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Front suspension crossmember - Printable Version

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Front suspension crossmember - patkeefe - 08-19-2012

Hi All:

Car has been a bit rough riding, every bump is transmitted to my hands. Checked the easy stuff, wheel bearings are pretty new all around, ball joints seem OK. Then, today, I noticed that there seem to be two bolts missing on the front crossmember, left (drivers) side. I have never noticed this before, probably because of of the way I jacked the car today was different.



Photos attached. Any opinions?

TIA

Pat

Front suspension crossmember - flash - 08-19-2012

hard to tell what direction we are looking at, but the one in the top shot looks like the crossmember to frame connection. if so, holy crap!

Front suspension crossmember - RS Barn - 08-19-2012

Ditto!!!!

Front suspension crossmember - Cloud9...68 - 08-19-2012

Whoa!! Yep, the bolts that hold your crossmember to your chassis have definitely gone awol. You're very lucky you caught this before disaster struck. So, on the bright side, your problems will be fixed for the cost of a pair of M12 bolts, nuts, and washers. Hopefully you caught it before you started experiencing some weird tire wear, because this surely has been impacting your alignment. But given the the bolts are (I assume) still present and torqued on the passenger side, you may be able to get away without an alignment, although it may not hurt to get one as a precaution.



Weird things like this do happen sometimes. I once discovered totally by accident that one of my rear caliper bolts had worked its way loose, and was probably only a few weeks away from falling out completely. A lesson to us all to take a quick look around anytime we have our cars up on jacks, like during an oil change, brake bleeding session, etc.

Front suspension crossmember - JWahlsten - 08-19-2012

Whoa! Check the the threads on those too. Make sure something bad didn't happen in order to allow them to come loose...

Front suspension crossmember - Cloud9...68 - 08-19-2012

[quote name='JWahlsten' timestamp='1345411156' post='131245']

Whoa! Check the the threads on those too. Make sure something bad didn't happen in order to allow them to come loose...

[/quote]

Doesn't look like there are any bolts left on which to check the threads... <img src="/forum/images/smilies/968/ohmy.png" class="smilie" alt="" />

Front suspension crossmember - patkeefe - 08-19-2012

Thanks, guys! I will try and get some bolts tomorrow. I suspest those have been AWOL for a long time. The 968 is wifey's car, and doesn't get driven much. It's back in the garage resting. Anyone know what bolts those are, spec wise? I can't seem to find my PET Katalog anywhere. Oh, BTW, the bolts ARE in the passenger side, and are pretty tight. The car tracks and brakes pretty straight, so I have no reason to believe the alignment is bad.

Thanks again.

Pat



Edit:

Found a link to the PET...M12x75 bolts.

Front suspension crossmember - Nosferatu - 08-19-2012

M12 x 1.5 x 75

Front suspension crossmember - patkeefe - 08-20-2012

Really amazing what a couple of 12mm bolts will do to improve the ride!

However, I am kicking myself in the butt for not noticing this sooner.

Thanks again!!

Front suspension crossmember - tamathumper - 08-20-2012

I think I see it now, the bottom picture needs to be rotated 90 degrees clockwise. I couldn't figure out what I was looking at for a while! <img src="/forum/images/smilies/968/biggrin.png" class="smilie" alt="" /> Man, that must have made one heck of a CLUNK when you hit a bump!



Glad you got it sorted!



[Image: missing_crossmember_bolt.jpg]

Front suspension crossmember - MB968 - 08-21-2012

Amazing that it could have been driven for any length of time with the crossmember free on one side. Hopefully the threads in the frame are still OK. May need to run a tap through them.



Just in case you've destroyed one of them, I repaired a similar issue some years ago by going to the next larger size inch bolt which was fortunately just a little larger than the existing metric that was stripped. I preferred that over using a helicoil.

Front suspension crossmember - JWahlsten - 08-21-2012

The threads internal to the unibody were the threads I was referring to. Obviously, if you already threaded them in there and torqued them properly, they are okay. You're a lucky man...

Front suspension crossmember - patkeefe - 08-21-2012

Yes, I was lucky all around on this escapade. Luckily, I am a mechanical engineer, and was a machinist when I was in the USAF, so I dealt with a lot of fastener issues.



As much as I hate to even have to bring this up, these two bolts obviously fell out. Bolts don't just fall out if they are installed correctly, and it is safe to say the wifey was not running the Baja 1000 since the last alignment. It has not been on the track since the last alignment. I am ultimately responsible for the safe driving condition of the car (in exchange for cooked food magically appearing before me daily, and clean clothes to wear!)



BTW, I put in grade 8.8 m12x1.5x75 bolts. I don't know the torque specs, but the existing passenger side was at least 90 ft-lb, so I torqued the new ones to that amount. I have no idea what the correct grade bolts and torque for these bolts are. I have no manual for the car (surprise), and there is nothing in my cheap 944 manual.

Front suspension crossmember - mbardeen - 08-21-2012

There are torque specs for the 944 at the Lindsey Racing site. Most of these should be the same as our cars.



http://www.lindseyracing.com/LR/Parts/TORQUESPEC.html

Front suspension crossmember - Cloud9...68 - 08-21-2012

[quote name='mbardeen' timestamp='1345574291' post='131363']

There are torque specs for the 944 at the Lindsey Racing site. Most of these should be the same as our cars.



http://www.lindseyracing.com/LR/Parts/TORQUESPEC.html

[/quote]

That's a handy reference! Thanks. I've spent a lot of time on Lindsey's site, and I've never run across this before.

Front suspension crossmember - MB968 - 08-21-2012

Just put that part of the car together a couple of weeks ago. The 968 manual calls for the "Cross member to body" M 12 at 85Nm/63ftlb.



90 ft/lb is a lot of torque for an M 12, especially for an 8.8. Check some of your engineering refs. (I'm also an ME.) I'd retorque both sides; you don't want to take a chance in stripping out the welded into the frame nuts. If you are concerned, use some removable loctite on them.

Front suspension crossmember - patkeefe - 08-21-2012

Matt, thanks for the reference!

MB, I originally was going to 65 ft-lb on the new bolts. Thanks for the sanity check on this.

When I checked the other side, they were AT LEAST 90. So, I went back and jerked the torque up on the new bolts. I don't think I got them to the plastic range, the 8.8 are supposedly 116 kPSI yield. I am getting new bolts for both sides.



The thing about Porsches is that there are some fasteners which are practically off the chart when it comes to torque values. I am just short of the farmer method here...tighten it until it squeaks, then go another 1/4 turn (which is just like 993 Dilivar head studs, IIRC).