1985 C4 4+3 will not shift
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Joined: Apr 2006
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1985 C4 4+3 will not shift
Hello all,
I have a 1985 C4 with a 4+3 that will no longer shift gears with the engine running. The clutch will not release fully so to get from reverse to first or vice versa I have to shut the engine off, shift gears and then turn the engine back on. Shifting the other gears while driving is just like driving clutchless, even when using the clutch.
The car sat for a few months and then this problem appeared.
I have not had to add fluid often (I think I have added maybe 1/4 or less of the volume of the resevoir over the last 3 years).
I verified that the travel at the slave cylinder is around .7".
I removed the slave cylinder and the pedal feels rock hard when the slave piston is at the end of its travel.
The fluid was brownish, so I bled the system with new fluid just in case but it feels exactly the same.
It does feel as if the clutch is engaging a bit higher in its travel than it did before.
I do not feel any vibration in the clutch pedal so I think the throwout bearing is good.
There is a bit of slop in the master cylinder to pedal joint, leading to perhaps .25" of lost motion at the pedal.
The car has about 55k miles.
Does anyone have any suggestions as to what the problem might be?
Thank you very much for your help.
I have a 1985 C4 with a 4+3 that will no longer shift gears with the engine running. The clutch will not release fully so to get from reverse to first or vice versa I have to shut the engine off, shift gears and then turn the engine back on. Shifting the other gears while driving is just like driving clutchless, even when using the clutch.
The car sat for a few months and then this problem appeared.
I have not had to add fluid often (I think I have added maybe 1/4 or less of the volume of the resevoir over the last 3 years).
I verified that the travel at the slave cylinder is around .7".
I removed the slave cylinder and the pedal feels rock hard when the slave piston is at the end of its travel.
The fluid was brownish, so I bled the system with new fluid just in case but it feels exactly the same.
It does feel as if the clutch is engaging a bit higher in its travel than it did before.
I do not feel any vibration in the clutch pedal so I think the throwout bearing is good.
There is a bit of slop in the master cylinder to pedal joint, leading to perhaps .25" of lost motion at the pedal.
The car has about 55k miles.
Does anyone have any suggestions as to what the problem might be?
Thank you very much for your help.
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Joined: Jul 2006
Posts: 25
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I have experienced similar problems with my 85. I suspect you simply haven't gotten your clutch bled adequately. I had to bleed my system several times before it finally started working properly.
There are numerous posts about how to do this. I would recommend you read through them then give it another try.
There are numerous posts about how to do this. I would recommend you read through them then give it another try.
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Joined: Apr 2006
Posts: 91
Likes: 117
Thank you for the replies.
I did the bleeding by removing the slave and holding it vertically with the bleeder up as well as by pushing the slave piston in. I think I did a reasonable job, although from the amount of trouble that people have with these, I can believe that it might not be 100%.
With that said, the fact that it stopped working suggests to me that I should replace the 26 year old master cylinder and slave cylinder.
I found a bunch of different options (Dorman, Sachs, ACDelco, Brute Power, Bendix, Exedy) on RockAuto including ACDelco, which I am leaning towards. Does anyone have an opinion as to the best choice of brand including NAPA, Kragen, etc?
Also, does anyone have a PN or source for the hose between the cylinders?
I did the bleeding by removing the slave and holding it vertically with the bleeder up as well as by pushing the slave piston in. I think I did a reasonable job, although from the amount of trouble that people have with these, I can believe that it might not be 100%.
With that said, the fact that it stopped working suggests to me that I should replace the 26 year old master cylinder and slave cylinder.
I found a bunch of different options (Dorman, Sachs, ACDelco, Brute Power, Bendix, Exedy) on RockAuto including ACDelco, which I am leaning towards. Does anyone have an opinion as to the best choice of brand including NAPA, Kragen, etc?
Also, does anyone have a PN or source for the hose between the cylinders?
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
IIRC< Eckler's used to carry the hose assembly, but any competent hydraulic equipment shop can fab up a hose for you. Take the old line to them and they can match up the ends and build a hose. The OEM assembly is part hard line and part flex hose and if the metal part is in good shape, it's easy to build a short flex line.
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Joined: Apr 2006
Posts: 91
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Update:
I got a new master, slave and hose assembly from Ecklers. I installed all three together and bled the system a bunch of times until it felt totally rock hard. The old master cylinder had a lot of play in the input rod (~1/8" at least axially) and the new one definitely feels a lot tighter. However, the transmission behavior was exactly the same!
