85 2.8l 4Spd can't shift gears while running. (Page 1/5)
McCool JUN 04, 08:53 PM
Hey guys,

As the title says, my four speed won't shift (while running). Depressing the clutch pedal seems to not quite disengage the clutch from the flywheel. Example being, If you put the car in first gear, depress the clutch pedal all the way and start the car, the car lurches forward. if you keep the pedal depressed the car will still start, but the car will move forward slowly like the clutch is slipping, if you take it out of gear, you would be unable to put into any gear without turning the car off. depressing the clutch moves the slave cylinder piston, but I'm not sure the exact length of travel.

I figured I would try the cheapest and easiest fix before I went crazy. The clutch fluid level was fine but I bled the system and some filthy looking fluid came out, but seemingly no air. The new fluid wasn't enough to fix the problem. My slave cylinder is not that old in terms of KMs, but maybe the fluid was contaminated and rusted it out from the inside or something?

Anyways, is there a way to isolate whether its the slave or master cylinder thats failing, or is my best bet just to change the slave cylinder and if that doesn't work, change out the master?

As well, the Fiero shop service manual says that this problem is likely within the transmission itself (Fork and bearing problem, loose clutch bolts, clutch binding on input shaft, etc), this seems unlikely but is there a way to rule it out before I change out the clutch system?

EDIT FOR THOSE HAVING THE SAME PROBLEM:

In the end, the problem was in the clutch housing, a torsion spring broke loose and prevented the clutch from disengaging.

If someone is reading this thread because they are having the same problem I did, here's what I recommend you do.

1) verify that there is no air in the clutch line. A good way to check is it to take the rod out of the slave cylinder and let the piston in the slave be pushed all the way till it hits the snap ring that is retaining it. Get into the car, get your head down to where the pedals are, look at the banjo rod for the master cylinder and LIGHTLY push the clutch pedal in. if there is air in the system, the banjo rod will have a bit of travel and will feel bouncy (this is the air being compressed in the lines). If the putting pressure on the pedal does not move the banjo rod at all its because you are trying to push the slave piston through the retaining ring and you most likely don't have air in the system. While you are under there, inspect the banjo, make sure that the flat part of the banjo is facing the ground, that the banjo rod is not bent, and that there are no leaks from the master cylinder traveling down the banjo rod or dripping behind the carpeting.

1)b) if you have air in the system, there are special bleeding techniques required to properly bleed the system. V-8 Archie has a good method. I vacuum bled my system and it worked great but apparently other people have had problems with that before, so do what you are comfortable with.

2) Check the amount of travel on both the master and slave cylinder... from what I can gather, the master and slave cylinder bore diameters are the same. So when the master moves a certain amount, the slave should move the same amount. The maximum travel you will get from the master is around 1.25". No one can seem to tell me exactly how much travel you need on the slave to disengage the clutch, but consensus is just under 1". measure the travel on both the master and the slave cylinder. Make a mark on the banjo rod and the slave rod, depress the clutch (since I was working alone, I depressed the clutch and wedged a screwdriver between the clutch pedal and a flare on the steering column to hold it down) and measure the travel

3) If you aren't getting around 1" of travel of the banjo rod, make sure your clutch pedal isn't bent. Mine was good but from what everyone has been saying, if your clutch pedal isn't sitting over 1" higher than your brake pedal, then it is bent. Also check to see if you have an aluminum pedal or a steel one (put a magnet to it, if it sticks...it's steel) as the aluminum ones were prone to bending.

3) b) If you are getting 1" or more at the master but less than that at the slave, you need to remove the slave from its mounting bracket and measure it with out it being connected to the clutch arm as a block in the transmission might cause this problem. Once you have the slave removed from its mount, push the slave rod as far as it can go into the slave cylinder and get a helper to push the clutch pedal down. Measure the travel while pushing the slave rod firmly into the slave cylinder. If you are getting around 1" than the hydraulic portion of your clutch system is likely working fine. If you do not have 1" of travel, you have a faulty part within your hydraulic system, probably the slave cylinder (Use Rodney Dickman replacement they are cheaper and better than what you will get at a parts store).

4) If the movement of the master and slave is good then inspect clutch arm for bends or breaks, this apparently is an issue and will cause the problems I described above (this however was not my problem so I'm not 100% sure what you should be looking for). Removing the clutch arm to inspect is probably best, but mine was seized on so hard that I didn't want to risk bending the clutch fork trying to pry it off. It was easier to remove the heat shielding and stick my phone down there and take a good video of the arm so I get a good look at it from all sides.

5) If all this testing hasn't yielded a problem, then I'd bet you have a problem with the clutch assembly in the transmission.

[This message has been edited by McCool (edited 07-08-2019).]

Patrick JUN 04, 09:48 PM

There are about a billion threads here on this very issue.

