I need help understanding how a firewall clutch adjuster works from thoes who have more experience with them. From what I gather, screw it in and the clutch engages sooner, screw it out and the clutch engages later. How do you know where it needs to be and when to adjust it for clutch wear?

In my quest to hunt down my driveline vibration as mentioned in this thread: https://mustangboards.com/general-te...vibration.html

I have been trying to debunk any possibilities for the vibration. This afternoon I drove the car a bit and then stopped and decided to mess with my firewall clutch cable adjuster. I screwed it in about 1.5-2 turns. This resulted in the clutch engaging slightly sooner, as the pedal is raised. Also, and what surprised me, is that at interstate speeds, it reduced the vibration I have been experiencing. It didn't eliminate it, and I wouldn't even say drastically or significantly reduced it, but it was noticeable. About to where I wouldn't even complain about it if I didn't know that it had just been worse. I only got the car up to 70mph and not the 90mph where I have seen the vibration get bad. So the jury may still be out. The clutch isn't slipping at any point as far as I can tell. Perhaps I was getting clutch chatter?

My setup is: MM clutch pedal adjuster, MM clutch quadrant, UPR firewall adjuster, stock clutch cable, stock clutch (as far as I know).

 

You hit the nail on the head. When you screwed the adjustor in, you increased the distance between the face of the throwout bearing and the fingers on the pressure plate. When you press the pedal down you have to make up this distance plus the distance it takes to move the fingers on pressure plate to release the clutch disc and vice-verca. Decrease that distance (screwing out the adjustor) between the throwout bearing and fingers and the clutch will engage later.

Adjustment is going to be a personal preference thing. I have the Steeda setup on my car and I like my clutch engage later (a little closer to the top) helps when you speed shift.

You kinda have to find the sweet spot. You dont want it adjusted so tight that the TOB is spinning all the time and applying pressure on the fingers causing slippage on the pressure plate and the clutch disc, on the other hand you dont want to adjust it so low that the clutch is trying to pull all the time even with the pedal completely on the floor.

A couple of questions for you
1) How many miles on your car?
2) Any noise from the bellhousing area?
3) Did you notice this problem only after the tq. arm install?
4) more to follow

 

That's a lot of good information. I need to read a bit more on the fine details of the clutch but that really helped.

-62K miles, got the car when it had 29K, so I figure the clutch is stock.

-There's not much nise that I can determine is coming from the bellhousing. Clutch engagement and release is all pretty smooth, no crazy feelings through the pedal. If I'm at about 70mph and let off the gas to let it slow down I get low sounding growl for just a second. I can't remember if it happens only when the car is in gear or not. Every once in a while I can hear the gears spin down (what I think it is).

-Everything I've descibed so far has happened before the Tq. Arm. I think I've just noticed it more lately becuase when I installd the Tq. Arm I was at my parents house in Texas. They have a lot more wide open roads with no one around, so I was able to take the car up to 90mph and really notice the vibrations. The Tq. Arm does transfer vibrations into the car a bit more since it's more rigid and mounted right under the front seats.

 

With your gear and wheel package, how many rpms are you running at 90 mph?
Once you find this number,would it be possible to drive the car at this rpm in each of the gears and see if the vibration is more notible in a certain gear?

If the rpms were lets say 3200, have the engine and driveline at operating temp, drive the car at 3200 rpms in first gear and check for noise. Then 3200 in second gear and so on... check for vibration in each gear.

I am trying to determine if the vibration is in the engine or driveline or even a tire maybe out of round.

 

That's some good thinking.

I've never looked at the RPMs when I'm at 90mph, but probably somewhere around 3500-4000 rpm at 90mph. 3:73 gears, 3650 trans (either in 4th if I'm still accelerating or 5th if I'm cruising), probably a 26 inch tire. I'd have to find a calculator if I didn't go out and do it myself. I don't think it's just at a certain rpm though, in first or second if I ever get up in the high rpms I never notice a vibration. It's seems it gets worse as speed increases, but that doesn't really explain how me adjusting the clutch improved it a bit. I've thought about the wheels being out of balance, which would be cheap to fix.

 

My thought was that if the vibration was consistance in all gears at that rpm then the problem would be in the front of the car i.e. harmonic balancer, pilot bearing, input shaft bearing, or something in the clutch. If the vibration was in the higher gears then the problem would be in the rear of the car i.e. u-joints, driveshaft. wheels or tires, or maybe something in the rearend.