M5OD swap and clutch pressure plate

[Jon M]

Hey folks!

Dolly (the 1984 f150, 4.9 i6) is coming along. Much slower now that it's boiling outside, but I still find a few hours here and there in the mornings. Well I'm having a little trouble with the M5OD swap. And specifically the clutch parts that I'm replacing. This is very much due to my inexperience so I need someone with a little more grey in their beard than I to educate me.

I purchased a standard replacement clutch kit from M-Pact (for a 1992 F150 with a 4.9 engine). It comes with the pressure plate and the pad and a slave cylinder. The cylinder went on fine and after putting on a new fly wheel I got to the task of installing the pad and pressure plate. well once I started tightening down the bolts attaching the pressure plate to the flywheel I noticed that the metal where the bolts connect does not sit flush. Here's a picture:



I tightened it down just to see how it would respond and I'm seeing that the splines on the pressure plate (where the throw-out bearing of the master cylinder connects) bend inwards with the pressure applied. Pictures below. This feels not right to me but I admit that I haven't fully wrapped my head around how the pressure applied by the master cylinder works. None of the videos on Youtube (and there are plenty on this topic) mention that you have to cinch the pressure plate down against the spring of the mechanism inside. I made sure to orient the clutch pad correctly as I know if it's installed incorrectly it will wear down the pressure plate, so I can be sure that is not the issue at play here.

So could someone explain this to me? Did I get the wrong kit or is what I'm seeing normal?

Before tightening


After tightening to flush

[ArdWrknTrk]

I can only think the stack up is too much, or the pressure plate too shallow.

There aren't any pedestal mount flywheels.

[Jon M]

Ok so I'm not crazy. I suppose this means I need another clutch kit. Can you recommend any brands so I can avoid dealing with this a second time?

[ArdWrknTrk]

You're not crazy.
That's how a clutch works!


I've always used Luk, or Sachs (which is a division of Zf)

Well... I've used a few custom clutches in competition and VERY healthy street cars, but those aren't pickups and only see power 10 seconds at a time.

I have a Luk clutch in my truck right now.  
It replaced a Luk that I installed in 2008, and was still holding fine
(but I needed a ring gear, and I'm not putting a 15 yo clutch back in a 4x4 460....)

[mat in tn]

whether crazy or not we will leave off the table. the clutch operation is such that it works like a bunch of see saws arranged in a circle. each one attached to the clamping ring at the outer edge and having a free end in the center. the center contacts the throw-out bearing mounted at the slave cylinder. as you press the clutch lever it compresses fluid inside the master cylinder, which in turn presses the slave cylinder to move outward pressing on the ends of the clutch pressure plate levers causing the pressure plate clamping ring to move away from the flywheel allowing the clutch to let go of the clutch disc. the flywheel and pressure plate being mounted to the engines crankshaft while the clutch disc is slipped onto the input shaft of the transmission allows both engagement and release of the clutch. the simple fact that you were noticing what seemed to be an improper fit was just "loading" the springs of the pressure plate. it takes a fair amount of clamping load to avoid slipping. slipping is what kills clutches. avoid excessive feathering of the clutch while driving also.

[ArdWrknTrk]

If there was no spring preload there wouldn't be any clamping pressure applied to the friction disc, and no way to make up for wear.

[Jon M]

Mat in TN, thanks for that description. If I'm reading you right, then the gap I'm seeing is intentional and I need to cinch down those bolts. Because depressing the clutch is what pushes those splines in which release the pressure between the Pressure Plate, the Clutch Pad, and the Flywheel, correct?  No need to buy a new clutch kit... right?

[mat in tn]

you are on it! torque the pressure plate bolts to spec. this will clamp down on the clutch disc as it is the normal position. abnormal would be with your foot holding down the pedal holding the clamping ring off the disc but heavily against the pressure plate springs ready to clamp as soon as you let off.

[ArdWrknTrk]

Be sure to use the pilot tool correctly.