New clutch will not grab
09-08-2018, 04:29 PM
#1
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New clutch will not grab
So, my buddies truck died at my house (1990 F150 5.0 M5OD) he had been noticing the clutch slipping for a while and it finally went out completely. It also had a terrible grinding coming from the clutch.
I laid under it and looked in at the slave cylinder while he released the clutch. Sure enough, the transmission shaft was not moving at all with the clutch fully out.
So... I pulled the transmission out and replaced the clutch and flywheel (old one was badly worn into)
I actually went with the 11" clutch this time and had to get new bolts for the pressure plate to flywheel blots. I torqued the flywheel to engine bolts at 70ish ft/lbs, but the pressure plate bolts only called for 30 ft/lbs. Seemed week, but whatever.
I put it back together and now the clutch still will not engage with the clutch fully out.
The pedal has plenty of pressure and the slave cylinder seems to be releasing just fine.
What am I overlooking?
I laid under it and looked in at the slave cylinder while he released the clutch. Sure enough, the transmission shaft was not moving at all with the clutch fully out.
So... I pulled the transmission out and replaced the clutch and flywheel (old one was badly worn into)
I actually went with the 11" clutch this time and had to get new bolts for the pressure plate to flywheel blots. I torqued the flywheel to engine bolts at 70ish ft/lbs, but the pressure plate bolts only called for 30 ft/lbs. Seemed week, but whatever.
I put it back together and now the clutch still will not engage with the clutch fully out.
The pedal has plenty of pressure and the slave cylinder seems to be releasing just fine.
What am I overlooking?
09-08-2018, 04:49 PM
#2
Senior Member
Are you sure the transmission isn't broken instead? Can you actually see the main shaft in to the transmission from underneath? Can you take a picture?
Since the system is hydraulic releasing the pressure should allow the clutch to engage. I don't know how pressure would get locked into the system but have you opened the bleed valve to be sure? Wild guess.
If you're sure that the clutch disc is correctly on the transmission input shaft splines then one possibility is that you installed the wrong parts and they are pressing on the pressure plate fingers. That's really all there is - flywheel to pressure plate to clutch disc to input shaft splines is the power path.
Since the system is hydraulic releasing the pressure should allow the clutch to engage. I don't know how pressure would get locked into the system but have you opened the bleed valve to be sure? Wild guess.
If you're sure that the clutch disc is correctly on the transmission input shaft splines then one possibility is that you installed the wrong parts and they are pressing on the pressure plate fingers. That's really all there is - flywheel to pressure plate to clutch disc to input shaft splines is the power path.
09-08-2018, 05:02 PM
#4
Senior Member
People do odd things some times. Are you sure you installed the new disc? Do you remember using the disc locating tool?
Do you remember that the edges of the pressure plate had a gap between them and the fly wheel that closed down when you installed the pressure plate bolts? The 30 ft-lb bolts. If the pressure plate edges were flat on the flywheel when you installed it that would be a sign that it was the wrong combination of parts. It's those bolts that actually apply the force of the pressure plate to squeeze the clutch disc and transmit power.
Not saying you don't know what you're doing just looking for confirmation that you had the right parts.
Here's something that you could probably do that will show if there's pressure on the clutch disc. Loosen each pressure plate bolt about 1 or 2 turns. The plate should lift off of the flywheel due to spring pressure. It will be safe because everything is located by the trans shaft. If you loosen those bolts and nothing happens then you don't have any pressure from the pressure plate. It will never work.
Do you remember that the edges of the pressure plate had a gap between them and the fly wheel that closed down when you installed the pressure plate bolts? The 30 ft-lb bolts. If the pressure plate edges were flat on the flywheel when you installed it that would be a sign that it was the wrong combination of parts. It's those bolts that actually apply the force of the pressure plate to squeeze the clutch disc and transmit power.
Not saying you don't know what you're doing just looking for confirmation that you had the right parts.
Here's something that you could probably do that will show if there's pressure on the clutch disc. Loosen each pressure plate bolt about 1 or 2 turns. The plate should lift off of the flywheel due to spring pressure. It will be safe because everything is located by the trans shaft. If you loosen those bolts and nothing happens then you don't have any pressure from the pressure plate. It will never work.