My PKlamp Experience
08-04-2009, 05:44 PM
#1
Under the Lift
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My PKlamp Experience
I bought a PorKen PKlamp from Roger and installed it before leaving for the OCIC. It was quiet easy to install on the front flexplate clamp. The production clamp is nicely plated and seems beefier than shown in the pictures of the pre-production unit. I made a mark in the shaft splines with white paint to help indicate if there was any movement. This is my first report on the clamp after about 4000 miles (odo currently 209,015 miles). I will follow up each time I check it, which is every 3-6 month (3000-6000 miles). Normally no matter how long or short the interval, I find 1-3mm of movement. This time - no movement.
I'll be editing this post to update my experience as each time I check the flexplate.
First report: 08/04/2009, 4,000 miles on PKlamp, 209,015 miles on odo - no movement. See Pic #1. Left it alone.
Update #1: 09/26/2009, 7,117 miles on PKlamp, 212,132 miles on odo - no movement. See Pic #2. Left it alone.
Update #2: 03/08/2010, 11,873 miles on PKlamp, 216,898 miles on odo - MAYBE 0.2 to 0.5mm movement. Left it alone. See Pic #3 - there is a slight break in the paint mark. No perceptible change in the flexplate. Not enough movement to do anything except check torque on PKlamp, and it was OK. This tiny movement compares favorably to 1-3mm of movement I would find whenever I checked the flexplate before installing the PKlamp. Note, as I comment in post #38 about this update, I did nothing special when I installed the PKlamp. If there is further movement I will remove it and the main clamp, degrease everything and install a new main bolt. Or I will do this in July 2010 when it is time for my annual crank endplay check during which I loosen the flexplate clamp anyway.
Update #3: 07/04/2010, 14,106 miles on PKlamp, 219,121 miles on odo - no additonal movement. See Pic #4. I removed the PKlamp and main clamp bolt to check crank endplay. It was unchanged at 0.008" (the same reading for years). Here's a description of how I check endplay: https://rennlist.com/forums/928-foru...pictorial.html The main clamp bolt sure did not feel like my usual 62 ft lbs when I loosened it. Anyway, I retorqued it and the PKlamp. Pic #5 - New paint mark after checking crank endplay and retorquing PKlamp and main clamp bolt.
Update #4: 02/14/2011, 9,250 miles since I reset the clamp, 228,371 on odo - no movement.
Update #5: 10/13/2011, 20,300 miles and 15 months since I reset the clamp when doing crank endplay check - 239,421 on odo - no movement. See Pic #6. I will be loosening the clamp since I need to repair the torque converter seal in my tranny. Time for my annual endplay check anyway. So, the interval willl start over. This 20K mile interval with no movement is long enough to make me believe the PKlamp is doing what Ken intended. In the past, before I added the PKlamp, it took no more that a few K miles to get 1-3mm of movement.
11/15/2011 - the tranny is out for leak repair. So, the next check will be a fresh start for the PKlamp.
Update #6: 06/30/2012, 3,457 miles since I reset the clamp after the tranny work, 242,878 miles on odo - no movement. Left it alone, of course.
I'll be editing this post to update my experience as each time I check the flexplate.
First report: 08/04/2009, 4,000 miles on PKlamp, 209,015 miles on odo - no movement. See Pic #1. Left it alone.
Update #1: 09/26/2009, 7,117 miles on PKlamp, 212,132 miles on odo - no movement. See Pic #2. Left it alone.
Update #2: 03/08/2010, 11,873 miles on PKlamp, 216,898 miles on odo - MAYBE 0.2 to 0.5mm movement. Left it alone. See Pic #3 - there is a slight break in the paint mark. No perceptible change in the flexplate. Not enough movement to do anything except check torque on PKlamp, and it was OK. This tiny movement compares favorably to 1-3mm of movement I would find whenever I checked the flexplate before installing the PKlamp. Note, as I comment in post #38 about this update, I did nothing special when I installed the PKlamp. If there is further movement I will remove it and the main clamp, degrease everything and install a new main bolt. Or I will do this in July 2010 when it is time for my annual crank endplay check during which I loosen the flexplate clamp anyway.
Update #3: 07/04/2010, 14,106 miles on PKlamp, 219,121 miles on odo - no additonal movement. See Pic #4. I removed the PKlamp and main clamp bolt to check crank endplay. It was unchanged at 0.008" (the same reading for years). Here's a description of how I check endplay: https://rennlist.com/forums/928-foru...pictorial.html The main clamp bolt sure did not feel like my usual 62 ft lbs when I loosened it. Anyway, I retorqued it and the PKlamp. Pic #5 - New paint mark after checking crank endplay and retorquing PKlamp and main clamp bolt.
Update #4: 02/14/2011, 9,250 miles since I reset the clamp, 228,371 on odo - no movement.
Update #5: 10/13/2011, 20,300 miles and 15 months since I reset the clamp when doing crank endplay check - 239,421 on odo - no movement. See Pic #6. I will be loosening the clamp since I need to repair the torque converter seal in my tranny. Time for my annual endplay check anyway. So, the interval willl start over. This 20K mile interval with no movement is long enough to make me believe the PKlamp is doing what Ken intended. In the past, before I added the PKlamp, it took no more that a few K miles to get 1-3mm of movement.
11/15/2011 - the tranny is out for leak repair. So, the next check will be a fresh start for the PKlamp.
Update #6: 06/30/2012, 3,457 miles since I reset the clamp after the tranny work, 242,878 miles on odo - no movement. Left it alone, of course.
08-04-2009, 05:51 PM
#2
Nordschleife Master
NICE! If that continues this will prove to be a MUST have for the Auto S4's and newer! It could ultimately be one of those things that are looked for when buying a used 928 that makes or breaks the deal even!
08-04-2009, 05:53 PM
#4
Shameful Thread Killer
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Well, I'll wait for someone who can actually put some stress on the thing before I get one.
haaaaaaaaaahahahhahahahhahahahhahaha!
haaaaaaaaaahahahhahahahhahahahhahaha!
08-04-2009, 05:57 PM
#6
Under the Lift
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Yeah, this 4000 miles wasn't that stressfull. I was having trouble getting my car to do anything resembling a burnout in Texas. Not sure what the problem was, but when I got back near home, WHOAH! The Force is back! Had a nice drag race with some kind of ricer vehicle near Bakersfield.
08-04-2009, 06:07 PM
#7
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Bakersfield? And you got out alive? Wow, that is news worth reporting. Bakersfield in August, it's hard for someone in TX to pity someone else's heat but, really......
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08-05-2009, 02:42 AM
#12
(Apologies in advance if this comes through twice - internet server died at submittal point)
If the central shaft wants to pull back (for whatever reason - the reason not being the subject of this post) and you lock it to prevent it from doing so then yes you prevent the effective length of the shaft increasing and therefore prevent the front face of the thrust bearing from coming under pressure.
But doesn't that also mean that at those times when the engine is running and the the shaft is 'straining' and 'trying' to pull out of the flex plate clamp then the rear face of the thrust bearing will now be under pressure and that face will now wear instead?
The wear effect may be much less pronounced though, since with the stronger clamp that new pressure will only occur at the times that the shaft is 'trying' to pull back, whereas with the standard weak clamp when the shaft pulls back - and does not push back of its own accord - it ends up applying forward thrust all the time?
On the other hand, the 'pulling back' pressures (that maybe don't occur all of the time that the engine is running?) that are now being prevented may be stronger than the resulting forward thrust once pulled back, or the shaft would indeed re-push forward through the clamp to its 'home' posiition.
So does this type of much stronger clamp change the dynamics from a Constant [ :-) ] forward thrust on one face of the thrust bearing to a much stronger intermittent pull on the other side of the thrust bearing?
