What are the benefits of re drilling 914 4 lug hubs (with mods) to accept 5 lugs...vs using 911 5 lug hubs from the start?

What are the drawbacks?

All opinions welcome

Sean

You cant use early 901 911 5 lug hubs unless you have 914-6 stub axles. You current stub axles will not work with a 911 hub.

Best way to do it is machine out your current hubs or check the resource section for erics hubs. Pretty good bargin.

I use 911 stub axles, and 911 CV joints on my 914-6 axle shafts and 911 coarse spline transmission output flanges.

I can buy new CV joints that are larger/more durable than the originals.

Another option is to use the setup John describes, but with a 911 coarse spline sportomatic transmission flange. It's a little longer than the manual transmission flange. This allows the use of a 911 axle and the 4-bolt CV's.

One consideration is you make the weakest part of the drivetrain your transmission (or tires, depending on width) though. So, dropped clutch starts will result in a blown tranny or tire spin rather than a CV or stub-axle letting go.

I had a stock 914 CV let go on a 2nd-3rd shift this Summer on the way to WCC (last day of a 6 day trip too...). Changed to the 911 setup for piece of mind. I have a 2.7L built to specs in Bruce Anderson's book, so should be good for about 210HP.

Cost. Plug-n-Play.

You can simply replace the hubs on your car with a set that's been drilled to 5-lug (same splines on the stub axle) and you're good to go.

Great,

Thanks for the replies....
I was looking at Erics work (nice stuff) but thought I could use some of my old 911 junk around the garage....

So all I need is 911 hubs, stub axles and CVs and I'm good to go...(thankfully I have most of that kicking around somewhere...)

Well it would be nice if it was that easy.

To use 911 CV's, you need 914-6 axle shafts (same splines as 911 cv joints). Then you machine a lip for the wider 911 CV to fit all the way onto the 914-6 axle shaft and still install the snap ring.

If you only wanted to do one end so that the 914-6 cv joint can still bolt directly up to your transmission, you could do that.

You would need 911 stub axles and cv joints that go with them, and 911 outer hubs. 1971-1973 911 outer hubs are a direct fit. 1974+ 911 rear hubs fit fine if you use 5mm spacers between the bearing and the hub (the 1974+ 911 had 5mm wider rear wheel bearings, and they simply machined the hubs an additional 5mm)

If you went with the redrilled 4-lug hubs, you keep your existing cv joints, axle shafts and stub axles.

Redrilling and studding /4 rear hubs is easier and cheaper. Just be sure you have someone 'in the know' do it. I've seen ones where a DIYer did the redrill and pressed the studs, and they wobble about or can come out by hand. You can always tack the studs in, too.

Alright , to get this straight....

To use 911 stuff the 911 parts list is...
Outer hub, stub axle, cv joints, drive axle and (sportmatic) transmission flange. pretty much a total conversion.

OR...send my current 914 hubs to Eric!!!!

Is there any DISADVANTAGE to the redrilled 914 stuff if done correctly (like Eric does)?

There is a possible strength issue with the hubs. You are drilling them for studs in places that they were never designed to have studs installed. I have not heard of failures of redrilled flanges, but if there is a better alternative, the I would use it.

Personally, I have the 944 turbo stub axles and CV joints on my car. It was a plug and play solution after a little playing around. Big, heavy duty CV joints with 6 bolts to hold them to the flanges.

I added a spacer ring, and used the 914/4 shafts. If you want to use the 944 shafts complete, you have to machine the 911 hubs, removing the amount of the spacer ring from the back side. Then the 944 axles just bolt in!

Absolutely false.

Doubt there's a problem with the 'strength' of the hub. If you're worried of there being too little material for the stud to go through, you can always have the backside welded up around where the studs will go through, machine it, press in your studs and weld the studs in. Seems kind of overkill though.

We weld on a 7mm boss around each hole. This gives the hub the tallest boss (full stud engagement) of any Porsche hub... 11mm.

Overkill. Lifetime guarantee.

Well Eric,

I think I'll be calling you soon....

S.

Cool... not trying to be a pitchman, just want you to be informed.

Mine were just pressed on with the studs! Duh O!


Does that mean I can drop them off and have you weld them up the next time I'm in Utah. (Spring Break! end of March - Here we come!!!) They are still sitting on a shelf waiting to be installed....

