Clutch Fork Spring

[Nomis]

I replaced my clutch master and slave cylinder today and I noticed something odd. When I have the OEM spring that goes between the slave cylinder and the fork installed - it depresses the slave rod all the way which I would think would be the intent. The problem is, at that point my clutch pedal is mushy and goes straight to the floor without releasing the clutch and pumping it repeatedly builds no pressure at that point. However, if I remove the spring, the clutch works fine. It actuates the clutch fork and releases the clutch perfectly. There are no leaks at either the master or slave and I bled the system repeatedly to ensure no air was in the line.
I drove around town for 30 minutes without the spring installed and it worked fine. The part number for the OEM spring I have installed is 90506-16475. I am using a slave from NAPA and a Beck Arnley master. I should also note that the previous slave had no spring on it either and appeared to be the original Toyota/Aisan judging by the anodized green piston. It was working fine up until it puked out all my clutch fluid a few days ago. What is the deal with this spring?

 

[Nomis]

If I run it without the return spring on the slave - will it eat up the throwout bearing? Any ideas?

 

[65swb45]

The main purpose of the return spring is to keep the throwout bearing away from the pressure plate when the clutch is not being used, so yes, IMO you should have one. That said, I know that the 86-87 wagons didn't run one.

Do I like that system. NO! Have I retrofitted 86-87 wagons to slave/fork combos that utilize a spring. YES!

Your slave cylinder pushrod has a nut on the end of it intended to be adjusted out to take up the gap between the throwout bearing and pressure plate. Various manuals list the spec for this.

Adjusting the pushrod length will solve your problem.

Best

Mark A.

 

[Bodean]

Hey Mark, Mine has never had a spring. What's up with that? It's a 78.

later,

 

[Cruiserdrew]

The main purpose of the return spring is to keep the throwout bearing away from the pressure plate when the clutch is not being used, so yes, IMO you should have one. That said, I know that the 86-87 wagons didn't run one.

Do I like that system. NO! Have I retrofitted 86-87 wagons to slave/fork combos that utilize a spring. YES!

Your slave cylinder pushrod has a nut on the end of it intended to be adjusted out to take up the gap between the throwout bearing and pressure plate. Various manuals list the spec for this.

Adjusting the pushrod length will solve your problem.

Best

Mark A.

And weirdly the slave push rod in the 85-87s is non-adjustable. The earlier slave is a much better unit and can be adjusted for perfect engagement. I think the spring is useful and spares excess wear on the throwout face and the clutch fingers.

 

[Nomis]

Adjusting the pushrod length will solve your problem.

I must be doing something wrong then as I adjusted the rod length and it still will not function properly. As soon as I connect the spring - the rod bottoms out in the cylinder. From that point forward, the slave will only actuate the fork up to the point where it starts to engage the pressure plate and then nothing. Remove the spring and it works fine. I re-bled it last night and nothing but fluid comes out. Is the slave supposed to retain any residual pressure or is it normal for the rod/plunger to bottom out in the slave due to the spring tension?

 

[Mr. Toad]

I must be doing something wrong then as I adjusted the rod length and it still will not function properly. As soon as I connect the spring - the rod bottoms out in the cylinder. From that point forward, the slave will only actuate the fork up to the point where it starts to engage the pressure plate and then nothing. Remove the spring and it works fine. I re-bled it last night and nothing but fluid comes out. Is the slave supposed to retain any residual pressure or is it normal for the rod/plunger to bottom out in the slave due to the spring tension?

Did you try to adjust the nut so that there is no spring pressure (delivered from the fork and down the pushrod) on the adjusting nut when the clutch is released?

 

[dbarrett]

I had/have the same problem with my 72 and a transplanted 77 2f and 4 speed clutch. The clutch works fine without the spring. When I put the spring on, everything goes mushy. Takes a good 3-4 pumps to get the clutch to engage. Tried adjusting the nut on the push rod and gave up. Been running with no spring for 5 years now. Are the push rods different lengths from 72 to 77? I just might have the old 72 rod in there and that is where the adjustment problem is???

