Hydraulic clutch pedal question

[NukeBass]

Back when I had my 73 Duster restored I had the drive train swapped and had a Keisler perfect fit kit (TKO 500) put in it. This came with a hydraulic clutch setup. I never liked the clutch pedal in this car. The way it is setup, i have to push the pedal as far as it will go and it still will grind going into reverse sometimes. Plus I am short so I have to sit a little closer to the wheel than I would like to get the clutch all the way in. The guy that did the work said the pedal wasn't adjustable because it was hydraulic. I didn't really believe him, but only now started looking into it.

Since Keisler is out of business I can't ask them any questions. I also don't have any of the installation instructions since I didn't do any of the work. I looked on Silver Sport Transmission's website, since they bought the perfect fit kit rights, and their instructions say to install the pedal connection, in most cases, to the stock location. My pedal is attached (see below) near the middle of the pedal shaft when the service manual says the mechanical clutch rod would have connected to the topmost post above it on the pedal. What this attachment point appears to do is spend a lot of pedal travel moving the rod up (or down) and not so much in (out) which is why I think it takes so long to activate the clutch. These pedals were supplied by Keisler as part of the kit, so I don't know if that attachment point was drilled by them or by the person that installed it in the car.

The question here is do I need to move the connection point? If so, I then have to figure out how to either drill into that post to be able to attach the rod with the pedal in the car or figure out how to get the pedal out.

Thanks!

 

[yellow rose]

If you go to the 4 speed forum, you will see a similar thread by Dr Charles. He is having similar issues.

Read through that. It might help.

And yes, you should have some adjustability in the system, and it shouldn't grind going into reverse.

 

[dukeboy440]

Back when I had my 73 Duster restored I had the drive train swapped and had a Keisler perfect fit kit (TKO 500) put in it. This came with a hydraulic clutch setup. I never liked the clutch pedal in this car. The way it is setup, i have to push the pedal as far as it will go and it still will grind going into reverse sometimes. Plus I am short so I have to sit a little closer to the wheel than I would like to get the clutch all the way in. The guy that did the work said the pedal wasn't adjustable because it was hydraulic. I didn't really believe him, but only now started looking into it.

Since Keisler is out of business I can't ask them any questions. I also don't have any of the installation instructions since I didn't do any of the work. I looked on Silver Sport Transmission's website, since they bought the perfect fit kit rights, and their instructions say to install the pedal connection, in most cases, to the stock location. My pedal is attached (see below) near the middle of the pedal shaft when the service manual says the mechanical clutch rod would have connected to the topmost post above it on the pedal. What this attachment point appears to do is spend a lot of pedal travel moving the rod up (or down) and not so much in (out) which is why I think it takes so long to activate the clutch. These pedals were supplied by Keisler as part of the kit, so I don't know if that attachment point was drilled by them or by the person that installed it in the car.

The question here is do I need to move the connection point? If so, I then have to figure out how to either drill into that post to be able to attach the rod with the pedal in the car or figure out how to get the pedal out.

Thanks! View attachment 1714994717

Call Silver sports. They bought keislers product lines and are selling the same stuff under the new name

 

[RedFish]

In most OEM assemblies, A hydraulic clutch/slave setup is not adjustable. It sort of self adjusts as the clutch wears ( really just the release point moving farther away ). After a certain point you can't get reverse ( or first gear depending on what gear box ) without some grinding. Nature of the beast as it were. I dont know why or how aftermarket would be any different.
Then again... The hex shaped section shown in your pic is/works as a turnbuckle. Maybe adjust the master stroke there? That would adjust the slave stroke also but... It can only travel the full length of its stroke.
It's much more likely that turnbuckle only adjusts the pedal height. Bottom line, If this was a factory build, the factory service tech would say, "you need a clutch".

 

[NukeBass]

It's been like this since first installed so I don't think it is the clutch. I messed with the turnbuckle a little, but pedal travel is limited by the brackets. I'll see if I can rig something to that top post without doing any cutting or drilling to see if that helps with cylinder rod alignment.

 

[dukeboy440]

You might also try bleeding the slave by hand. It's possible there's an air bubble

 

[rklein383]

I have had to remove a slave cylinder in the past and rotate it so the bleed was on the top, bleed it, and then reinstall.
Not sure why the factory (Nissan) did it that way.

 

[72bluNblu]

Putting the push rod down there on the pedal changes the pedal ratio. That's why the pedal has to hit the floor to move enough fluid.

I would relocate the push rod mounting point. You could take a look at 72BBswingers set up, he has a hydraulic clutch set up off the stock clutch pedal for his t56 conversion. The only issue is you might also have to relocate the clutch master cylinder.

Here it is...

