Installing EMPI Half Shafts - What do I need?

[BoostBuggy]

My pr of EMPI 90-6805 half shafts (w/CV's) just arrived. What do I need to install these things? Should I be replacing the CV bolts or can I simply reuse what's on the car?

Don't want to dig into this project and realize there's something else I need.

Furthermore, in reviewing Clark's Garage for removal/installation of CV/Half Shafts, it appears (and feel free to correct me if/where I'm incorrect) that for the EMPI pieces install, as the CV's are already installed and greased, this should be a fairly simple "remove the old and replace with the new" process. I have all the tools Clark's says I need so the only question is that of the bolts. i.e. Should they be replaced with new rather than reusing the old?

Or am I completely missing something REALLY important?

Thoughts/Comments?

TIA

Michael

[Jrboulder]

You don't need to replace them but I like to if they haven't been changed over to Allen head bolts.

[sausagehacker]

Part # N-911-082-01-M36, Pelican has then for $1.00 each, so that's $24 + tax + shipping to replace them all.

Pelican Parts - Product Information: N-911-082-01-M36

If your old ones are fine (you've already taken them out and know they are not stripped), it's certainly fine to re-use them. But when they're so cheap, and the 12-point head gets slightly deformed every time it's torqued, I would recommend you get new ones just so you know everything is square. I used the exact same ones as the above link on my 944 and zero problems.

Jrboulder brings up a good point about these CV bolts, which is that you can replace them allen or traditional hex-head bolts. The 12-point (triplesquare) strips relatively easily if you don't pick out all the grime from them, which keeps the bit from seating all the way.

If you haven't taken the old bolts off yet, I would order new ones just so you have good ones to put back onto the car - you may strip one or two and then you'll be stuck waiting 2-3 days to finish the job while replacements are shipped.

[BoostBuggy]

PP list them as being 8 x 48. Anyone know what the thread pitch is?

I'll probably replace them. But if I know the tread pitch I can pick them up around here, most likely.

[ernie9944]

Buy the one from Ideola's Garage: Products & Parts for Porsches see pics, and you'll never have to look back and worry about your CV shafts bolts coming loose again.

[BoostBuggy]

That may well be but if they haven't come out on their own in 243k miles, what do you think the possibility of new standard bolts, torqued to spec, coming out?

While I'm not suggesting the Stage8 locking bolts are a good idea, they're a LOT more $$ and I've never heard of anyone here or on RL having an issue with CV bolts backing out.

[sausagehacker]

I've heard of them backing out, but if they are torqued to spec there shouldn't be a problem. Make sure they aren't covered in CV grease when they go in (and obviously, pack the CV axles with new grease WYIT)

[BoostBuggy]

The EMPI assemblies come completely greased and ready to install. So no messy grease packing. The pair with shipping (from *********.com) was only $115! Here's the link http://www.*********.com/qgvcvhz-volkswagen-vanagon-axle-assembly.html

BTW Autopliticy.com has them for a couple of $$ less.

[Jrboulder]

The thread pitch is 1.25.

The problem that arises is that torque is a terrible measurement of preload. A bolt (or in this case a screw) is just a spring and the more you stretch it the more clamping force it exerts (to a point). In a shear-loaded joint like the CV-to-axle the force is primarily conveyed by the friction between the two surfaces. This obviously requires a high clamping force (preload/bolt stretch). Unfortunately a torque wrench is only good to+- 25% accuracy in terms of preload so often that can end up as under clamped joint and that's obviously the first step towards the joint loosening. On the other hand, if a fastener is significantly over torqued it will go from the elastic region to plastic where is will not return to its original length or clamping potential and then when removed and reinstalled it will either break on installation or not clamp very well and back out.

[tchudy]

Will the EMPI 90-6805 half shafts fit my 1986 944T?

[BoostBuggy]

@tchudy - That's my understanding from what I have read on RL. As I have a pair and and gearing up to install them I certainly hope that is the case. One poster on RL did mention the EMPI's are a tad longer than the stock ones but he said they do fit. That's all I know so far. Will certainly know much more after I do the job.

@Jrboulder - Thanks for the confirmation on the tread pitch. I had been able to deduce that from looking at the Stage8 locking bolts suggested. Don't think I'm going to go for the locking bolts as I don't think their really necessary but I am going to replace the old bolts with new.

Also nice bit on torque measurement et al

[Jfrahm]

If you go with hex heads you can use safety wire star washers or bendable washers to lock the bolts. For some reason these bolts can back out after axle replacement. It has never happened to me but it seems to happen to others. Cleaning the grease out of the threads and using loctite would be the minimum.

[Lapkritis]

Not sure if you guys have figured it out yet... EMPI uses inferior rubber on their newest CV boots. 12months, 5k miles and they'll be leaking. I have more than 1 car in this state now as a result of going with EMPI. The only remedy is to live with grease flinging long enough for the axle to eventually fail and then get a replacement if it's still in warranty. Better with 20yr old OEM rubber that's cleaned up.

[DannoXYZ]

Adding to Jrboulder's comment on pre-load, thread-friction has a great effect on the torque-reading. For the exact same pre-load stretch, you can get torque variations of +/-25% or more depending upon the following variables:

1. new versus worn threads on bolt
2. dry versus oiled threads
3. oiled versus dirty, greasy threads

One of my friends runs a maintenance operation at the S.B. airport. He says not a single bolt on a plane goes in dry due to #1 above. For example, if you take a brand-new bolt and tighten it to a certain torque then measure the stretch. Then remove it and re-install to the exact same torque, the stretch will be different. That's because the friction on the threads of a brand-new bolt will be higher than a used bolt.

So every single bolt has a specified lube or locking-compound specified, in addition to the torque and/or preload-stretch. I've found using machine-oil on cleaned threads gives the most consistent and repeatable correlation between torque & preload-stretch. That's because it removes the friction from the threads and the resistance you feel on the torque-wrench is actual stretch of the bolt. A dial-type torque-wrench is also much better since it will show the amount of torque-creep you have; especially on high-torque bolts.

Also don't forget to completely clean the mating surfaces between the axle-ends and transmission/hub-mounts. There's no interlocking connection there, ALL the torque is transmitted through friction. For any given amount of clamping-force from the bolts, if you've got any oil or grease in between, it will severely reduce the amount of friction between the two surfaces.

For easy of maintenance and peace of mind, I replace the cheeseheads with allen-socket bolts and drill them for safety wire.

[DannoXYZ]

Originally Posted by Lapkritis

Not sure if you guys have figured it out yet... EMPI uses inferior rubber on their newest CV boots. 12months, 5k miles and they'll be leaking. I have more than 1 car in this state now as a result of going with EMPI. The only remedy is to live with grease flinging long enough for the axle to eventually fail and then get a replacement if it's still in warranty. Better with 20yr old OEM rubber that's cleaned up.

What material is used on the EMPI CV boots? Butyl rubber? Neoprene? Viton? Silicone?