What Causes Clutch to Drag.

[jhv48]

If you've read my previous posts, I have a TKO 600 that grinds going into reverse, no matter what you do first, and is tough to slip into first gear at a stop. All other times, it shifts beautifully, both up and down. Ran fine for 1500 miles. Problem just started.

I checked and replaced the slave, master cyl. bled the system. The slave pushes the fork about 1 1/2 inch. No leaks or air bubbles. Both are 7/8 inch bores. Standard SPF units.

Clutch is properly adjusted so it engages about 2 inches from the floor. No slipping is present.

We pulled the trans and examined the clutch. Everything looks fine. No warps, no oil, no glazing, nothing appears bent, warped or abused.

So, what else is there. And, like I said, the car only had 1500 miles on it of all street driving when the problem cropped up. Tremec said that it's not the tranny. Got to be something wrong with the clutch.

So, what do I check next? I really don't want to replace all the clutch components, but also don't want to button it back up and have the problem persist.

Experts feel free to float a solution here. I have a day or two before we put it all back together.

SOLUTION

Pilot bushing was causing the input shaft to turn when the clutch was depressed, thus causing grinding in reverse and difficulty pushing lever into first from a stop.

[Got the Bug]

Replace all of the clutch components (you asked to float all solutions). Also, make sure you are using components that are well tested and are standard for a Roush/TKO set-up (guessing McLeod?).

[tkb289]

Jim,

I am not an expert ( just for the record ).

This is just a thought, but take a closer look at the pressure plate, in particular the 'fingers' that are pushed by the throw-out bearing. If you think about it, the pressure plate is the one moving piece that you have not been able to observe under operation.

If you have the time and ambition ... here is an experiment.

Take the whole flywheel, clutch disc and pressure plate assembly off the motor (be sure to mark how they were on assembled) and set it up in a Arbor press.

- Using a steel disc in place of the throw-out bearing, use the arbor press to gently actuate the clutch.

- Look to see how consistently the pressure plate un-clamps and clamps ... does it move a consistent amount each time? I am not sure how much it is designed to move, probably not very much, so you might have to use some feeler gauges for a more accurate measurement.

Hope this helps ... Best of luck.

[Ibr8k4vetts]

Sounds like your Throwout Bearing is not moving far enough in to engage the clutch! (in my case I had to find a thinner clutch disks) You might need a longer piston in your throwout bearing set up. Good luck! Mine was a nightmare

[xlr8or]

Because you are pushing the pedal so far down to be able to shift try this:
Adjust your clutch so it disengages sooner in the pedal travel. Instead of 2" off the floor, adjust so it's half way up or so... As you push through that range test the shifting. Assuming as you said the clutch disk is not worn, and it improves it's either problem solved or the pressure plate is the likely culprit.

[legenmetals]

Has the pedal become harder to depress,or does it have a tighter range of travel? Mine did and it had few miles on the disc and pressure plate. I replaced the three arm pressure plate(forget what they call this type)to a diaphram pressure plate with a new clutch disc and this solved my problems with engagements.

[Ralphy]

Have you checked the alignment of your bell housing? I was also reading at another board that this person had a warped BH.

Indicate the bore for the trans and the mating face of the bell housing.

[Rick Parker]

jhv48: What initiated this problem, or did it gradually arise. Has a part within the clutch assy be changed?

What causes a clutch to drag and 1st & reverse gear to grind is the input shaft within the transmission is still spinning (pedal depressed) caused by the pressure plate not fully releasing the disc which is still propelling the input shaft and the 1st gear syncronizer assembly struggles to equalize the speed of the stationary gear with that of the one that is spinning, hence the clashing of the gears. If you turn the engine off it will easily slip into 1st or reverse, right? OK this is over simplified but something has changed. Try a 15/16 or 1" Master cylinder, they are easier to change than finding a slave that will fit your set up. Be sure to "bench bleed" the master cylinder before installation, air bubbles within are all but impossible to remove once installed. This will provide your slave a little more travel which is what you are in need of.

[Barnsnake]

Your pilot bushing (or bearing) could be bad or backed-out of the crank.

[Ralphy]

Yes sounds like somethings draging on the input shaft.

Originally Posted by Barnsnake

Your pilot bushing (or bearing) could be bad or backed-out of the crank.

[Tony Radford]

Sounds like you don't have enough travel to fully disengage the clutch (been there). I'm running a long throw Ram and I eventually replaced my master with a longer throw unit. My suggestion is that you ajust your mechanics so that it fully disengages the clutch even if it starts slipping under load. If you can do that, you will have confirmed that you simply need more travel. It's not the easiest issue to resolve, but at least you'll know what to concentrate on.

[blykins]

I would check (in order of importance):

1. Bellhousing is in alignment.
2. Pilot bushing isn't worn.

Also, watch about a long TOB travel with a diaphragm pressure plate...you can push them too far.

[jhv48]

Originally Posted by Barnsnake

Your pilot bushing (or bearing) could be bad or backed-out of the crank.

That's where I'm headed now. The clutch travels full length, no signs of warpage, slipping or any other disc or pressure plate or flywheel defect. Fork travels the full range.

I'm inclined to agree with the pilot bearing being bad and not allowing the input shaft to cease rotation when the clutch is depressed.

Will talk to the installer today. I'm going to have him remove the pilot bearing and fit it to the input shaft to see if it binds and then replace it. My bet is it will bind slightly. This $15 part is going to cost me $1500 to replace.

Will let you know if you were right.

[CobraEd]

I have always understood than any clutch should be adjusted so that there is about 1" of play from the top of the pedal, not 2" from the floor. If you adjust it to 1" from the top, you will be disengaging the clutch much further and may eliminate the drag.

.

[RICK LAKE]

jhv48 JH couple of things that need to be checked, Lets start with air gap, you need .038" to .050" with the clutch pedal engaged. This measure ment depends on the pressure plate being a diapham or 3 finger setup.
If you have the correct clearance then you are looking at bellhousing alignment to see if it is centered on the block. If not under .003" you need to have it centered. Lakewoods are real bad for off centered. Once this is done have washers welded to the bell to keep it centered if you every have to pull it again. If you break the motor and get a new motor, remove the washer and center the bell housing on the new motor. QuickTime bell housing are very close to being centered on most blocks.
For pilot bushings, I like bearings better but bushing work. You have to make sure the bushing is not too tight on the input shaft of the trans. Use a little grease on the bushing when the trans goes back in the car. If this all checks out you are looking at the trans for internal problems. 1 other thing to check is the length of the input shaft of the trans. If you have a GM input shaft, it could be too long and rubbing on the end of the crank shaft, and wearing out the thrust bearing for the crank. If you are running a lakewood bellhousing, some trannys need .380" cut off the end of the input shaft. The teeth of the input shaft could be also dragging on the bushing too. Last idea is to replace the fluid in the trans. I am going with you have worn out the clutch enough to have it drag. Rick L. Ps you can also over extend the pressure plate in the clutch and cause the same problem. Your clutch pedal may need a stop too.

[jhv48]

The tranny was sent to a transmission specialist and proclaimed in fine working order.

Shop is leaning toward the pilot bearing, bellhousing alignment.

Will let you know as soon as I know.

[CobraEd]

Jim,

Bear in mind, no matter how bad a pilot bearing is; (worn, galled, dry, tranny shaft too long and bottoming on the crank), when you are stopped and have the transmission in gear (1st), the input shaft is not and cannot be spinning and you should be able to put the transmission in any gear you want easily. Including reverse. Don't want to push it, but I still think that setting the pedal 2" off the floor is not right, and you are not disengaging the clutch fully.

Regards
Ed

[Bobcat]

I agree with CobraEd .... you measure clutch free play from the top ... not from the floor up .
Have you jacked the car`s rear end off the ground and checked to see if there is any clutch dragging ?? Easy thing to check and you can do it by hand by turning the rear wheel as you push the clutch in . If dragging , you should be able to hear it as the disc contacts the flywheel . Also , if you have a diagram clutch , you can have too much travel and push the fingers over center .
That`s the way Tilton says to set their HTOB .... push the pedal in until there is no drag and then 1/4" more to set the pedal stop . Hope thi s makes sense as the Oxycodone is finally starting to work .

Bob

[Woodz428]

I have to go along with Ed as well. At 1500 miles of street driving the clutch should be just getting worn in enough to need adjustment. Although it would likely get "tight", depending on the pivot point of the arm. That's another possibilty, if the pivot is adjustable and wasn't locked down tightly enough that could have vibrated out. The fact that it worked fine for 1500 miles and then began acting up, makes me think of adjustment. There was no comments about any "event" that would have created it. A few pics would supply more info than several posts could.
There is absolutely no possibilty of air in the system? I always c-clamp my slave while bleeding, it eliminates the clutch movement and makes it bleed like a brake system. It also seems to make the process much faster.

[jhv48]

As a folow up, I adjusted the clutch to catch everywhere from the floor to the top of the pedal. No difference. I adjusted the slave from no pressure to slightly slipping. No difference.

Something is causing the input shaft to continue turning when the clutch is fully released.

Only thing left is the pilot bearing.