New Clutch Not Working As Expected

[rrzabo1]

I recently have had the clutch replaced on my '98 F150, has the 4.2 six in it and just under 100k miles. I am now finding it hard to shift into 1st gear at idle and once in 1st gear I get a random stutter when releasing the clutch. Seems like I have a limited grab area through the travel of the clutch pedal. I get no grab for the first 2-3 inches and then full grab within 1 inch or so. What do you think happened?

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[WVtrucker]

Check for leaks in the hydraulic system and bleed the slave. Sounds to me like you may have air in the system or fluid getting onto the flywheel or clutch disk.

WV

[rrzabo1]

Thanks WV, I feel pretty confident that is not the issue. I was very careful to keep everything clean. As for a leak that was my first thought. The fluid level is at full, the pedal is good and stiff, not mushy as air would indicate. Pretty darn sure I'm leak free and properly bled. Any other hints?

Z

[adrianspeeder]

Was the slave changed?

[rrzabo1]

Sure was, I changed the Pressure plate, disc, throwout bearing with the internal slave and pilot bushing. A real stumper.

[JMC]

Did you adjust the clutch pressure plate before installing? That would explain the different hight of the pedal. Try pumping the pedal three or four times before shifting. If that helps I would go back and bleed the system again.

JMC

[rrzabo1]

Thanks JMC, I thought that it was considered a "self Adjusting" clutch. What adjustments need to be made?

Pumping the pedal didn't help. Pretty much the same.

Thanks for the help gents,

Z

[JMC]

The factory pressure plate has adjustment. It has to be set during installation.

JMC

[TJIM01]

Originally Posted by JMC

The factory pressure plate has adjustment. It has to be set during installation.

JMC

Oh contrare....There are no 'adjustments' to make. I'm a mechanical engineer for the company that makes 75% of all Ford truck clutches. I don't design them anymore, but I can tell you it's not air in the system. He's right about the 'mushy' feeling he'd have and the pedal engagement would be at the floor - not at the top of the travel.

The symptoms noted would most likely indicate;
1). bent disc / driven plate (from factory or from installation caused by not supporting the trans adequately during instal)

2). Disc is 'hanging up' on the input shaft - did you lube it? The disc needs to be able to slide / float easily on the shaft, so it can back-away from the flywheel when it is released so the input shaft stops spinning.

3). Defective parts (were these 'New' parts? From where? Many companies use Chinese product now, although they calim they don't which identical the original, but functions poorly - we have found our own parts copied, right down to our own die marks from our presses!!) The disc cushion (between the friction material) has a specific dimension it must maintain, like 1.8mm. If this is too high, you get your problem.

Although the pressure plate may 'lift' enough to drive, the disc is still dragging on the flywheel which does not allow the input shaft of the trans to fully stop - that's why it's difficult to shift into 1st. If the disc is bent, same effect.

If the parts were "remanufactured" - throw them out. You can tell by looking at the face of the pressure plate. It should have lathe cut (circular) marks/grooves...not cross-hatch blanchard grind marks.

I could right a book - but this should help you. In any event, you need to take it back out. Sorry. Make sure you use a transmission jack, if you didn't the first time to ensure you don't distort the disc going in.

PS - Some Heavy truck clutches are the only ones which are manually adjusted - although this is going away now too.

[JMC]

From the Ford Shop manual Section 308-1:

1. Note:
The self-adjusting clutch pressure plate should always be adjusted before installation.

Compress the clutch diaphragm fingers.

1 Place (A) the flywheel and (B) the pressure plate in a press.

2 Use a (C) suitable adapter and press the (D) clutch diaphragm fingers until the adjusting ring moves freely.

2. Adjust the clutch pressure plate.

Rotate (A) adjusting ring counterclockwise until the (B) tension springs are compressed.

Hold (A) adjusting ring while releasing the pressure on the clutch fingers.

What is all this about then?

JMC

[TJIM01]

JMC - I wasn't sure, so I checked yesterday and it is in fact our clutch (LuK) in this vehicle. It is highly technical and referred to as a SAC (Self-adjusting Clutch). I checked section 308-1 of Ford's shop manual and as you pointed out they actually do state adjusting this SOP - much to our dismay. This part is preadjusted at the factory and should never require adjustment - except in one case.....where the over-inquizitive installer (or son/daughter or neighbor kid for DIY'ers) decides to see what happens when he stands/jumps on the clutch fingers. Depressing the fingers out-of-the-vehicle will cause the adjusting ring to rotate and the will then require readjusting.

RRZABO1 - Did this happen in your case? In any event, the small horizontal springs on top of the clutch should be compressed..if not, you do then neeed to adjust it as JMC indicated. However, Fiddling with the adjustment as Standard Operation Procedure is a mistake and I would Highly recommend people DO NOT do this, unless the part clearly requires it. Actually, I suggest it be returned to Ford for a replacement instead. We will be contacting Ford and asking that the manual be modified to only CHECK for the proper adjustment prior to install and take necessary steps accordingly.

I admit I was wrong in stating lt. truck / pass car clutches Never need adjusting - this type of clutch is the exception, and then it should be rare.

Thanks TMC for pointing out the problem in the shop manual.