Just giving Eric a hard time! Eric's stuff is great!

(Bought calipers, CV's and trailing arms as well!)

Absolutely... box'em up. They have evolved over the last couple-a-years

The disadvantage as I saw it....

At the time 914-4 CV joints were NLA. Since then there are folks redrilling VW CV joints for the roll pins and offering them for sale.

I also feel that the 911 CV joints may be a little stronger. I know I found them cheaper....

I've not heard of a 914 hub failure.

914 CVs can and do fail. In addition to being a wear/maintenance item, they are marginal on high horsepower motors. Never seen a rating - probably would be difficult to quantify. As I said, I had one explode at a very inopportune time and missed WCC, and was stranded on the kitsap peninsula for a day. It's good that the redrilled VW CVs are available, but not using them on my -6.

The next in line to fail is the stock 914 stub axle. There have been a few instances that I know where the stub axle failed on hi-po motors. Again, the 911 solution addresses this failure mode. I imagine this would never be an issue with < 180-200 HP on the street.

Again, with what I have, the tranny is probably the failure mode now, but I don't abuse mine, and have a spare if needed.

YMMV, G.

with both Gary and John.

The fact is, the 914 hub is not an issue. Even the marginal redrill jobs I've seen have never "failed" per se. I've seen a bunch with wobbly studs but no failures.

There is one picture floating around out there but once you see it, you'll know that it was operator error. It was on a hub that was obviously drilled by hand with no spot facing etc.

If you're going to be banging around with a high hp six, driving agressively etc., then 911 or bus CV's would be the ticket (Mike Mueller are you out there? )

Ah, see it's good to ask these questions....
My 914 has a pristine 3.2l carrera motor waiting to be dropped in....

Eric, your hubs seem like the least hassle for a 4 banger....but I am interested in the 944 set up as parts are plentyful and cheap (relatively)! Oh, what to do... what to do?

With a 3.2 your 914 CV's probably wouldn't last too long.

There's plenty of people out there doing it but... I think you're on the right track.

On a side note, we're currently developing a bus axle setup that will bolt right up.

With our 3.2 track car, we used 914-6 axle shafts (bought the complete axles). We only had one CV joint ever make any noise. (That's when I found out they had a different spline count than the 914-4 axles.)

We used the 914 CV joints for probably 6-7 seasons of DE (2 drivers) before we had any failures. Then we started having transmission troubles (not CV joint troubles). When we went to a different transmission, the track car was fitted with 911 Carrera axle shafts (complete with stub axle).

Unless you abuse the 914 CV joints (or don't maintain them), they should last a long time. I think they are strong enough. It's just that the 944 units that can be made to work, or the 911 units that can be made to work are that much less prone to fail.

The bolt-up bus axles would be interesting if the price is right.

I'm just hoping that they don't quit making 911SC CV joints (that's what I use).

just my $0.02

I have a theory John... corect me; I think track CV's would last longer than street. What do you think?

Why?

I wouldn't expect that they wouldn't see the same stress levels on the street as they would be subjected to on the track.

Since track only cars see far fewer hours of operation than do street cars, if the street CV joints would fail before track only CV joints, I would expect that street car CV joints would never last a year.



Eric, please do tell......

As mentioned... just a "personal" theory (and I'm kinda a dumb) but, let's say you've got a 3.2 in a street car, you're probably going to use some of that power you have.

The main thing in my mind is the transition. A street car sees a lot of stops and starts or... on/off transitions. I would be willing to bet a few of those starts may not be "becoming" of a 901 with 914 CV's attached.

A race car would see one (rolling) start and one (regulated, meaning you're noting going to go skidding into the pits) stop and many smooth(er) transitions. Let's say you're coming out of turn 14 at 45mph onto a straight. A CV in motion simply sees more torque applied as it spools up the motion, then more torque applied in the opposite direction as it slows for turn 1. Constantly in motion, it can apply the torque with less stress on the joint.

I would imagine stop-light racing would be worse...

Enlighten me. Maybe it's that torque that kills them...

A track car also has sticky tires, and is applying all the TQ possible every chance it can. a 30 min race is 20 min of HARD acceleration. much full throttle time does a street car see? 5, maybe 10 second bursts? 10 seconds in my car is double the legal limit (or damned close)

BJH