My Flexplate - Crank Endplay Check Pictorial
 

LATE EDIT: I should give credit to Tony Harkin for his nice write-up of the procedure that I just found after writing mine below. I like his even better. He used a simple micrometer to measure between the ring gear and the block. Very nicely done, Tony!
http://members.rennlist.com/v1uhoh/cranksha.htm
----------------------------------------------------------------


My car has 182K miles on it and gets treated to some high-speed stress in the Nevada desert a few times a year as well as routine driving, occasional burnouts and funrides in the local twisties. Because it is an AT, I check the flexplate preload every few months but haven't done crank endplay in at least 5 years. I almost always find 2-3mm of flexplate preload, but never more. The crank endplay was good when I checked it 5 years ago.

After a report yesterday of a car with some symptoms of TBF and 1/2 inch of preload found on the flexplate, I decided it was time for an endplay check.

Here's what I did.

1. Gathered these tools.
- torque wrench
- extension, adapter
- 8mm Allen
- prybar
- straightedge
- dial gauge accurate to .001 inch with mounting base and arms
- ratchet, extension and 13mm socket
- worklight
- 5/16ths (eh, 8mm seems too large) nut driver for bellypan screws. Many people will find some 10mm screws as well.
http://billsworkshop.com/P928S4/endplay/endplay01.jpg

2. Get the car in the air. Looking up in the area you need to work on, this is what you see - the rear bellypan needs to be removed. Front bellypan can stay in-place.
http://billsworkshop.com/P928S4/endplay/endplay02.jpg

3. After you remove the rear bellypan, the lower bellhousing cover is exposed. It is held on by 6 hex bolts with 13mm heads, 4 of which you can see in this photo.
http://billsworkshop.com/P928S4/endplay/endplay04.jpg

4. If this is the first time you have done this and you have the stock exhaust and cats, you will be confronted with a problem getting the two rear bolts out of the cover. They are trapped by the H-pipe area. I have been in here many times, so I left those bolts out long ago. You probably will have to remove the front exhaust from the manifold and let it dangle down to get these bolts out. This is a real nuisance, as you will find if you have to do it. The exhaust bolts are often rusted on hard and require a variety of wrenches due to awkward locations and counterholding the bolt heads. Also, to separate and lower the front exhaust even a bit, the two lower 19mm bellhousing to block bolts must be loosened as they hold brackets to a couple of the exhaust bolts. Finally, the joint in the air line to the catalytic converted must be opened. Ugh! After the first time doing this crap, some people will shorten the rear cover bolts so they can be removed with the exhaust left untouched. I just left them out. When I shortened them, they were still trapped by the exhaust. Some have used a Sawzall the cut those bolts out rather than drop the front of the exhaust at all.
http://billsworkshop.com/P928S4/endplay/endplay05.jpg

5. Once the lower cover is off you will see the flexplate and clamp. Here it is positioned so I can't get to the clamp bolt head to loosen it.
http://billsworkshop.com/P928S4/endplay/endplay06.jpg

6. I use a prybar/large screwdriver to move the flywheel. The ring gear and flywheel on later cars are one piece and can be handled this way. The engine should only be rotated clockwise (which would be counterclockwise back at the flywheel). You could use a 27mm socket on the front crank bolt instead or tweak the starter until the bolt head is accessible.
http://billsworkshop.com/P928S4/endplay/endplay07.jpg

7. Now I can see the 8mm Allen head.
http://billsworkshop.com/P928S4/endplay/endplay08.jpg

8. Before loosening the clamp bolt, lay a straightedge across the flexplate. This isn't the best straightedge, but as you can see there is a tiny but insignificant bowing. There have been some reports of finding as much as 10mm bowing in some cars. As much as 1 or 2mm wouldn't bother me too much, but anything more would mandate an immediate endplay check after releasing the preload.
http://billsworkshop.com/P928S4/endplay/endplay09.jpg