If the slave is not moving at least an inch before the clutch pedal hits the floor, then you most likely still have air in the system... or your pedal (and/or banjo) is bent.
CSM842M4 JUN 04, 10:20 PM
With my wife's '84 2.5 4-speed, we have encountered a recurring need to bleed the clutch (caused by a leaking master cylinder) and loose slave mounting hardware. By the way, the clutch does NOT like to be bled the same way the brakes are bled. You or your helper will need to crack the bleeder, THEN press the clutch pedal to the floor,THEN close the bleeder. Resist the urge to "pump" the pedal or to pressurize the system before cracking the bleeder. Hope this helps.
McCool JUN 05, 12:07 AM

quote
Originally posted by Patrick:

If the slave is not moving at least an inch before the clutch pedal hits the floor, then you most likely still have air in the system... or your pedal (and/or banjo) is bent.



Thanks Patrick, when I am at the garage next I'll confirm the piston travel to be around 1 inch. I'll take a peek at the banjo bolt and the pedal as well.

I read in another post that someone having the same issue ended up having the bolts on the flywheel come out... so hopefully its something easier than that because I'm not sure I'm willing to drop the cradle at this moment.


quote
Originally posted by CSM842M4:

By the way, the clutch does NOT like to be bled the same way the brakes are bled. You or your helper will need to crack the bleeder, THEN press the clutch pedal to the floor,THEN close the bleeder. Resist the urge to "pump" the pedal or to pressurize the system before cracking the bleeder. Hope this helps.



Thanks for the tip, but I vacuum bled the system, it was much easier aside from the master cylinder reservoir being capable of holding no more than a half a milliliter of DOT 3.
olejoedad JUN 05, 06:04 AM
V-8 Archie has a write up on his website detailing a sure fire way to bleed all of the air out of the slave cylinder.
Bubbles may be trapped in the area near the pushrod, his method ensures they are removed.
Check it out, it works.
fierofool JUN 05, 08:28 AM
If you're vacuum bleeding or conventional bleeding, like olejoedad said, bubbles can be trapped at the pushrod end of the slave. The left front of the car needs to be lifted just enough that the wheel starts to come off the ground. Do your bleeding but rap on the side of the slave a few times in the process to make those trapped air bubbles move up to the bleeder end.

Five things to check:
1. Does the clutch pedal sit about 1 inch higher than the brake pedal?
2. Poke your finger all the way up into the hole where the pushrod goes into the back of the slave. Fluid leaks aren't always visible in this area.
3. Is the curl on the banjo rod turned upward?
4. Slip the boot off the end of the slave and check for fluid.
5. While someone operates the clutch, observe the slave cylinder bracket. If it moves it's cracked or loose. Breaking is a common problem with the 4-speed bracket.
McCool JUN 05, 11:04 PM

quote
Originally posted by fierofool:

If you're vacuum bleeding or conventional bleeding, like olejoedad said, bubbles can be trapped at the pushrod end of the slave. The left front of the car needs to be lifted just enough that the wheel starts to come off the ground. Do your bleeding but rap on the side of the slave a few times in the process to make those trapped air bubbles move up to the bleeder end.

Five things to check:
1. Does the clutch pedal sit about 1 inch higher than the brake pedal?
2. Poke your finger all the way up into the hole where the pushrod goes into the back of the slave. Fluid leaks aren't always visible in this area.
3. Is the curl on the banjo rod turned upward?
4. Slip the boot off the end of the slave and check for fluid.
5. While someone operates the clutch, observe the slave cylinder bracket. If it moves it's cracked or loose. Breaking is a common problem with the 4-speed bracket.



The clutch pedal sits higher than the brake, the slave cylinder does not appear to be leaking, and the cylinder bracket does not appear to be broken. However I don't know what you mean by "banjo rod turned upward".

I bleed the system v-8 archies way and tested the slave cylinder travel and only got somewhere in the area of 3/4" of travel. So I might be looking at changing the slave cylinder first and moving on from there.
Patrick JUN 05, 11:19 PM

quote
Originally posted by McCool:

I don't know what you mean by "banjo rod turned upward".



The banjo is not symmetrical. The "loop" goes up.

If you decide to get a slave, make sure to get Rodney's.
fierofool JUN 06, 11:21 AM
Where it attaches to the pedal it should be oriented like this:
McCool JUN 07, 06:53 PM
Okay, so the banjo of the master cylinder is up. And does not appear to be bent.

I replaced the slave cylinder and bled the system the archie way and I'm still only getting about 3/4" if movement at the slave piston,the pedal feels very firm and I would be surprised if there was more air in the system.

From what I can tell, the clutch pedal is not bent, it does sit higher than the brake pedal and the U shaped bracket that attaches to the banjo seems square and secure. As well, I have a steel clutch pedal, not an aluminum one. I did notice that the banjo from the master cylinder is worn in such a way that makes me feel it used to be pushed further, but maybe that has more to do with the grommet being old and worn down... I'm not sure how to verify whether or not the master cylinder rod is traveling enough.

I'm not sure what to do now.