Crank thrust bearing issues
08-21-2005, 01:19 PM
#18
Pro
Thread Starter
If you just jumper the switch the cruise control probably won't work. I was hoping there was a separate relay for this function.
PorschePhD, can I do a crude check of the end play by (carefully) prying on the front pulley or something like that? What is the old vs. new end play spec?
PorschePhD, can I do a crude check of the end play by (carefully) prying on the front pulley or something like that? What is the old vs. new end play spec?
08-21-2005, 01:23 PM
#19
Rennlist Lifetime Member
You are correct. The problem with the spec is checking it as it needs to be unloaded, but the issue is according to spec it is in. You can pry on it with the belt off and I will bet my last dollar you have enough play in it you can see it move. There is no way to tighten the spec other than welding the crank and turning it back down. Not practical
08-21-2005, 01:50 PM
#21
Three Wheelin'
stephan,
I haven't built a 996 tt motor, but have built other earlier air-cooled Porsches, VW, and Carrera engines. And many different other types of engines. In my earlier years I did quite abit of wrenching, so I have a decent understanding. Fun and enjoyed working on my personal projects but didn't enjoy it enough to do it for a living.
I would like to see a pic of the bearing thanks. When you upgrade your HD clutch kit how do you address this? If you upgrade to the GT2 clutch pressure plate or any other HD kit this would exacurbate the problem sooner. Isn't possible to shim the crank for correct end-play?
I haven't built a 996 tt motor, but have built other earlier air-cooled Porsches, VW, and Carrera engines. And many different other types of engines. In my earlier years I did quite abit of wrenching, so I have a decent understanding. Fun and enjoyed working on my personal projects but didn't enjoy it enough to do it for a living.
I would like to see a pic of the bearing thanks. When you upgrade your HD clutch kit how do you address this? If you upgrade to the GT2 clutch pressure plate or any other HD kit this would exacurbate the problem sooner. Isn't possible to shim the crank for correct end-play?
08-21-2005, 04:02 PM
#22
Rennlist Lifetime Member
If you have done Carrera motors then you would know if the thrust is out then you address the issue by replacing the crank. Shims should never be used and is a band-aide that will leave a motor with problems down the road.
There are several issues as I have stated, overall drag, the spec by which Porsche sets the crank, the clutch. My point is it is going to wear regardless of the clutch. The issue is with the spec sent from the factory. Why do I say this? The GT2 motor I just built with 6K on it is a Euro import. That means no clutch on start up. I have seen it in several tip motor, no clutch on start up. The issue is present. This is more than one issue with the wear.
Do I think where is accelerated with the clutch, I thought so until I did the tip and the euro motor. Think about the one thing that has changed on the motor and what might cause pressure on the crank? It is not the clutch
Oversize bearings do not effect the thrust size. The crank will determine thrust spec on a new bearing.
There are several issues as I have stated, overall drag, the spec by which Porsche sets the crank, the clutch. My point is it is going to wear regardless of the clutch. The issue is with the spec sent from the factory. Why do I say this? The GT2 motor I just built with 6K on it is a Euro import. That means no clutch on start up. I have seen it in several tip motor, no clutch on start up. The issue is present. This is more than one issue with the wear.
Do I think where is accelerated with the clutch, I thought so until I did the tip and the euro motor. Think about the one thing that has changed on the motor and what might cause pressure on the crank? It is not the clutch
Oversize bearings do not effect the thrust size. The crank will determine thrust spec on a new bearing.
08-21-2005, 04:13 PM
#23
Three Wheelin'
I have not heard of any catastrophic failures due to this. At 6k miles and a noticeable wear and this is as common as you say, It could be that it is engineered into the overall wear of the motor. There a many high mileage turbos running around with no problems. Thanks for the info. Let's see some pics of this wear.
08-21-2005, 06:45 PM
#24
Rennlist Lifetime Member
Truly Oak you are really not that naïve? Are you honestly suggesting that Porsche is purposely building premature wear into the thrust?? Since you have a vast experience with Porsche motors you might want to explain to the masses what that might do to the engine and drive-train. Here is a hint, if you are not sure of the answer call the 928 guys. They can help. Do you think that bearing rattle on startup is normal? The issue is present and you are nuts to think Porsche would say it exist. I know of several local cars that got motors, their reasoning was to much tension on the motor. That caused the rattle. LOL, ya right. I am running up to work right now to grab you a picture.
08-21-2005, 07:46 PM
#25
Rennlist Lifetime Member
Here ya go Oak. The first picture is the odometer for verification.
Here are the two halves. Notice the wear on the shoulder then the premature wear on the face from the slap and lack of oil on startup.
Then for the heck of it I pulled some of the lower shells from motors I have done.
Here are the two halves. Notice the wear on the shoulder then the premature wear on the face from the slap and lack of oil on startup.
Then for the heck of it I pulled some of the lower shells from motors I have done.
08-22-2005, 12:04 AM
#28
Rennlist Lifetime Member
Mike,
There are some things that we have talked about trying. All of these show within spec in the motor, but clearly are wearing too soon.
well I wish I was that good at photoshop. If I was bearings would not be what I would change 
There are some things that we have talked about trying. All of these show within spec in the motor, but clearly are wearing too soon.
well I wish I was that good at photoshop. If I was bearings would not be what I would change
08-22-2005, 10:48 AM
#30
Rennlist Lifetime Member
Anything is possible, but the third bearing in the bunch never ran 0 or 5 weight with the exception of delivery. Ran a 15 from the first oil change. The bottom line is the thrust spec is to high and the loag on the nose is too much.