I need some help! Clutch hydralics questions
10-30-2012, 11:54 PM
#91
Rennlist Member
Thread Starter
ok, its not the clutch system it is working well. its the arm , pushrod, and the entire assemblly of the T/O bearing. maybe the throwout bearing is bad because i had the 2nd man rev the engine while i watched. the flywheel looks true, but the arm attached to the push rod is moving all over the place. it goes crazy at 5000rpm almost exactly but is vibrating pretty bad up to that point where the worse vibration occurs.
Greg, the Hs would further not be an issue, because remember, its all done with the clutch pedal NOT pressed down, so even if the H's were out of aligmenet due to a pin falling out, when the clutch is compressed by the pressure plate, the INT plate is sandwiched between the flywheel and pressure plate. you should have thought of this. in otherwords, it would be impossible for the Hs to be a factor because the INT plate is leveled by being pressed on to the flywheel. if the H pins were strong enough to not allow contact on the flywheel side, the clutch would slip and it doesnt, plus you can see that under clamping there is plenty of room on front side of the Hs for wear. about .5mm
anyway, what would cause the lever arm to be so sloppy and move around so much under high rpm?
Mk
Greg, the Hs would further not be an issue, because remember, its all done with the clutch pedal NOT pressed down, so even if the H's were out of aligmenet due to a pin falling out, when the clutch is compressed by the pressure plate, the INT plate is sandwiched between the flywheel and pressure plate. you should have thought of this. in otherwords, it would be impossible for the Hs to be a factor because the INT plate is leveled by being pressed on to the flywheel. if the H pins were strong enough to not allow contact on the flywheel side, the clutch would slip and it doesnt, plus you can see that under clamping there is plenty of room on front side of the Hs for wear. about .5mm
anyway, what would cause the lever arm to be so sloppy and move around so much under high rpm?
Mk
10-31-2012, 12:52 AM
#93
Race Director
MK
I figured it out....the bushing at the top of the release arm is toast....I found one that was literally bent on the widow....it shouldn't move or wiggle like that..... my guess is the plastic bushing is long gone...
I figured it out....the bushing at the top of the release arm is toast....I found one that was literally bent on the widow....it shouldn't move or wiggle like that..... my guess is the plastic bushing is long gone...
10-31-2012, 01:19 AM
#94
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10-31-2012, 02:05 AM
#96
Rennlist Member
Thread Starter
oh yes, ill argue, becuase it was all wrong info. all three solutions would have been a waste of time and money. the slave was a good one as it was acting funny anyway, but the rest was wishful thinking. i dont wish! good shotgun solutions, but i wanted to know the cause................ and i found it. none of the things mentioned. the only one close , was Brian.
10-31-2012, 02:09 AM
#97
Rennlist Member
Thread Starter
I was going to start it and remove the lower bell housing, to see what is going on at speed. but i got enough information by running the car with my son gassing it to 5500rpm and me looking at what was moving around! the lever arm was moving around even as low as 1000rpm, but got crazy at 5000rpm. that was it!! so, then i pulled the bell housing and found the probem.. almost was ready to change out the master too!!! glad i didnt!
10-31-2012, 10:39 AM
#99
Race Car
Mark, that's not your problem, that's a symptom of the problem. Then the 2nd order symptom is the vibrations. I have had this exact thing happen. The TT bearings migrate to the wrong spots in the tube, usually the front bearing migrates back. This causes the shaft to not be properly supported towards the front and transmits vibration to the clutch pack and guide tube. This causes the guide tube bolts to get loose and back out. When that happens, the clutch starts to act funny. If the vibration is bad enough, no two fasteners in this world in the diameter that hold the guide tube will be enough to not back out, even with red loctite, BTDT. The guide tube is not designed to support the shaft, its purpose is to guide the movement of the release bearing.
After this, even if the TT bearings are replaced and put in their correct spots, the shaft may become bent and there will still be vibrations. It is also possible that your TT shaft is bent from the accident.
Use a coathanger to check how far the front TT bearing is from the end of the tube.
Dan
'91 928GT S/C
475hp/460lb.ft
After this, even if the TT bearings are replaced and put in their correct spots, the shaft may become bent and there will still be vibrations. It is also possible that your TT shaft is bent from the accident.
Use a coathanger to check how far the front TT bearing is from the end of the tube.
Dan
'91 928GT S/C
475hp/460lb.ft
10-31-2012, 01:12 PM
#100
Rennlist Member
Thread Starter
Mark, that's not your problem, that's a symptom of the problem. Then the 2nd order symptom is the vibrations. I have had this exact thing happen. The TT bearings migrate to the wrong spots in the tube, usually the front bearing migrates back. This causes the shaft to not be properly supported towards the front and transmits vibration to the clutch pack and guide tube. This causes the guide tube bolts to get loose and back out. When that happens, the clutch starts to act funny. If the vibration is bad enough, no two fasteners in this world in the diameter that hold the guide tube will be enough to not back out, even with red loctite, BTDT. The guide tube is not designed to support the shaft, its purpose is to guide the movement of the release bearing.
After this, even if the TT bearings are replaced and put in their correct spots, the shaft may become bent and there will still be vibrations. It is also possible that your TT shaft is bent from the accident.
Use a coathanger to check how far the front TT bearing is from the end of the tube.
