Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

My Flexplate - Crank Endplay Check Pictorial

 
Old 06-26-2007, 09:07 PM
  #16  
Garth S
Addict
Rennlist Member
 
Garth S's Avatar
 
Join Date: Oct 2003
Location: Nova Scotia
Posts: 7,203
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by StratfordShark
Great write-up thanks.

2 questions:

Do you think it's possible to do this job on axle stands/ramps (I have enough room to get pans off when it's on ramps) or is it essential to get it up on a lift?

What kind of tool is a "sawzall" if I use the trick of cutting off bolt heads, and as an aside is there any potential problem with only having 4 bolts on the bell cover?
Here's an approach on lopping off bolt heads ... but not with a real sawzall: anything is possible I suppose ....
Garth S is offline  
Old 06-26-2007, 09:12 PM
  #17  
AO
Supercharged
Rennlist Member
 
AO's Avatar
 
Join Date: May 2002
Location: Back in Michigan - Full time!
Posts: 18,899
Likes: 0
Received 0 Likes on 0 Posts
Default

Bill-
Wonderful writeup. It's so good, I think I'll give it a try one of these days!
AO is offline  
Old 06-26-2007, 09:16 PM
  #18  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
Thread Starter
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by dr bob
Bill,

What's the reason for preloading the cran forward against the thrust bearing? I thought we were trying to eliminate the preload in that direction...

I left mine midway, FWIW.
Ooops! That's written backwards. I didn't do that at all. Let me fix that!
Bill Ball is offline  
Old 06-26-2007, 09:17 PM
  #19  
F451
Super User
 
F451's Avatar
 
Join Date: Jan 2006
Location: WA
Posts: 3,256
Likes: 0
Received 0 Likes on 0 Posts
Default

Excellent write up Bill. This will be very useful for so many people.

I just checked the flex plate tension on my '85 and did the exact same thing you did with a ruler. Measured it from a few different spots and could find not any bowing of the plate. I did release the clamp just for the hell of it, and detected no movement at all, as I expected.

I did not do the crank endplay check as I wasn't sure what to do, now I can get back under there and check it out.

And for the lower bellhousing cover, I managed to get all of the bolts out on my '85. It was a real bear and took some time, but I did get them out.
F451 is offline  
Old 06-26-2007, 09:19 PM
  #20  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
Thread Starter
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by docmirror
Please 'splain this part:

15. Push the crank back to the front

Very detailed. Should be required procedure for any 928 auto owner.
I'll 'splain it by saying it's wrong and I didn't do that. I actually pulled it to the rear. No preload, just moved to the rear, but definitely not the front. Let me fix that.


....FIXED! Thanks to you and dr. bob for picking up my mental lapse during the write-up.
Bill Ball is offline  
Old 06-26-2007, 09:26 PM
  #21  
Mrmerlin
Petie3rd
Rennlist Member

This Post Sponsored by:
Dow Corning« & DeoxIT«
 
Mrmerlin's Avatar
 
Join Date: May 2004
Location: Philly PA
Posts: 22,744
Received 3 Likes on 2 Posts
Default

I have been prying the crank to the rearmost travel then tigtening the bolt to 66ft/lb , since the driveshaft likes to grow in distance it seems logical to give the system the most travel, we are not talking much travel but any little bit helps.
Bill, Nice pictures and writeup, it would also be interesting to see what the readings would be if you took them on the flywheel instead of the flexplate, as the flexplate can move or not move on the driveshaft possibly due to locktite.
Also if there is found to to be a lot of preload on the flexplate, this should require that the rear pinchbolt be checked and refitted and torqued to 66ft/lb, this requires that the exhaust system be removed to gain access to the rear driveshaft. I know there is a relief cut into the rear driveshaft where the bolt passes but this wasnt made to hold the bolt/clamp in a certain position, Stan
Mrmerlin is offline  
Old 06-26-2007, 09:35 PM
  #22  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
Thread Starter
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

Stan:

I have no loctite on the shaft. There isn't supposed to be any, and it's pretty clear that anything short of red Loctite doesn't stop the shaft from moving, so I don't use it.