I freely admit that I've done no practical tests on this issue (I know many have) but have been thinking about it on and off for years. From an applied theoretical perspective l reckon a high speed 'slip joint' between two central shaft 1/2s, somewhere in the middle of the torque tube between the bearings would be a better approach in principle. Then the central shaft would be able to change its effective length (for whatever reason) by some mm without putting strain on the flex plate etc. Much more expensive to design, construct and install. Probably prohibitively expensive, but...
Just some thoughts.
If the central shaft wants to pull back (for whatever reason - the reason not being the subject of this post) and you lock it to prevent it from doing so then yes you prevent the effective length of the shaft increasing and therefore prevent the front face of the thrust bearing from coming under pressure.
But doesn't that also mean that at those times when the engine is running and the the shaft is 'straining' and 'trying' to pull out of the flex plate clamp then the rear face of the thrust bearing will now be under pressure and that face will now wear instead?
The wear effect may be much less pronounced though, since with the stronger clamp that new pressure will only occur at the times that the shaft is 'trying' to pull back, whereas with the standard weak clamp when the shaft pulls back - and does not push back of its own accord - it ends up applying forward thrust all the time?
On the other hand, the 'pulling back' pressures (that maybe don't occur all of the time that the engine is running?) that are now being prevented may be stronger than the resulting forward thrust once pulled back, or the shaft would indeed re-push forward through the clamp to its 'home' posiition.
So does this type of much stronger clamp change the dynamics from a Constant [ :-) ] forward thrust on one face of the thrust bearing to a much stronger intermittent pull on the other side of the thrust bearing?
I freely admit that I've done no practical tests on this issue (I know many have) but have been thinking about it on and off for years. From an applied theoretical perspective l reckon a high speed 'slip joint' between two central shaft 1/2s, somewhere in the middle of the torque tube between the bearings would be a better approach in principle. Then the central shaft would be able to change its effective length (for whatever reason) by some mm without putting strain on the flex plate etc. Much more expensive to design, construct and install. Probably prohibitively expensive, but...
Just some thoughts.
08-05-2009, 02:45 AM
#13
Inventor
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So ... there is a LOT if you search archives. Short answer to your post.
08-05-2009, 03:47 AM
#15
Hi Heinrich, yip out of that part of the world now. And very pleased too.
I like the way you so succinctly destroyed my elaborate theory :-). Which part of my theory did your answer apply to:
a) The lot
b) The bit at the start
c)The bit in the middle
d) The bit in the end
e) Two of the above, etc
But seriously, yes I've read just about every post over the past 5 years or so, with particular interest in this issue. Yes there are lots of posts of theories as to why this is happening, and solutions how to stop it happening. But I have yet to see any post that addresses why - by stopping the central shaft pulling back through the flex plate even though it stall wants to - you are not creating a situation where the other side of the trust bearing will now be wearing. After all, the forces are still there, just clamped tighter so there is no movement between the two mating parts. The flex plate will instead be being pulled back, along with flywheel and crank. Won't it. (I can guess your answer - "No"). :-)
Cheers mate
PS Bill - is this discusion that I have started hijacking your thread or is it a legitimate thing to raise within your thread.
I like the way you so succinctly destroyed my elaborate theory :-). Which part of my theory did your answer apply to:
a) The lot
b) The bit at the start
c)The bit in the middle
d) The bit in the end
e) Two of the above, etc
But seriously, yes I've read just about every post over the past 5 years or so, with particular interest in this issue. Yes there are lots of posts of theories as to why this is happening, and solutions how to stop it happening. But I have yet to see any post that addresses why - by stopping the central shaft pulling back through the flex plate even though it stall wants to - you are not creating a situation where the other side of the trust bearing will now be wearing. After all, the forces are still there, just clamped tighter so there is no movement between the two mating parts. The flex plate will instead be being pulled back, along with flywheel and crank. Won't it. (I can guess your answer - "No"). :-)
Cheers mate
PS Bill - is this discusion that I have started hijacking your thread or is it a legitimate thing to raise within your thread.