- check your flanges to make sure the bolt holes are not run out (due to joint coming loose). if the flange holes are egged, I think this contributes to the bolts loosening.
- ditto for the CV joint holes, they will egg too.
- yes, check the tranny mount
- when installing the bolts, I've had the best luck when I've lubed them lightly with oil and then used a 2 stage torque down with a star pattern
Agree with Jeff. Lightly lube the bolt. Lubed threads results in more of the torque transferred to stretch and its a more consistent torque that way. Make sure you are using the right spec bolts, they are high strength 12.9's. Double check for torque.
With the right bolts, the right sequence, I have never seen a problem. You don't need new bolts each time as some believe, but there is no harm, as long as they are the correct grade. I wire mine for security, but its not really necessarry just precautionary.
There should be no lube between flanges. The joint is like a clutch, the bolt torque/stretch puts clamp force on the flanges, and its the friction force that keeps the joint from moving. Dry flanges, lubed bolt threads only.
The two statements are not in conflict. TTY does not mean throw the bolts away. Like I said I only wire as a precautionary. I wouldn't waste my time for a street car, nor am I suggesting a need to wirelock. Like I also said, if you want to use new then obviously its OK, I didn't say don't do it, using new bolts for any maintenance is never a bad idea. It can be misleading suggesting its used bolts that may be the problem its not.
If the joint is loosening up, especially in such a short time, somethings not right.
Porsche head studs are TTY, there is no requirement to replace.
The last thing you want to do is start loctiting. You have to make sure the hardened plates are also used.
I used new bolts, torqued to spec and still had them come loose in racing applications. I now also wire mine to be on the safe side. However, I just today serviced the halfshafts in my street S2. Reused the bolts, torqued to spec. 30 lbs. I'll let you know if they come loose.
Don't tell people not to get new bolts and THEN mention that you wire yours. The two statements go against each other. Porsche has spec'd these bolts as a TTY, or torque to yield. You torque the bolts until they yield (stretch) and when removed, they need to be replaced. I don't see the big deal anyway since Pelican has them for $0.75 a piece. Cheap insurance if you ask me.
I ordered a set from Pelican and was disappointed they were regular hex bolts and not the triple squares. There was a group buy on Stage 8 locking bolts for this a while back. Maybe someone has a set they will sell and/or Stage 8 may stock them now. I also use a star pattern in multiple stages (triple checking them all once done) and generally have no problems.
No were in the manual have I seen that these bolts are TTY and should not be reused. I have always used new bolts since the force on them is high, they are cheap and it seems like a good precaution. Last set I put on were Stage 8 locking bolts which appear to address this issue of backing out but they stilll need to be properly torqued.
Personally, I have started to wonder if this problem isn't related to the mileage on some of our cars. If you've had a couple episodes of loose bolts, I think the flanges get egged out and it's harder for the bolts to remain torqued.
Differences by car in the flange condition could help account for the widely varying experiences everyone seems to have on the board. I do like the stage 8 bolts and will likely go that way next time I have an extra $80 burning a hole in my pocket.
I had this problem on an 89 S-2 that I used to race. The bolts would keep coming loose after (and sometimes during) every run session. I came to the conclusion that when they loosen up, grease gets between the two mating surfaces, so just re-torquing them doesn't last and just makes the problem worse. I found that after cleaning the surfaces carefully and re-assembling them (making sure to keep the surfaces dry) they stayed put. I marked the bolts as Tony suggested and they never moved again. This was my experience. Yes, I re-used the bolts.
With my current Turbo race car, I did this and they have not moved. I check them after every race along with every other nut and bolt.
85.5 944 SPEC
2008 Cayman S
Gone but not forgotten:
1989 944 S2
1989 944 Turbo (400 RWHP)