I'm a Torx head noob, so to speak. I say that because I've never had so much trouble applying proper torque to any other bolt on the car and, I'm a bit frustrated. Having to do this while laying on my back hasn't helped either.

I understand why Nissan chose Torx head bolts to secure the flywheel though. They produce 0 cam-out forces, they are very hard to strip and, they require almost 0 normal force to take driving torque.

That's lovely and all but, the head design allows for significant lateral play when the socket is inserted (yes, I used the correct size: T55), unlike its Hex and Allen head counterparts (generally speaking). In combination with my hamfistedness, I've done a bit of damage to 3 of the 8 flywheel bolts on my car. The bolts heads are still intact enough to remove but, I'm not confident the applied torque is the required 93ft-lbs (I know that is higher than stock but, the flywheel is aluminum. See here for the spec). I stopped torquing before the wrench clicked when tightening those 3 bolts because I'm afraid of complete stripping the bolts. The bolts are damn tight but, I'm still a bit afraid that the flywheel will warp.

Anyway, I'm wondering what you more experienced mechanics do when it comes time to torque a torx bolt while under the car? It's very difficult to keep the torx bit true while tightening to such a high torque level. I was considering just using a torque stick and my impact for a while but, I'm not confident that's the best idea.

 

Torque stick is definitely not the way to go. What brand of torx sockets are you using?

 

At first I used a lisle socket, which I shattered after 5 minutes of use. I then went out and got a craftsman socket which is about 2 inches long, 3/8" drive.

 

I used brand new bolts when putting mine back on due to rounding some of the corners on the heads. When torquing them back down, use some valve-grinding compound to your bit to add a little friction(easy to clean up afterwards). It really helps. I also had to brace myself against something stationary since I don't have a lift. You'll find out that you need as much force pushing into the bolt as you do twisting it. Anyway, I got mine to torque. Just be patient. If you need to know anything more specific, feel free to ask.

 

Well, I wouldn't mind knowing why this design is used when there are other drive designs that are equally as strong, produce no cam-out forces and have less lateral play. I'm seriously thinking of replacing these stupid screws with a different drive design when the flywheel comes out next time.

 

This. Take your time and put a LOT of force down on the bolt. Strain yourself and take breaks between if you have to, it's worth it over stripping the bolts out.

 

Unfortunately bolts heads that don't have much head clearance and therefore require internal wrenching (flat heads) and have a fairly high torque spec. can be a pita.......just a fact of life. Internal torx are about as good as you can get, but as mentioned above you have got to apply a good "down force" and keep square, as you've found out. I'm not sure what you think might be better. Tri-wing, Pozi, High Torque, Phillips and Robertson will not work with the torque requirement that you're talking about. My '81 VW used some AZN (I think it was called) which uses a tapered fine spline looking adaptor which did "wedge in" quite well and didn't seem to cam-out easily, but I doubt that it was used for any really high torque hardware. There is "Spline" which I've used and it is used for high strength, high torque hardware where you will break your wrench or socket before it loses it's grip. We only had external spline nuts and bolt heads but I think I've seen internal flat headed Spline bolts somewhere.

 

Pics of said bolts?
I'd never done a clutch in a 5+ gen so I'm curious what you're having to deal with...
Would it be possible to use a flywheel bolt from a 4 gen or earlier?
the 3 gen uses a standard hex head bolt that's not very deep and has an oversized, flanged head..
best pics I could find of the bolts...
http://blehmco.com/pics/car/drivetra...h/MVC-012S.JPG
http://blehmco.com/pics/car/drivetra...h/MVC-015S.JPG

 

Hey, Matt. It's a simple internal socket head torx. T-55. The stock flywheel is a dual mass and you can't use a hex-head bolt because it's got a recessed flange, unless you remove material. No thank you. I have pics somewhere, but I don't have them hosted. I might get around to it tomorrow if no one else posts.

OP - I imagine any internal socket head will work, but I don't imagine any design will decrease the tendency for the socket to 'walk' out of the screw. The 'Z-axis' is not biased one way or another.

 

How about a regular allen key instead of a T55? part of the problem is the T-sockets are tapered toward the end, so on high torque they tend to push out. on an allen key, they don't.

So it sounds like the issue with these is head diameter, not head height?
how about these? I think the VG/VE bolts are 12mm x 1.0mm...
http://metricmcc.com/catalog/Ch1/1-43.pdf

 

Yeah, I had the same idea, but I couldn't source any locally. Besides, my Audi has the allen key cap screws and they're no better. They round off, too.

 

DO NOT, I repeat, DO NOT substitute the bolts with any that are not designed for the purpose of attaching the flywheel to the crank. Using bolts of unknown material and/or diminsionally different (shank dia. and grip/shoulder length etc.) from the correct/approved bolts is just asking for trouble. You are also adding about 50% to the standard torque value of the stock bolts for the stock flywheel because of the Al flywheel........so I hope that you are using the correct bolts.

 

I understand the issues with substituting one bolt for another. I was merely throwing the idea around.

As for the torque, A T55 Torx bolt can withstand approximately twice the torque I was applying before failing. A safety factor of 2 is pretty good.

 

After finally getting everything torqued properly, I'm going to have to take the flywheel off because the threads in one of the bolt holes for the pressure plate is damaged. Great.

 

The bolt has to also withstand the loads applied to it during engine operation......not just the load applied to it when you torque it. Don't forget that you are stretching the bolt a few thou when you apply that 90 ft/lbs torque to it, which is simply supplying the clamping force. Is this a Nissan flywheel or an aftermarket?

 

I'm not an engine designer (yet?) but, the mechanical loads on those bolts should be limited to axial tension only. Of course, there is the thermal cycling due to engine and clutch heat. But, that is another story. I'm not actually going to replace the bolts with something else. There are too many variables to take into account for me to feel confident.

The flywheel is a Fidanza Aluminum unit.

 

Ahh... the VAG "triple square". Held the axles to the trans on my Audi's. Bucket loads of torque to break loose.....I swear i thought I snapped something.....like the breaker bar! when removing them...yet after the big kaBANG of breaking them loose, they came out with fingertips.

I don't miss wrenching on German cars at all.

 

Why do aluminum flywheels need the bolts torqued higher? The sheet that came with my Fidanza said to torque them to oem spec (69ft-lbs)..

 

Try clicking http://www.fidanza.com/FAQ.aspx there for the spec.

4. WHAT TORQUE SHOULD I USE TO TIGHTEN MY NEW FLYWHEEL? – For both the clutch and flywheel mounting bolts you should follow the original manufacturers torque specs for your car. We do recommend using a small amount of semi-permanent Loctite on the flywheel mounting bolts. We also recommend replacing both sets of bolts. These can be gotten from your local dealer or from a company such as ARP Fasteners.

"Semi permanent Loctite" I would take to mean Blue. Red Loctite is generally considered permanent.

Cheers.

 

I'll follow these specs next time. Tightening the bolts to 69 ft-lbs would have been so much easier.

 

and the torque (circumferential shear) you are tightening them to.....

 

Ah, yes. Torsion. Thanks.