Common

Hopefully I'm just noticing something thats always been there.

But in 4th and 5th if I'm at 1600 RPM and mash - its seems that the trucks RPM's accelerate too fast from 1600 to 2100 then the RPMs quit climbing as fast at 2100 (yeah, I know the fuel is cutting out)

But if I lug it in 4th and 5th it will hold everything until 1600 or so...

Dunno, seems like its maybe slipping... never had a clutch slip on me to be honest.

What I was told is that I would really notice it.

Clutch in sig.

cmac

its kinda hard to tell without driving it but it does sound possible... on that note when a clutch goes it usually goes quick so if your not sure now you will be soon. when mine went out last time it was kinda hard to tell until it was REALLY slippin!!

Common

Would the truck still accelerate while the clutch is slipping?

It seems like its one of those things I obsess over...

Dunno what else it would be though...

I'm weird sometimes.

RPegram

Any time you have a manual and the rpm's go up on acceleration without comparable gain in speed, clutch is slipping. Sometimes it starts out just a little, but then quickly gets worse. Normally clutches start slipping in higher gears first. Even a new clutch can start slipping if it is rode very much and glazed over. Heat causes the glazing and can happen very quickly.

Common

Anything one can do about glazing?

or once its glazed over... thats it?

I really don't have the money or time for another clutch...

I took it out for a drive today, and its not really doing it...

I don't know... no smell or anything like that...

I wish one of you could drive it...

Vent on the bellhousing is clean... no friction material or dust...

As you can see, I'm not too informed on the clutch assembly.

cmac

it is possible for the truck to still accelrate while the clutch is slipping. however it wont accelerate as quickly. about the only thing you can do to prevent glazing is to avoid sliping the clutch when you are taking off or shifting. a clutch is most vulnerable (sp?) in the first 500 miles or so. once it is glazed over i beleive the only thing you can do is replace it. i'd drive it for ya but 7 1/2 hours is a little bit to far away.

Dartmouth 12V

To help you understand clutch slip, here is my explanation.

When a clutch starts slipping, it goes from using static friction to kinetic friction. There is still friction present so you are still putting power to the wheels, just not as much. The power that doesn't go to the wheels goes into the clutch as heat which will accelerate the issue. Since more power is going to the flywheel than is going to the transmission, the engine rpm will accelerate at a greater rate than the vehicle is accelerating. There normally is a linear correlation between engine rpm and speed but that no longer holds true when the clutch is slipping.

The reason that people observe slipping in their highest gears first is that it has to do with how much torque goes through the clutch. If you think of torque as a radius times a force, your radius stays the same and your force goes up as torque goes up(it is actually a sum of all the forces over the area). In higher gears, you can put a greater load on the engine which will allow you to put out more torque. This happens at the torque peak of the engine. It is important to understand the difference between engine torque and wheel torque. Engine torque gives you the force through the input to the transmission whereas wheel torque tells you much force you are putting into propelling the vehicle. If you want to accelerate quickly, downshifting and running a higher rpm is better for most power/torque curves.

I know this doesn't answer your question as to whether the clutch is slipping but with a better understanding of how it works, hopefully you will be able to diagnose it a bit better. I drove my dads car a few years ago and noticed that the clutch was slipping so he took it to the dealer who said that it wasn't. It turns out that the dealer was only giving it a lot of throttle at really high rpms in low gears where there wasn't much torque being transmitted. The next phone call I got from my dad he was unable to drive up a hill since it was slipping so bad.

torquefan

Accelerate the truck at 1600 RPM, and get it up to 2100 by allowing it to slip. Now take your foot off the throttle and see if the tach needle drops or stays steady. If it isn't slipping, the road speed should hold the tach steady. I find it easier to spot slippage on decel than when trying to accelerate. Another trick I use is to perform the above test while in 4WD, then you know you're feeling actual clutch slippage, and not just tire slippage.

RPegram

If it were mine, I would drive it until it got to slipping so bad in fifth, it was extremely obvious and you have a hard time accelerating. Try to take it easy in 4th and 5th and it will probably last a lot longer.

crewcabxlt

unfortunatly the luk pro gold in my experience wont hold up to the torque of a mildly modded cummins

Yellow Yota

Keep your RPM up when you need the power. Not lugging in a high gear will extend the clutch life.
A friend has (or has had a couple) Luk Pro Gold units in his truck. Same problem. He needs to upgrade to a SBC, but dosn't have the extra money either. And, he says that his Luk's are lifetime warranty. It's just a pain to swap out every year.

Common

I hope its lifetime warranty.

I'll have to check on that.

If I lug it, the clutch won't slip at all...

I don't even know if its slipping...

I should have gotten a SB.

Common

Taled to Peter today - gonna be getting an OFE soon...

Common

Do I need to get a hydraulic upgrade?

patdaly

Shouldn't with an OFE.

Might want to spring for a DD3250........ How much more power are you going to add? I don't remember if you tow much either.