your points about the emergency brake needing to be activated. I'm going to experiment tomorrow and see if I can run the high idle with the emergency brake off, just in case my truck has some kind of fluke in it. If it doesn't, then I'll know that my theory is no doubt incorrect. Thanks again for your responses. It's nice to know that there are some pretty knowledgeable people out there, especially for a new diesel owner like me.

Totallyrad

After reading your last post a thought popped into my feeble little brain. Regardless of whether your manual high idle is kicking in and interfering with the cruise, the stock engine should not be able to over power the stock clutch unless there is a problem with the clutch either due to wear, glazing, a malfunction of the pressure plate or a lubricant getting on the surface of the clutch.

BroncoHound

In a perfect world, that would be true. However, this particular LUK clutch behind the 6.7L can slip bone stock and straight off the showroom floor. The CR 5.9L was pushing the limits of what this clutch could handle when the G56 and this clutch were first introduced. With the added power of the 6.7L, the clutch is without a doubt the weak point of the driveline.

mitternocht

I agree, it doesn't take much 5.9 tuning before you are out of luck with the LUK. The 6.7 should overpower the stocker in short order.