9. Loosen the clamp and observe the clamp and flexplate for movement. I think the clamp moved maybe 1/2 mm (compare the photos above and below). This is after I had beat the crap out of the car in the Nevada desert earlier this month. As you can see, I have very little of the splines showing. This seems to have decreased over the years, and you can speculate as to why. The TT is original. A few years ago the tranny was moved once back 1 inch so I could replace the rear main seal, and then slid forward back into position, but otherwise nothing has moved or been removed at any time. That should not have changed the geometry as the TT was left attached to the tranny when it was moved back and forth.
http://billsworkshop.com/P928S4/endplay/endplay10.jpg

10. So much for the flexplate. Now it's time for crank endplay. Leave the clamp loose. Position a dial gauge against the clamp base. Actually you could measure at any of several places. You guys can argue about that, but this location, even though it is on a part of the flexible flexplate, is fine if the clamp is nice and loose. Others would use the more solid starter ring gear rear face, shown in the second of two photos below. I have the magnetic base mounted on the exhaust pipe. It took some maneuvering to get the dial gauge hardware lined up well enough.
http://billsworkshop.com/P928S4/endplay/endplay11.jpg

http://billsworkshop.com/P928S4/endplay/endplay11a.jpg

11. Lever the flywheel toward the front of the car with the prybar and zero the dial gauge. I set the gauge several thousandths below zero and use this angle adjustment to bring it up to zero, assuring good contact at zero. Note the prybar tip between the bellhousing wall and the flywheel. You don't have to pry hard; just enough to make sure it is seated. Hard or soft prying will seat it firmly with no additional movement.

http://billsworkshop.com/P928S4/endplay/endplay12.jpg

12. Zero'd, crank forward. Ready to go.
http://billsworkshop.com/P928S4/endplay/endplay13.jpg

13. Pry the flywheel to the rear. You should hear a small clunk as it moves. Keep modest pressure against the flywheel so it doesn't slip back on its own.
http://billsworkshop.com/P928S4/endplay/endplay15.jpg

14. Observe the reading. 0.008 inch. Release, pry the flywheel forward and observe if the gauge is again zero (mine was), then pry to the rear again and check the endplay reading again. Mine was 0.008 inch both times. That's 0.20 mm. Lucky me. That is essentially factory. The spec limit is 0.40mm (0.016"). Anything above that and the motor should be pulled for a rebuild. The stated range in the WSM (volume 1, section 13, page 8) is: New 0.110 to 0.312mm (0.004 to 0.012") with a 0.40 mm (0.016") wear limit.
http://billsworkshop.com/P928S4/endplay/endplay16.jpg

15. Leave the flywheel in the rear position with no preload, torque the TT clamp bolt to 62 ft lbs (some use 66 ft lbs, others red Loctite the clamp to the TT, etc.). Put the bellhousing cover and rear bellypan back on, lower the car and go for a celebratory burnout!

Nice writeup Bill!

That makes a lot more sense when you can actually see what you are supposed to do. Thanks for that.

:thumbsup:

Thanks Bill.

Another project to add to the PM list.

Please 'splain this part:

15. Push the crank back to the front

Very detailed. Should be required procedure for any 928 auto owner.

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?

Excellent write up.

Thanks for the time and effort to capture this !!

Fantastic job.

Thank you

As with the others statements, kudos to a great writeup. Anyone with an A/T that hasn't done this yet is NUTS! (Ahem Sean!!)

As you mention, the worst part is dealing with the rear bolts the first time around. Since you need to drop the exhaust to get to these, it's an excellent time to do an X-pipe for those on the fence....

Now, that I'm on my soapbox, I should preach to myself: I've not checked mine in 13 months.

BTW, it looks nice and clean there under her skirt. I'd hit it.

Nice write-up Bill !!!

The Mad Scientist Rides Again :bowdown: :bowdown: :bowdown:

Great write up Bill, especially with the pics! :thumbup:
Soooo,.... when are you movin to Sunny Florida anyways?? We need ya down here! :bowdown:

Ah the internet. If only folks would learn the concept of search;

http://www.milwaukeeconnect.com/weba..._192213_192137

Yes, possible to do on stands/ramps. No prob with only four bolts in the bottom cover.

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... :confused: :confused: :confused: :confused:

I left mine midway, FWIW.

nice work Bill!