 

[Nomis]

Did you try to adjust the nut so that there is no spring pressure (delivered from the fork and down the pushrod) on the adjusting nut when the clutch is released?

Yes, but as soon as the spring is connected - it forces the rod back into the bore. Is the spring supposed to bottom out the rod - or is there supposed to be residual pressure in the slave that keeps it from bottoming out?

I had/have the same problem with my 72 and a transplanted 77 2f and 4 speed clutch. The clutch works fine without the spring. When I put the spring on, everything goes mushy. Takes a good 3-4 pumps to get the clutch to engage. Tried adjusting the nut on the push rod and gave up. Been running with no spring for 5 years now. Are the push rods different lengths from 72 to 77? I just might have the old 72 rod in there and that is where the adjustment problem is???

Bingo - at least I am not the only one (although, my pedal will not get firm regardless of the number of pumps). Also, the pushrod on the new slave is the same length as my old unit.
If you have been running with no spring for 5 years - that makes me feel somewhat okay about leaving it off. I wonder how many other folks are running without the spring. A small voice inside me is telling me to set it up correctly with the spring - but that can be squelched with

If you guys see me start a thread on throwout bearings in the near future - try not to beat me up too much.

 

[dbarrett]

Let me clarify, 5 years of driving with no spring but not my daily driver. Probably drive it 2-3 days out of a week. That probably makes a big difference on the wear and tear on the TO bearing. I am going to go through my bucket of parts to see if I have a rod or two that are different lengths and give them a try. I'll let you know.

 

[Nomis]

Let me clarify, 5 years of driving with no spring but not my daily driver. Probably drive it 2-3 days out of a week.

I take mine out once a week if I'm lucky - so it should last 15 years at that rate

 

[Mr. Toad]

Yes, but as soon as the spring is connected - it forces the rod back into the bore. Is the spring supposed to bottom out the rod - or is there supposed to be residual pressure in the slave that keeps it from bottoming out?

Here's what I think is going on:

Your clutch is WAY out of adjustment.

When the spring is unattached, the throwout bearing pushes the fork back (Just like disc run-out pushes brake pads out)

The fork stops when once the TO bearing is no longer in contact. This is the starting position with the spring unattached.

With the spring unattached, pushing the clutch pedal moves the fork from the starting position, and the movement is enough to operate the clutch.

When you attach the spring, it pulls the fork to the limit -- i.e. until the slave rod is bottomed.

When you push the clutch pedal with the spring attached, the slave rod moves the same amount as before, but it's no longer anywhere near the activation point of the clutch.

Pumping does nothing because there is no residual pressure and no residual valve in the system. As soon as you let off the pedal, the spring delivers the rod back to the bottoming point.

What to do:

1. With spring off, work the clutch. Make sure it's working.

2. Let off the clutch pedal.

3. Mark the distance between the slave cylinder and the clutch fork.

4. Adjust the slave rod nut so that (a) the rod is bottomed in the slave, and (b) the distance between the slave cylinder and the clutch fork is the same as you measured before (maybe a quarter or half cm less even)

5. Reattach the spring.

6. Drive.

 

[Fast Eddy]

When you push the clutch pedal with the spring attached, the slave rod moves the same amount as before, but it's no longer anywhere near the activation point of the clutch.

This makes a lot of sense.

 

[Nomis]

This makes a lot of sense.

Agreed.
I will follow this process as soon as I get back to the house and report back. There is one last piece of info that I think would help out - what is the length of the stock push rod itself? It is possible the pushrod I am using is too short for this application.

I can measure mine and report back. I do know it is the same length as the old one - but it could have been the wrong one as well.

 

[dbarrett]

this might help

Attached is a pic of possible push rod combinations and lengths. The rods all appear to be the same length but the difference between the first rod (might have come from my 77 4 speed???) and the second (might have come from a 72 3 speed) is the adjustment nut. The first rod's nut allows for lots of adjustment due to the fact that the nut does not have a cap and allows the shaft to move up and down along the threads. The second rod has a nut that is capped and will bottom out thus stopping adjustment at a set point. The third rod is similiar to the first rod but appears to be a tad bit longer. I am running the bright shiny third rod now and it works just fine without the spring. The big question, is the third rod correct for a 77 clutch? If it is, then I can use Toads points for adjustment. The last important question, which spring is correct?? I found two in my bag-o-clutch parts. My rig came in pieces so I am not sure which spring is which or where they came from. Thanks for any guidence you guys can give.

