CV joint bolts/screws

[TX911SC]

I replaced my CV joints last week and wanted to share an issue I had with bolt length. BTW I replaced all 4 of the old CV joints with new Loebro axle/CV joint complete units. All 4 of the old CV joints were installed with 50mm bolts (not by me). So, I installed the new Loebro units using new 1.25x50mm bolts. The 50mm bolts on the inboard CV joints (at transmission flange) were perfect (i.e. they extended beyond the flange by about 2½ threads. However, on the outboard CV joints (at the hubs), the 50mm bolts were too long. When fully torqued (34 lb-ft per Wayne's book), they locked the hub up. In other words, I couldn’t turn the hub. I couldn’t see the backside of the CV joint, but the bolts were clearly keeping the axle from turning. To confirm it was a bolt length issue, I backed them off a few turns and all was okay. My solution was to install 1.25x45mm bolts and the axles/hubs turn fine now. So I now have 50mm bolts on the inboard CVs and 45mm bolts on the outboard CVs. BTW, this is an ’83SC and there were no retainer clips or washers on the old CVs. I did not install retainer clips, but I did buy and install Schnorr washers for the new CVs. Just looking for your input and wondering if anyone else has experienced this. As always, thanks.

[Jdub]

No, I have not experienced this, but you took the right road on your fix. The extended threads will cause no issues as far as I can see.

Do this: When you go to retorque (and you MUST do this) have a bottle of white and red paint from the local hobby store at hand. As you retorque each inner, dab white paint on the bolt where it sits against the surface. Use the red paint for your hub-side. This way you can check for backing off (hairline crack in the paint between surface and bolt) and also know which bolts are what length.

I know, kinda ADD, but I *do* use paint dabs to track any bolt loosening. It is a small effort for a greater benefit.

[L8apex32]

I think what you found is normal and expected. The inner bolts are longer than the outer ones and you can't use inner bolts for the outer side.

I munged the threads on my inner side recently (one hole), probably due to re-using a dirty bolt (sand, grime, etc). FYI

[gtc]

The same thing happened to me a while back. I just ground a millimeter or two off the end of the bolts with a bench grinder.
I couldn't see how many threads were exposed, so using 5mm shorter bolts seemed risky to me.

[TX911SC]

Originally Posted by Jdub

No, I have not experienced this, but you took the right road on your fix. The extended threads will cause no issues as far as I can see.

Do this: When you go to retorque (and you MUST do this) have a bottle of white and red paint from the local hobby store at hand. As you retorque each inner, dab white paint on the bolt where it sits against the surface. Use the red paint for your hub-side. This way you can check for backing off (hairline crack in the paint between surface and bolt) and also know which bolts are what length.

I know, kinda ADD, but I *do* use paint dabs to track any bolt loosening. It is a small effort for a greater benefit.

Thanks Jdub. ADD? Not at all. I used my wife's nail polish to do exactly that.

[TX911SC]

Originally Posted by gtc

The same thing happened to me a while back. I just ground a millimeter or two off the end of the bolts with a bench grinder.
I couldn't see how many threads were exposed, so using 5mm shorter bolts seemed risky to me.

Yes that kind of worries me. I know that 50mm screws were too long. Hoping the 45s are okay. Wish I could see the backside like on the inboard flange.

[Lukesportsman]

OK, so I guess the CV's have been redesigned requiring shorter bolts. I've seen where 47mm is considered "ideal".

The axles I just received indicated that 986 332 190 00 were the bolts to run. These came out to be Boxster bolts and in my best thoughts are NOT the ones to get. $66 bolts to return as the step doesn't go through the SC/Carrera CV joints. So, thought likely the right length, they don't seem to be solution. They are shown to be grade 12.9 so I guess Porsche tends to prefer hardened bolts here!

ANYONE have FEEDBACK or OPINIONS on what is best here?


Quote from axle manufactor " New Design Axle Flange **6)986 332 190 00 8X45mm CV Bolts Required per Axle** (100mm Inner Joint) GKN/Lobro has changed the design of the axle flange to be 5mm thinner. (Standard CV Bolts are 5mm too long)."

[ClickClickBoom]

Try the Reconstructing CV thread. A big pile of posts!

[47silver]

I have experienced this problem. The bolts are supposed to be 48 mm. I would not feel comfortable with 45 mm bolts. Have the 50mm cut to 48 by a machinist

[Discseven]

I used longer bolts to consume all CV threads in the Host CVs I got. Left bolt below is the spec'd 50mm. Next to it is the 55mm (class 12.9) I used. Lock washers with these only --- no double hole "C" washers used.

[Lukesportsman]

I like Disceven's solution of using a lock washer to resolve the 2.5mm difference between new/old CV joints. I'll obviously confirm visually after attempt.

[ClickClickBoom]

I hope that either a Schnorr or Nord-lock washer vs a split washer was used.

[JJ 911SC]

Originally Posted by ClickClickBoom

I hope that either a Schnorr or Nord-lock washer vs a split washer was used.

+1 on that...

[TX911SC]

I used 50mm bolts on inner cv joints and 45mm bolts on outer cv joints...and Schnorr washers on all (the old cv joints used 50mm bolts on all 4 cv joints with NO washers whatsoever). I am perfectly comfortable with the 50mm bolts on the inner cv as I can see that they extend 2.5 threads beyond the flange. I am only semi-comfortable with the 45mm bolts on the outer cv joints as I CANNOT see if there are any excess threads (as on the outer side). I've put about 1,500 miles on the new cv joints and re-torqued them once.....so I'm getting more comfortable with the 45mm bolts. Next time I will go the route of grinding a couple of millimeters off the 50mm bolts for use on the outer cv joints....or until they don't interfere with the free-turning hub. There should be a more exact fix.

[JJ 911SC]

Yes the outer one is kind of going blind.

I did some measurement and will be double checking them tomorrow (installing an axle) and will post but IIRCC the spacing on the "outer flush" and locking the wheel is 3mm.

Sticking out only give you a good feeling but does nothing mechanically.

If the 50 on the outer jam the wheel, 45 is 2mm short of flush.

Funny enough for the axle I got from Lobro (via PP) does mentioned that YOU MUST USE the supplied 47mm, which would be in line with the above calculation except God knows where they get a 47mm measurement out the stud they supplied...

[TX911SC]

JJ,

Right! The bolts supplied with my Lobro axles were 45mm also (44.7) and I wound up using them on the outboard sides since 50mm bolts locked the wheel up. So, I think you & I had the same experience/results. And again, so far the 45mm are working. Checked them today when I did a valve adjustment and they haven't moved.