Certainly, you could measure at the periphery. I should have done it both ways because it is probably easier to position the gauge at the periphery anyway. It's just that that is where I pry on the flywheel. I don't think I'm flexing the flywheel, but it seemed the center would be more relavent, obviously providing the flexplate is perfectly free to move, as mine was.

Another afterthought - I should have checked the endplay WITHOUT releasing the TT clamp, and checked it at the crank pulley or the crank bolt, as well. We like to release the TT clamp anyway, but it would be worth doing this other way to see if that could work for the Red Loctite crowd, as well as serve as a quicker external check. Oh, I recall now that Garth has already done this, although w/o a direct comparision.

Last edited by Bill Ball; 06-26-2007 at 10:03 PM.
Bill Ball is offline  
Old 06-26-2007, 09:41 PM
  #23  
wds928
Addict
Rennlist Member
 
wds928's Avatar
 
Join Date: Apr 2004
Location: Charlottesville, Virginia
Posts: 812
Likes: 0
Received 0 Likes on 0 Posts
Default

Bill, great writeup and pictures. The underside of your car is way too clean!! Printing this out now and will do this weekend, as I haven't done it yet.
wds928 is offline  
Old 06-26-2007, 10:00 PM
  #24  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
Thread Starter
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Garth S
Here's an approach on lopping off bolt heads ... but not with a real sawzall: anything is possible I suppose ....
Yeah, that's what I was refering to. Sorry to have accused you of using something so crude as a Sawzall.
Bill Ball is offline  
Old 06-26-2007, 10:01 PM
  #25  
Jim R.
Addict
Rennlist Member

 
Jim R.'s Avatar
 
Join Date: Mar 2004
Location: Long Island, New York
Posts: 908
Likes: 0
Received 0 Likes on 0 Posts
Default

Bill,

Great writeup!
If I buy another 928 with an automatic, this has got to be part of the PPI and yearly maintenance program.

This definitely needs to be put up in the 928 DIY section. Very slim pickings there, and this is perfect material.

Jim
Jim R. is offline  
Old 06-26-2007, 10:53 PM
  #26  
docmirror
Shameful Thread Killer
Rennlist Member
 
docmirror's Avatar
 
Join Date: Aug 2004
Location: Rep of Texas, N NM, Rockies, SoCal
Posts: 19,576
Likes: 0
Received 5 Likes on 4 Posts
Default

Originally Posted by Bill Ball
I'll 'splain it by saying it's wrong and I didn't do that. I actually pulled it to the rear. No preload, just moved to the rear, but definitely not the front. Let me fix that.


....FIXED! Thanks to you and dr. bob for picking up my mental lapse during the write-up.
No prob, I've made far worse. Dr Bob felt it needed further questioning.
docmirror is online now  
Old 06-27-2007, 04:26 AM
  #27  
Tails
Addict
Rennlist Member
 
Tails's Avatar
 
Join Date: May 2001
Posts: 1,113
Likes: 0
Received 7 Likes on 7 Posts
Default

Bill,

Excellent write up, enhanced tremendoulsy by the photographs. How did we ever write such clear reports without digital cameras?

As my car is not fitted with cats, it is easy to remove bell housing, so all bolts are refitted. During inspections I have removed the bell housing, released flexplate clamp, renewed set screw, reclamped up to torque setting plus 10% and painted clamp and torque transmission shaft splines.

Initial inspections done via drain hole with a small light on fixed extension piece to view migration via gap in paint.

Initial migration measured at 3.08 mm with crankshaft end play at 0.008 inches. Every year detected migration to a lesser degree, but seeing still getting movement resorted to loctite 290 in 2006 as Garth has done.

