99 boxster clutch
 

Hi, Doing my clutch and new DM flywheel on 99 boxster base.Few questions.

Torque for flywheel factory manual says 18 ft lbs + 90 degrees Bentley says 19+120 degrees think I'm gona go w factory manual..???

Torque for 3 bolts for throw out bearing guide tube Bentley has nothing factory manual says 26 ft lbs I went with this and used Loctite wicking threadlock

Factory manual says only grease input spline does anything else need to be greased in there??

thanks

I belive a spot of lithium grease goes on the pivot for the throwout arm pivot.

Always, always always use the torque setting provided by whoever supplied the fasteners. If they didn't tell you, I'd default to the factory manual. (and if you're reusing fasteners, then you're on your own.... I wouldn't in this application)

And don’t use any lubricants. They’ll change the torque value of the hardware drastically.

Nonsense. USING the proper lubricant will give you the most accurate torque readings.

It depends on how the torque spec was originally designed, with lube or dry.

For example, Porsche does not specify any lube on wheel lug bolts, so lube would cause actual torque above the spec.

I would suggest you read ARP’s white paper on the subject of reproducible torque levels and how they cannot be achieved without proper lubrication. The random scatter of torque readings without lubricant demonstrates why ANY fastener with a torque setting needs to be correctly lubricated in order to achieve the desired clamping loads.

Porsche does specify that you should use no seize on the wheel bots and that you should be careful not to get any on the conical part that connects with the wheel.

We use nickel anti seize on every Porsche wheel bolt that passes through the shop, have for decades, and have never had any issues. We have, however, seen multiple cars that were in for the first time with severely galled wheel bolts from not using anti seize, and which required us to make remedial repairs to the hubs and replace the wheel bolts with new.

We also do this on every car that passes through the shop, from VW's to Ferrari's, including center lock wheels.

It does not take much imagination to predict relatively poor gage R&R with dry torque vs lubed... My point was to clarify if the spec is meant for lubed or dry condition.

If you lube and torque to the dry spec., it will be over tightened, it's the fact. Still you may have no issues if the clamp force is still under the material yield, which could be the most cases where components are designed with safety margin, especially Porsche.

Okay I was not aware of this... Somehow I though Porsche changed recommendation from lube to dry.

I lubed lug bolts for the last 3 decades with all other cars I owned and maintained, mainly Europeans incl. 914 and 3 generations of SAABs, with no issues. It is rather recentlly for the last 2 years of my Boxster ownership that I just clean bolts with a wire brush and dry-torque, assuming the 96 ft-lb spec based on dry especially as it seems relatively higher than typical 80 ft-lb spec. with other OEM's in my experience. I daily drive mine through MI winter and no corrosion issues when I change wheels/ tires twice a year.

Anyway I guess I'd go back to lube if that's what the P-doctor orders.

The entire point of the ARP paper was to demonstrate that you cannot reproduce the intended clamping force without proper lubrication. The torque spec is to get that clamping force level, which you may, or more probably may not get when applying torque to dry fasteners. In their research, ARP looked at the actual achieved clamping load vs the observed torque readings; when the fasteners were torqued dry, the clamping load was all over the place; sometimes high, more often too low. When lubricated, the specified torque readings uniformly produced the expected clamping loads.

Again the point is if the spec was designed for dry or lubed condition. Dry spec can be developed to statistically assure the min clamp force for the application and still under material yield. It is risky to torque with lube when the spec really meant for dry...

I’m sure ARP as a fastener company advocates lube that reduces variations and achieves clamp force intended as consistent as possible for their optimal design without overengineering.

It was just not clear to me if Porsche spec. was based on dry or lubed, as I have not seen factory document specifying to lube.

And again, the point of any torque spec is getting the correct clamping force between two parts, which is rarely achieved with out proper lubrication of the fastener being torqued.

I know you are the expert:)

Just saying that proper clamp force (or practically anything) has some acceptable tolerance range, and dry spec can be (should be) developed based on variations from components, friction/ stick-slip, etc. and yet to assure the clamp force in the proper range, instead of hitting the exact number... I do not have a fancy torque wrench with precise load-cell either but assuming some gage error is in the factory equation of the spec.

I do not have factory service manual but the owners manual and Bentley I have handy do not indicate to lube....

And just for reference... 718 manual says NOT to grease (lube) those bolts... I know, different car/ design but.

Attachment 21762

Sorry OP asking about the clutch, did not mean to hijack the thread with lug bolts...

I would agree against using grease on the lug bolts for multiple reasons, but we would still use anti seize, which also functions as a lubricant during assembly.

Problem with this tolerance range idea is what kind of range is actually acceptable vs. what range is obtained dry vs lubricated. The measured clamping force in the study showed wildly swinging numbers on dry fasteners, way beyond the observed range of those obtained with lubricated fasteners torqued to the minimum and maximum torque spec range values.

Another facet we have not touched upon is bolt stretching; Porsche uses many single use torque to yield fasteners, and particularly with the clutch and flywheel. None of these fasteners should ever be reused because of the stretch imparted during installation. The flywheel bolts are first torqued to a rather low setting, then stretched by cranking them some additional degrees. As a practical matter, if you have ever done one of these with and without lubricant, you would quickly realize that the dry fasteners are incredibly hard to move to their final position. I have actually watched my techs literally hanging, feet off the floor, on a 40 inch breaker bar trying to achieve the final loading angle, and not getting there on non lubricated bolts. Yet the same tech with the same tool on lubricated flywheel bolts can quickly crank them into their final position without all the fuss and excess force. So I ask you: Which one do you think is installed to the correct bolt stretch, remembering that unlike connecting rod bolts, there is no practical way to measure flywheel bolt actual stretch value? And speaking of rod bolt stretch, running them dry and trying to use the torque spec range as upper and lower limits, it is nearly impossible to get them to the correct measured length, while lubricated bolts will fall into the correct stretch within the torques spec range. Lubrication matters more than you might think...………….

I’m not debating positive effect on lube on accurate torque etc. And my simple answer? If OEM specifies certain torque value based on dry, then I’ll do so without lube and won’t lose sleep over it. If the spec calls for lube then that’s how I do it and again no worries...

I hope you agree potential risk with lube and torque down to the spec. originally meant for dry where clamp force may get close to or exceed yield strength of materials. Do you lube every situation calling for certain torque spec, regardless? Or if the spec is meant for dry you calculate new lubed spec based on frictions etc. (rule of thumb may be 20% less?) to avoid over stressing while improving accuracy/ consistency with lube? I was just making a point not to blindly lube bolts and torque to the spec. without knowing if the spec is actually meant for lubed condition.

With all said, I think OP (or someone here) should confirm if the spec. for flywheel bolts are based on lubed or dry. I checked Bentley and Dempsey’s 101 projects book but did not see lube as procedure.

ARP supplies their own lubricant with the bolts they make & sell.