vintintin

I have a 2007 5.9L with the six speed manual. It has just under 90,000 miles on it. It's never given a bit of trouble until yesterday.

Pulling a 30' gooseneck trailer (6000lb empty) and attempting to pass a slowpoke on a two lane highway, the RPM suddenly raced past redline as if I had disengaged the clutch. It acted as if it hit a rev limiter, dropped down to around 1200 RPM as if the engine had died and then began to run normally. It did this twice yesterday while accelerating, under load, passing other vehicles. Today, with the trailer loaded (16,000 lbs total) on a long uphill pull, it did the same thing. No heavy acceleration or heavy throttle when it did it today. Just the strain of a long hard pull.

It acts like the clutch completely disengages, the engine races to a point where a rev limiter kills it, and then it slows to a reasonable RPM before restarting and running properly. While decelerating, you can feel the engine compression holding it back, so I am confident that the clutch is engaged and holding. No problems at all with the clutch otherwise.

There is no "seat of the pants" feel that the clutch is slipping when the RPM runs up. It feels more like the fuel supply has increased ten fold and we are off to the races.

Any ideas? All help would be greatly appreciated.

SpeedyWS6

Could be the fuel control actuator hanging. Or the sign of an injector at the first stages of failure.

sr4440

so your engine RPM's under load and your truck goes nowhere?

your clutch is shot, it's just a matter of time until your not going to move at all. the only place a engine can "slip" and reengage without damage, is the clutch.


Joe

SpeedyWS6

X2 I missed the part where you didn't have the clutch pushed in.

no_6_oh_no

If you increased the fuel that much the truck is going to accelerate or try to until the clutch lets go and starts slipping and you WILL smell it. Not to mention the BBCOD its going to lay down.

Are you SURE the engine is actually reving? It would be very noticeable and the truck is going to some moving and jumping.

The dash gauges in thse things are not really indicative of actual engine operations and can go bad giving false readings. If your feeling\hearing no physical results of dumping that much fuel into the engine its either the cluster controller or the bus going bonkers.

vintintin

Guys, Thanks a million for the replies. Each of your answers have encouraged me to move off in different directions with my thinking. lol

I am beginning to think that the clutch might be slipping, since it is occurring under heavy load. It makes sense that at speed, with a load, under heavy throttle, the engine torque could actually overpower the clutch. This would explain the tach indication of revving past redline, the resulting shutdown, during which the decrease in engine torque would allow the clutch to re-engage. The drop in RPM would allow reset so the engine fires again and pulls normally.

My dad was with me when it occurred and his take on it was pretty accurate. He said it acted like an automatic transmission when you floor it at speed and it downshifts. You hear the engine pull, feel the jerk when it shifts, followed by engine rev and acceleration.

Funny thing, no_6_oh_no, I never have smelled the clutch burning. What is the BBCOD? I am pretty confident the engine is actually revving, however there is room for error here. It happens very quickly over just a couple seconds and I could be misinterpreting what I am seeing, hearing, feeling, etc.

With under 100,000 miles (warranty thoughts) on the truck, do you think a dealer could put it on their analyzer and tell me anything?

Again, guys, thanks for the help.

no_6_oh_no

Big Black Cloud Of Death.

If you are feeling the the truck move and hearing the engine wap up I would guess the your DMF and clutch has issues. Thats kinda the norm with them when they go bad.

SpeedyWS6

When I burned up the stock clutch in my 07 I never once smelled it.

Usually when a clutch starts to slip it is more noticeable in overdrive as that gear puts the most strain on the clutch under a load.

Are you backing off the throttle to bring the revs down?

PoorMansCat

I wouldn't ask for any warranty consideration on anything to do with the clutch. The standard response is that the clutch is a wear item and is not covered by warranty.
If it were mine, I would simply take this opportunity to install a street dual disc from a reputable company such as South Bend Clutch.