 

[Nomis]

Attached is a pic of possible push rod combinations and lengths. The rods all appear to be the same length but the difference between the first rod (might have come from my 77 4 speed???) and the second (might have come from a 72 3 speed) is the adjustment nut. The first rod's nut allows for lots of adjustment due to the fact that the nut does not have a cap and allows the shaft to move up and down along the threads. The second rod has a nut that is capped and will bottom out thus stopping adjustment at a set point. The third rod is similiar to the first rod but appears to be a tad bit longer. I am running the bright shiny third rod now and it works just fine without the spring. The big question, is the third rod correct for a 77 clutch? If it is, then I can use Toads points for adjustment. The last important question, which spring is correct?? I found two in my bag-o-clutch parts. My rig came in pieces so I am not sure which spring is which or where they came from. Thanks for any guidence you guys can give.

The spring on the left is the clutch pedal return spring - it installs on the clutch pedal itself at the top of the pedal on the same pin that connects the master cylinder rod to the pedal - the other end of the spring connects to a tab under the dash.

The second spring on the right is the slave spring.

Thanks for your pics - my slave rod looks identical to the bottom one in your pic - ie the gold one.

 

[Nomis]

Okay, Mark A. , Mr. Toad, et al. were correct - it was out of adjustment. I adjusted the slave rod nut until it was almost fully out at the tip - had around 1/16" play between the pushrod and the fork. Then adjusted the master cylinder rod to pick up the pedal play. Now the clutch is working - WITH THE SPRING INSTALLED. I still need to take it out for a test drive but I'm sure it will be fine.

Thanks folks.

 

[rloaderro]

Same problem. The slave rod might not be long enough because even with the nut adjusted all the way to the end of the rod it's not the same distance as #3. I guess you can also adjust the pedal, but I'm not sure what I should be adjusting for. I'm guessing it's the bolt #94120, but moving it one way or the other doesn't seem to affect the pedal position. What should I be aiming for?

What to do:

1. With spring off, work the clutch. Make sure it's working.

2. Let off the clutch pedal.

3. Mark the distance between the slave cylinder and the clutch fork.

4. Adjust the slave rod nut so that (a) the rod is bottomed in the slave, and (b) the distance between the slave cylinder and the clutch fork is the same as you measured before (maybe a quarter or half cm less even)

5. Reattach the spring.

6. Drive.

 

[Nomis]

Same problem. The slave rod might not be long enough because even with the nut adjusted all the way to the end of the rod it's not the same distance as #3. I guess you can also adjust the pedal, but I'm not sure what I should be adjusting for. I'm guessing it's the bolt #94120, but moving it one way or the other doesn't seem to affect the pedal position. What should I be aiming for?

I would say pick up the correct slave rod first if the one you have is significantly shorter. IIRC, the diesel slave cylinders have a shorter rod - maybe that is what you have currently. Bring the rod pic and a measuring tape with you to the parts store to confirm. As for adjusting the pedal, you are correct the part #94120 in your diagram rotates out which gives you a longer throw on the rod and in turn pushes a higher volume of fluid out of the master to the slave. That said, there should be a little slack, around 1/8" IIRC - you don't want the master/slave under constant pressure.

 

[rloaderro]

Thanks for your reply. I haven't had luck adjusting the clutch - still pumping to get pressure. This is the odd thing though - last week pressure was great. Suddenly died down though to where I was pumping it - this was in a matter of minutes. Brought the truck to the previous owner who adjusted it (i'm assuming just moving the nut to the end of the rod) and pressure came back again. A few days later it was gone (where I am now). However, the level of the clutch liquid hasn't dropped and I don't see leakage anywhere. What would be the first step - bleed the system? What could be going wrong? I feel like switching to a longer rod might only be delaying the problem slightly if there is a bigger issue somewhere else.