Dan
'91 928GT S/C 475hp/460lb.ft
After this, even if the TT bearings are replaced and put in their correct spots, the shaft may become bent and there will still be vibrations. It is also possible that your TT shaft is bent from the accident.
Use a coathanger to check how far the front TT bearing is from the end of the tube.
Dan
'91 928GT S/C
475hp/460lb.ftnow, im trying to remember what was happening when i was looking and feeling the lever arm and push rod under running conditions. there was a little vibration at the lower rpm, up to 5000rpm that was noticable. however it almost seemed like the little vibration made big movement side to side on the lever arm. keep in mind, the lever arm and TO bearing are kept aligned by the sleeve. without it, the entire mechanism is REAL sloppy. even a little normal vibration will cause some wild movemnent on the lever arm and thus into the push rod. so that is what im hoping is the problem.
as a note, this was a new TT from 928 intl , and was one out of three that was the best of the bunch. the only think that now could be damage from the accident is the short shaft, or the flywheel mounted to the crank. it didnt look like there was any flyweel vibration at 6000rpm (as i have some BIG peek hole to see everything)
the bearing moving down the TT is a concern, and can you check with a hanger by sticking it in the hole in the TT and push bacward? how far should the bearing be located?
10-31-2012, 04:34 PM
#101
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UGGGGGGG i think you might be right. very good points!
now, im trying to remember what was happening when i was looking and feeling the lever arm and push rod under running conditions. there was a little vibration at the lower rpm, up to 5000rpm that was noticable. however it almost seemed like the little vibration made big movement side to side on the lever arm. keep in mind, the lever arm and TO bearing are kept aligned by the sleeve. without it, the entire mechanism is REAL sloppy. even a little normal vibration will cause some wild movemnent on the lever arm and thus into the push rod. so that is what im hoping is the problem.
as a note, this was a new TT from 928 intl , and was one out of three that was the best of the bunch. the only think that now could be damage from the accident is the short shaft, or the flywheel mounted to the crank. it didnt look like there was any flyweel vibration at 6000rpm (as i have some BIG peek hole to see everything)
the bearing moving down the TT is a concern, and can you check with a hanger by sticking it in the hole in the TT and push bacward? how far should the bearing be located?
now, im trying to remember what was happening when i was looking and feeling the lever arm and push rod under running conditions. there was a little vibration at the lower rpm, up to 5000rpm that was noticable. however it almost seemed like the little vibration made big movement side to side on the lever arm. keep in mind, the lever arm and TO bearing are kept aligned by the sleeve. without it, the entire mechanism is REAL sloppy. even a little normal vibration will cause some wild movemnent on the lever arm and thus into the push rod. so that is what im hoping is the problem.
as a note, this was a new TT from 928 intl , and was one out of three that was the best of the bunch. the only think that now could be damage from the accident is the short shaft, or the flywheel mounted to the crank. it didnt look like there was any flyweel vibration at 6000rpm (as i have some BIG peek hole to see everything)
the bearing moving down the TT is a concern, and can you check with a hanger by sticking it in the hole in the TT and push bacward? how far should the bearing be located?
https://rennlist.com/forums/928-foru...d-tools-3.html
10-31-2012, 06:58 PM
#102
Rennlist Member
Thread Starter
Took the car out for a comprehensive test drive. the clutch is good now. no pedal problems at all. all near redline shifts , even keeping the RPM at 5500rpm for a period of time, with no unusual vibrations.
if there is a vibration that caused the failure of the guide tube bolts, then it was slight. ill get under the car again and see what it feels like at 6000rpm again. you can just press your finger on the push rod and actually see the lever-fork arm too. so far, so good. everything feels as it should .
if there is a vibration that caused the failure of the guide tube bolts, then it was slight. ill get under the car again and see what it feels like at 6000rpm again. you can just press your finger on the push rod and actually see the lever-fork arm too. so far, so good. everything feels as it should .
10-31-2012, 11:02 PM
#103
Race Director
weird.....it had to be vibrations from the TT.....I doubt the clutch could cause that...
Sounds like a great time to upgrade to Consantines better TT bearings!!
Sounds like a great time to upgrade to Consantines better TT bearings!!
10-31-2012, 11:46 PM
#104
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You can easily drop the front of the TT and pound in another bearing and carrier with out removing all that much stuff. The extra bearing will center the driveshaft just fine. Mark A and I did this to the old very brown many years ago and althought the driveshaft has a noisey bearing somewhere inside everything else is just fine after untold hours of "autocross" driving 15-20 minite sessions as fast as humanly possible
11-01-2012, 02:29 AM
#105
Rennlist Member
Thread Starter
so far, ive run the engine up to 6000rpm many times and there are no unusual vibrations and the clutch is working perfectly now. There might be a problem with the T/O bearing as it seems a little old and dry. but as far as i know , the car feels and runs the same as it has since we put all the Holbert stuff in the new chassis back 3 years ago now.
You can easily drop the front of the TT and pound in another bearing and carrier with out removing all that much stuff. The extra bearing will center the driveshaft just fine. Mark A and I did this to the old very brown many years ago and althought the driveshaft has a noisey bearing somewhere inside everything else is just fine after untold hours of "autocross" driving 15-20 minite sessions as fast as humanly possible