Is my clutch going out?

[Fear This: Cummins!!]

Received a call today that My '13 is on the train and will be here August 8th. There after, I was heading down I-81 on a flat stretch in 6th gear with my '06 mega cab, when I hit the go pedal and was sure that I heard the rpm's go up and the truck speed not increase. I got out of the pedal immediately and shut the radio off and hit the go pedal again. I was sure again the rpm's moved and the truck ground speed did not respond. I shifted into 5th to head into the pappy lane and get off the highway. I got into the pedal in 5th and the truck took off. I toyed around for the last 6 miles of the trip with no incidence. Later in the day I pulled a hard grade with no problem. Everything felt fine in all gears. I had one last grade before my next destination that is 1/2 mile long. I normally pull in 5th at about 55 mph. Half way up I heard the rpm's climb and the truck did not go faster. Got out of it and then hit the pedal again heard it climb in rpm but no gain in speed. I then shifted to 4th and it pulled fine. Left the trailer drove 15 miles home. Can not make it slip. Certainly seems like the clutch. She has 80,000 miles on her. About 8,000 of those miles are at a GCWR of 25K. All other miles are empty on the Interstate. The edge EZ is always on the low position. Any thoughts would be appreciated. This truck is already sold so this throws a twist into things.



Thanks, Jared

 

[RVTRKN]

Before my SMF replacement, I had a problem with the flashing of the ECM in 09. The regen program causes a sluggish throttle and then surges after 2K rpm and caused my clutch to slip while climbing a grade at 23K GCVW. It was never the same and slipped with just adding throttle on flat roads. The SDD 3250 stopped that, so if your running a programer remove it before the sale, unless its a family member. You can always discount the cost of the clutch replacement.

 

[GCroyle]

Jared,

Smell anything after any of the episodes that smelled like friction material overheated?

Increase in RPM with your foot off of the clutch pedal must result in increase in MPH proportionate to the gear selected. Gears don't slip.

Gary

 

[mfurrh55]

I have 118,000 miles on my 07 5. 9, and mine has done that in 6th gear since new if i get on it hard, so i just back off and drive it without jumping on the pedal hard and it pulls loads fine, it's just that DMF causing slipping is all, monte

 

[GCroyle]

it's just that DMF causing slipping is all, monte

Monte,



I've taken the G56 series DMF apart, it does not have an internal friction clutch. It is not capable of independant slipping. The 7. 3L up to 1997 did in fact have an internal torque limiting clutch with friction material. We used to hear once in a while about a "tech" that would dip the entire 7. 3L DMF and then ask why does it slip? He contaminated the internal friction material by dipping it.



The last DMF design that I have taken apart that has an internal torque limiting clutch was the end of the DMF's used in the 7. 3L in 1997. The lower left corner of this pic of a 7. 3L DMF shows the (L-R) 2 friction plates with the ears that drive the damper springs then 2 bellevile springs that provide the force that pushed the friction material against the friction surfaces. One of the friction surfaces is the back of the secondary FW top L and the other friction surface is just above the center of the pic and the actual friction surface is visible just outside of the raised center section. IIRC I counted about 120 individual components down to the rivets to make this style DMF.

 

[mfurrh55]

Monte,

I've taken the G56 series DMF apart, it does not have an internal friction clutch. It is not capable of independant slipping. The 7. 3L up to 1997 did in fact have an internal torque limiting clutch with friction material. We used to hear once in a while about a "tech" that would dip the entire 7. 3L DMF and then ask why does it slip? He contaminated the internal friction material by dipping it.

The last DMF design that I have taken apart that has an internal torque limiting clutch was the end of the DMF's used in the 7. 3L in 1997. The lower left corner of this pic of a 7. 3L DMF shows the (L-R) 2 friction plates with the ears that drive the damper springs then 2 bellevile springs that provide the force that pushed the friction material against the friction surfaces. One of the friction surfaces is the back of the secondary FW top L and the other friction surface is just above the center of the pic and the actual friction surface is visible just outside of the raised center section. IIRC I counted about 120 individual components down to the rivets to make this style DMF.

So, what is the slipping sound then?My truck has done this since it was new, I've pulled loads over mountains in Colorado and new mexico weighing 28,000 GVW, never slipped until i give a fast throttle empty weight

 

[GCroyle]

Monte,

W/O being in the truck and you demonstrating, any disproportionate increase in RPM vs MPH has to be clutch slipping. If you experience it again, pull over and shut down and try to get a whiff of clutch perfume as a nose confirmation.

 

[Fear This: Cummins!!]

I did not smell anything. Could it be the pressure plate giving in?

 

[Fear This: Cummins!!]

I assume this has nothing to do with it, but I used Low 4x4 immediately before this happened. It was 2 miles down the road later that this happened. I am guessing this is a coincidence.

 

[RVTRKN]

The Ford DMF is why I thought the Dodge DMF slipped to protect itself. When I inspected my DMF and clutch I found it somewhat worn but not bad enough to cause slipping like it was doing. I believe the ECM when in regen under 2K is detuning the engine to prevent soot and over 2K it surges, which I believe adds power to the engine but more than the stock power. It is why my truck slipped the clutch when empty, if getting on a freeway, and accelerating on a grade loaded, even with a small trailer, it could slip, but only in regen. Thats why I chose the SB SDD 3250 which is capable of holding 550-650 HP, so far it hasn't slipped when in regen, but I have not tested it loaded on a grade yet.

 

[GCroyle]

I did not smell anything. Could it be the pressure plate giving in?

In simple terms, the pressure plate clamps the disc against the flywheel and does not allow it to slip, it must be locked at this point. When you push on the clutch pedal the clamping force is removed from the pressure plate and the disc is no longer clamped, you are free to shift and select a gear. The engine power has been disconnected.



If a pressure plate is going out and allowing the disc to slip it might only be a short time before the extreme heat destroys the facings and its clutch time. Overheated clutch facings have a nasty smell, similar to the last time you smelled overheated cooked truck brakes.



You as the driver control the clutch releasing (pedal on floor) to disconnect the engine from the trans and then the time spent in the friction zone (pedal coming up, disc is accelerating from zero RPM at a full stationary position to engine RPM) and finally fully engaged foot is off of the pedal.



Keep in mind the friction zone time is when you are "actively spending" the clutch. Heat from friction is being created while engaging and causes wear. Keep the friction zone time to a minimun and keep the RPM differential low at engagement ( think of how easy it takes off in 1st gear at engine idling, uses almost no clutch wear) and this will extend your clutch life. Any time I have a newbie in my truck I demonstrate the Cummins power with a 1st gear pullaway with the engine at idle. Showed an ex employee that had an Eclipse car background how out our old 12V with a 40' car trailer just at idle took the entire load w/o a whimper engaging at idle and getting going. His Eclipse would have stalled the engine trying a similar engagement with no added load.



Can't comment on how regen feels, my trucks don't have it.