 

[rklein383]

I am planning on putting a hydraulic clutch in my 71 Barracuda. I called Centerforce about it, asking about how much travel the throwout bearing needs, they said 1/2 inch. I lean towards keeping the master cylinder rod near the stock location not to affect the pedal ratio too much and moving the attachment point on the clutch fork to where you would get that amount of travel. Of course, you need to take into account the bore size of the master and slave cylinder. If they are the same, the travel will be the same on either side.

 

[DrCharles]

Putting the push rod down there on the pedal changes the pedal ratio. That's why the pedal has to hit the floor to move enough fluid.

First part is correct. Second is not. Moving the push rod closer to the pedal decreases the ratio (nominally 6:1) which moves more fluid from the master for a given movement of the pedal! It also increases the effort required due to the same reduction in leverage.

As YR mentioned, I had a similar problem with a homebrew setup in another thread in the 4-speed forum. I also moved the slave attachment point closer to the fork on the pivot (easier to do than removing the pedal and redrilling/welding the master attachment point).

I called Centerforce about it, asking about how much travel the throwout bearing needs, they said 1/2 inch.

That's a useful data point, although that probably includes the free play as well. Look at a fork and you'll see the ratio of the fork is around 2.5:1 (hole to pivot to throwout). That implies you need over an inch of travel at the fork hole, which I also found by experiment.

I lean towards keeping the master cylinder rod near the stock location not to affect the pedal ratio too much and moving the attachment point on the clutch fork to where you would get that amount of travel. Of course, you need to take into account the bore size of the master and slave cylinder. If they are the same, the travel will be the same on either side.

Good advice, since you don't want to over-stroke your master cylinder. Everything factors in to the overall ratio between the clutch disc and your foot. Pedal ratio, MC bore, slave bore, fork ratio and PP finger ratio. And you have to pick components so that the travel of both the master or slave is within ratings.
Where I went wrong is not knowing the effective piston diameter of my slave cylinder (a pull cylinder will have less than the bore size since the rod takes up part of that area). Anyhow, relocating the fork hole fixed it.

 

[72bluNblu]

First part is correct. Second is not. Moving the push rod closer to the pedal decreases the ratio (nominally 6:1) which moves more fluid from the master for a given movement of the pedal! It also increases the effort required due to the same reduction in leverage.

I think you're calculating your pedal ratio from the original geometry, which has no meaning at all for a hydraulic clutch. No Z-bar, no clutch rod, and in most cases no clutch fork or pivot. The only thing that matters for the hydraulic clutch with regard to the pedal is the amount of travel for the push rod, and the location of the pushrod on the length of the pedal. The location of the push rod along the length of the pedal determines you mechanical advantage (totally separate from any hydraulic advantage present), and the distance the pedal travels from rest to stop at the push rod mounting location location determines the travel unless it's longer than the stroke on the master cylinder (which would not be good).

The problem is that when you're using the stock pedals you've already had most of the geometry laid out for you. The pedal height has been set. The length of the clutch pedal is set. The travel distance to the floor/firewall is set. You can move the push rod mounting location, but you have to watch the amount of travel, the amount of arc, and your mechanical advantage closely. And since moving that around also changes the mounting of the master cylinder, you have to make sure you can mount the master cylinder at that location on the firewall.

You're far better off making adjustments by changing the bore and stroke of the master cylinder. Personally I would move the push rod mount back up so that it's inline with the stock mounting point for the clutch rod and go from there (notice that on 72BBswingers set up there is no overcenter spring/clutch rod arm). I know that the 7/8" wilwood master cylinder works well with the T56 conversions using the Viper T56 slave cylinder, but I don't know what you've got in there with a TKO conversion. You may find that the master cylinder you have works fine with the relocated push rod, or you may need to change it in order to match the travel needed for the master cylinder up with the travel available from the pedal.

 

[DrCharles]

I think you're calculating your pedal ratio from the original geometry, which has no meaning at all for a hydraulic clutch. No Z-bar, no clutch rod, and in most cases no clutch fork or pivot.

It hardly has "no meaning at all". As I already said, the overall ratio from the pedal to the clutch disc separation is determined by multiplying the ratio set by each piece of the system. The Z-bar just introduces another ratio since it probably isn't exactly 1:1.

If you are brave enough to use a hydraulic throwout bearing (really fun to tinker with inside the bellhousing, and requiring removal of the trans if there are any problems) then obviously there is no rod or fork. Still doesn't change the fact that there is a partially mechanical, partially hydraulic linkage between your foot and the clutch fingers. You move your foot six inches, the pressure plate moves .060".

The other advantage to using the original clutch pedal actuating location is that it provides just about 1" of stroke to the master cylinder, which is within the operating range of most readily available ones (1.2-1.4"). I found it a lot easier to grind one hole in the fork than keep buying $75 master cylinders and changing them... but to each their own.

 

[LJ67barracuda340]

the Keisler hyd throwout bearing is spring loaded and rides on the fingers all the time. it should be preloaded to 1/8 to 3/16 from bottoming. you might be running out of stroke. I have one of these in my 67