I then removed the master cylinder and installed it without the firewall spacer to get more travel. This might have made a tiny bit of difference but not that much.
I am thinking that something must be wrong with either the pressure plate (like the fingers are too weak from aged and use) or the throwout bearing. I see that clutch kits from Summit and others are around $200-$250.
Does anyone a recommendation on a stock type clutch replacement kit? Also, what diameter is the stock clutch?
I got a new master, slave and hose assembly from Ecklers. I installed all three together and bled the system a bunch of times until it felt totally rock hard. The old master cylinder had a lot of play in the input rod (~1/8" at least axially) and the new one definitely feels a lot tighter. However, the transmission behavior was exactly the same!
I then removed the master cylinder and installed it without the firewall spacer to get more travel. This might have made a tiny bit of difference but not that much.
I am thinking that something must be wrong with either the pressure plate (like the fingers are too weak from aged and use) or the throwout bearing. I see that clutch kits from Summit and others are around $200-$250.
Does anyone a recommendation on a stock type clutch replacement kit? Also, what diameter is the stock clutch?
Team Owner
Joined: Jan 2003
Posts: 20,315
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From: Summerland B.C. Canada
Stock clutch is 10 3/4". I bought Luk off Ebay, seemed like a quality product.
Before you decide to do the clutch, pull the fork boot back and see if the fork is positioned properly on ball stud.
Also, have someone push the clutch while you watch the fork action.
Before you decide to do the clutch, pull the fork boot back and see if the fork is positioned properly on ball stud.
Also, have someone push the clutch while you watch the fork action.
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Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
It's possible that the ball stud has been bent or is broken. Same with the clutch fork. It's also possible that the end of the fork that holds the throwout bearing is bent/broken.
Having worn or broken fingers or springs in the pressure plate can also be a problem.
When you drive the car, is there any indication of clutch slippage? While driving at a slow speed (say 30 MPH) and the trans in 4th gear, accelerate using medium throttle and see if RPM rises quickly. That would indicate a worn clutch disc.
Luk is a good clutch package if you need to replace the clutch assembly. Make sure the flywheel is in good condition and it's a good idea to have it machined as part of a clutch replacement job. If the kit doesn't come with a new pilot bearing, make sure one is installed.
Having worn or broken fingers or springs in the pressure plate can also be a problem.
When you drive the car, is there any indication of clutch slippage? While driving at a slow speed (say 30 MPH) and the trans in 4th gear, accelerate using medium throttle and see if RPM rises quickly. That would indicate a worn clutch disc.
Luk is a good clutch package if you need to replace the clutch assembly. Make sure the flywheel is in good condition and it's a good idea to have it machined as part of a clutch replacement job. If the kit doesn't come with a new pilot bearing, make sure one is installed.
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Joined: Apr 2006
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I watched the motion of the fork under the slave boot while someone was pushing the clutch and it appears correct to me. The slave rod travels at least .5" (probably more like .7" but I didn't measure it), the motion is smooth and everything feels tight during the motion.
Does it matter if the pointy end of the slave push rod is in the slave cylinder or the depression in the fork? The pointy end on mine was in the slave cylinder.
When the clutch is not pushed, I cannot push the fork at all towards the rear of the car (I guess my fingers aren't as strong as 1500 psi hydraulics
). Under the same condition there is a little bit of movement towards the front of the car possible under low load and then the fork springs back into position when released. Is this correct?
The last time I drove the car (before it went on jackstands), the clutch was holding fine, no problem at all.
I do remember that the car made more mechanical noise than I expected with the clutch pedal pressed in while sitting at a light for instance. Is this a sign of a worn out throwout bearing? I never felt much vibration or anything through the clutch pedal.
Does it matter if the pointy end of the slave push rod is in the slave cylinder or the depression in the fork? The pointy end on mine was in the slave cylinder.
When the clutch is not pushed, I cannot push the fork at all towards the rear of the car (I guess my fingers aren't as strong as 1500 psi hydraulics
). Under the same condition there is a little bit of movement towards the front of the car possible under low load and then the fork springs back into position when released. Is this correct?The last time I drove the car (before it went on jackstands), the clutch was holding fine, no problem at all.
I do remember that the car made more mechanical noise than I expected with the clutch pedal pressed in while sitting at a light for instance. Is this a sign of a worn out throwout bearing? I never felt much vibration or anything through the clutch pedal.