Each time when I reclamped I would move the crankshaft forward against the thrust bearing and then clamp, as this gave me 0.008 inches movement during windup of torque transmission shaft (shortening due to twist up) and its drawing out of clamp in a aft direction. As previously stated every little bit of clearance before draw out begins is helpful.

In February this year at the yearly service (12 months since loctite applied) no movement of flexplate clamp detectable via paint. This was doubly checked by measurement from bell housing to flexplate flange via inside calipers and measurement remained the same, no migration.

I tried to measure crankshaft end play, but got no movement as probably not enough force applied. I was a little reluctant to apply too much force. Maybe next time I will give it a bit more to see if I can detect thrust bearing clearance as stated by Garth.

With write ups like yours my 928 technical library is growing.

Keep up the excellent work.

Tails 1990 928 S4 Auto
Tails is offline  
Old 06-27-2007, 04:32 AM
  #28  
IcemanG17
Super User
 
IcemanG17's Avatar
 
Join Date: Sep 2004
Location: Stockton, CA
Posts: 15,996
Likes: 0
Received 0 Likes on 0 Posts
Default

Bill
Great write up......you got the exact same result I did a little over a year ago

https://rennlist.com/forums/showthre...ight=flexplate
IcemanG17 is offline  
Old 06-27-2007, 06:51 AM
  #29  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
Thread Starter
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Tails
Each time when I reclamped I would move the crankshaft forward against the thrust bearing and then clamp, as this gave me 0.008 inches movement during windup of torque transmission shaft (shortening due to twist up) and its drawing out of clamp in a aft direction. As previously stated every little bit of clearance before draw out begins is helpful.
This is the opposite of what I did. It's a good question as to which side of the thrust bearing sees the most load, and if there is any measurable wind-up shortening of the TT. Since I always have found the crank pressed forward by the TT, I've thought to not only relieve the pressure but move the crank back, so, in theory, it would take longer before it accumulates preload. I need to rethink this.

I tried to measure crankshaft end play, but got no movement as probably not enough force applied. I was a little reluctant to apply too much force. Maybe next time I will give it a bit more to see if I can detect thrust bearing clearance as stated by Garth.

Tails 1990 928 S4 Auto
Even if you are pushng against the flexplate, it shouldn't take that much force to move the crank the tiny distance involved. I'm going to try doing an external endplay check at the front crank bolt myself tomorrow.
Bill Ball is offline  
Old 06-27-2007, 07:43 AM
  #30  
Black Sea RD
Addict
Rennlist Member
 
Black Sea RD's Avatar
 
Join Date: Feb 2004
Posts: 2,137
Likes: 0
Received 0 Likes on 0 Posts
Default

I wasn't going to post since I do not want to seem as a party pooper or nay sayer, but...

We did a pretty extensive research into this whole affair and it's relation to TBF. We studied the Porsche workshop manuals and they describe a procedure on how to set up the flexplate and flywheel currently. I would use this new procedure and not deviate from it.

The 66 ft lbs. of torque currently being used by many at the front pinch bolt actually came from a post long ago from a gentleman who was chasing around the whole driveshaft pullout in his car. His mechanic shop placed a call to Porsche AG who advised to use this new torque rating *and* change the the front flexplate with a new one. Over the years the new front flexplate seemed to be forgotten as the other part of the equation since it's expensive and not easy to do. We found using the higher torque rating had minimal to no effect even with a new pinch bolt. The reason being the front flexplate clamp is not designed to be re-used much and after a time stretches out and cannot hold as well.

As always we do not recommend using loctite to fix the driveshaft pullout since it can cause problems for the owner later.

This posting in no way is meant to diminish the excellent write up by Mr. Ball on checking the front flexplate and thrust bearing for this problem. The Porsche workshop manuals also describe how to check thrust bearing wear for any who are intersted to do so.

Constantine
Black Sea RD is offline  

Thread Tools
Search this Thread
Quick Reply: My Flexplate - Crank Endplay Check Pictorial


Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: