Cv conversion

Since U-joint flanges have a different bolt pattern than CV joint flanges, the inexpensive kits use an adapter at each end. The more expensive kits include CV output shafts for your ZF and CV companion flanges for your stub axles, so no adapters are required.

Ya I realize that, but at more then tripple the cost, even if each output/axle end cost $500 to make there's a BIG difference in cost.

That price from SACC is per axle I presume.

Are you referring to the Mark Williams kit? I believe it comes with stub axles too, for the "over $4,000" price tag. There are other potential differences that can drastically affect the price. Examples are 300M vs 4340 (or 4130) shafts, strengthened vs standard CV joints, aero vs standard bellows style CV boots, etc., etc.

quote:

Originally posted by Hemihunter:
That price from SACC is per axle I presume.

Well heck idk, it didn't really say in the description.

quote:

Originally posted by Hemihunter:
That price from SACC is per axle I presume.

No that's for the pair. I purchased a couple sets of these last time Scott had them on sale. Yes there are more elaborate solutions at higher cost that involve changing stub axles, but as a bolt on upgrade from the stock half shafts I think these CV axles are an inexpensive solution for the average street driven Pantera.

Also available as a self assembly kit if you have a bit of time and want to save a further couple hundred bucks.

Julian

Thanks Julian,
That's what I wanted to hear, were there any issues with installation, or running?
Thanks Joe

I have CV axles on my car. I did the conversion years ago along with the nut and bolt restoration. SACC did not have a kit on the market at that time and the rest of the vendors that had it were IMO way too costly. I used our Maserati Bora as an example and found that Maserati used the adapters to convert the four bolt ZF axle stubs to the CV joint bolts. I figured if the Bora has them they must be ok. We decided to construct our own kit. We turned 4 adapters on the lathe. The axles and the 930 CV joints were purchased from our local Dune Buggy shop. To make a long story short they work great with no issues what so ever. If I had it to do over again I would simply purchase Scott's kit as the final cost was only $200 less for making it myself. BTW turning the adapters took three full work days to complete. turning them down then tapping all the threads etc.

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To make a long story short they work great with no issues what so ever.

Exactly my experience with the "old-school" Spicer aftermarket upgrade that uses standard u-joints.

Larry

quote:

Originally posted by LF - TP 2511:

quote:

To make a long story short they work great with no issues what so ever.

Exactly my experience with the "old-school" Spicer aftermarket upgrade that uses standard u-joints.

Larry

I think the misnomer here is that the Spicer halfshafts are an 'upgrade'. It was at one time cheaper to purchase Spicer half shafts than the replacement u-joints for stock half shafts. The latter is now readily available and the stock half shafts are as equally capable as the Spicer ones IMO.

If you've seen a car where the u-joint has let go it does some major damage to the rear inner fender.

Julian

quote:

I think the misnomer here is that the Spicer halfshafts are an 'upgrade'. It was at one time cheaper to purchase Spicer half shafts than the replacement u-joints for stock half shafts. The latter is now readily available and the stock half shafts are as equally capable as the Spicer ones IMO.

Agree 100% with all of that, Joules.

But u-joint failures seldom come out of nowhere.

U-joints should be checked each year. Are all the retaining clips still in place? Is the u-joint cap a bit shiny? That probably means it is rotating underneath the retaining clip, being polished by the movement. Time to R&R. If your joints have zerk fittings, they should be greased. Yes, I know that is soon followed by excess grease being flung around the engine compartment. Some owners "solve" that problem by mounting the curved SS sheetmetal guards that cover the inboard joints. Which captures the grease, but makes visual inspection of those inboard joints a bit more difficult.

My last u-joint replacement used Spicer joints that do not have a zerk fitting. I spent time talking with the counter rep at a major driveshaft fabrication/repair shop and he said these come fully greased, have a stronger rubber cup so it deflects less (to prevent grease loss) and can last many years on an in-the-weather farming irrigation pump drive. He went on to say that such a long pump-drive life expectancy should translate to more hours than any Pantera is going to be subjected to in 5-10 years, and given how few miles most owners drive each year...... maybe 10-20 years.

Yes, u-joint failure can work like a medieval flail on inner wheel wells....... if the owner has failed to properly maintain his car.

Nothing wrong with CV conversions.

Also nothing wrong with stock, or Spicer, u-joints.

I just don't think the fear of an owner-induced u-joint failure scenario is a good argument for a CV conversion.

Larry

In my case the half shafts needed to be replaced as part of the restoration. I also liked the advantage of not slinging grease. It made sense for me to install CV axles instead of purchasing or re-building the half shafts.

There's also the issue of speed changes of half shafts through their arch of travel, cv's are better in this respect also..

quote:

Originally posted by LF - TP 2511:

Agree 100% with all of that, Joules.

Larry

That's as far as I read before falling off my chair, we agree on something after all these years

I switched from newly rebuild and balanced stock halfshafts to a set Scott's CV axles and the CV axles have a much smoother feel.

U-joints have three characteristics that must be accounted for when an engineer is using them.

First, drive shafts and half shafts equipped with u-joints must be set-up in the vehicle to operate with a small constant angle in order to prevent driveline vibration and to improve the life of the u-joint. Achieving this "small constant angle" is accomplished with independent rear suspension having "half shafts" by off-setting the axial alignment between the differential or transaxle (gearbox) output shafts and the rear wheel stub-axles. The radial axis of the two components connected by the half shafts must remain parallel to each other, but off-set. The amount of axial off-set between the two components connected by the half shafts is critical in order for the u-joints to operate within the acceptable range of angles; that acceptable range is ½° to 3-½° (nominally 2°). The reason u-joints must be set-up with at least ½° of operating angle is because u-joints require some angle or “movement” to minimize wear on the needle bearings. Excessive wear leads to a type of bearing damage known as “brinelling”. This angle appears to have been built into the Pantera chassis by mounting the ZF gearbox slightly rearward in relation to the stub axles. Thus the half shafts operate at a small constant horizontal angle.

Secondly, there is a maximum limit to the amount of angle that a u-joint" should operate at. Exceeding this limit places undue stress on the u-joints, and the bearings that support the gearbox output shafts and stub axles. When the Pantera's suspension deflects upward, such as when it encounters bumps in the road, the vertical angle of the half shafts increases. During extreme deflections (large bumps) the short length of the half shafts causes the u-joints to operate at extreme angles exceeding the prudent limits to their operation. This increases the stress upon the u-joints and stub axle bearings from time to time.

Lastly, and most significantly, the u-joints at either end of a driveshaft or half shaft should not have operating angles differing by more than ½° from each other. A difference in operating angle greater than ½° tries to make the tires speed-up and slow-down during each rotation; the tires don't want to rotate at a constant speed. But of course due to the traction of the tires and the inertia of the moving vehicle this can't happen, so the parts bind, bend and deflect. This is all happening at the "output end", i.e. at the stub axles. The result is harmonic vibration AND severe stress upon the u-joints and stub axle bearings. This is where two problems arise in independent rear suspension applications. (1) Any amount of rear wheel toe shall horizontally misalign the axis of the differential/gearbox output shafts and the stub axles. Any amount of rear wheel camber shall vertically misalign the axis of the differential/gearbox output shafts and the stub axles. Yet for best tire performance the rear wheels must be adjusted for a small amount of both toe and camber. The misalignment on the horizontal and vertical planes combine to change the angle of the u-joints at the stub axles in relation to the angle of the u-joints at the output shafts of the differential/gearbox. (2) As the rear suspension travels up and down the rear wheel camber changes significantly thus increasing the vertical misalignment between the axis of the differential/gearbox output shafts and the stub axles. This is where the stress upon the u-joints and stub axle bearings is most severe, and it is why the Pantera's stub axle (rear wheel) bearings wear as fast as they do. This is also why CV joints make the vehicle operate so much smoother.

CV joints would have been a better choice in this application because (1) CV joints are designed to operate at more extreme angles AND (2) they are designed to cope with differing angles at either end of the same shaft. The Maserati Bora (1971 – 1978), a mid-engine sports car closely related to the Pantera, was equipped with CV joints. The half shafts installed in the last version of the Pantera (i.e. the Pantera Si) were also equipped with CV joints.

If its in the budget a CV joint conversion is a wonderful improvement for a "driver" Pantera or a Pantera race car. It is the "real fix" for the fast wearing rear wheel bearings.

George, I appreciate the insightful response. Didn't know all that!

I can attest to the damage from a broken half shaft, I had just come off the Tehachpi pass at over a 100, got gas in Bakersfield, took off and hit second and WAM!!!
I switched to C.V. joints and never looked back, smooth as silk and pretty to!

No vibrations.

Thanks for everybody's input I'm sold.....

What torque numbers would be used when torquing cv bolts and zf axle flange bolts to adapters?
Bolts are 12 points delivered by Sacc

would those bolts be 7/16-20?
any "grade" stamping on the heads?

They're probably 3/8"-24. The torque spec I use for my 10mm (grade 12.9) bolts is 60 ft/lbs. That's what Porsche recommends for 930 CV joint bolts, which is the OE application for the CV joints we all use.

Bolts are stamped ALLOY FMI and they are 3/8 unf

The torque for the 7/16-20 bolts that hold the adaptor to the ZF flange and the adaptor to the stub axle flange are 80 ft/lbs. Since it is almost impossible to get a torque wrench on those bolts, tighten with a boxed end wrench and an extension very tight. Also use a drop of lock-tight on each bolt.

The torque for the 3/8-24 bolts is 45 ft/lbs. Those are the bolts that hold the CV to the adaptors. We also use a drop of lock-tight on each bolt.

quote:

Originally posted by ZR1 Pantera:
We also use a drop of lock-tight on each bolt.

Do you use red Lock-Tight or some other color?

Thank you for the help!

So Porsche recommends using SAE threaded bolts in 930 CV joints? Is there hope for us non-metric-system hold-outs?

quote:

So Porsche recommends using SAE threaded bolts in 930 CV joints?

No, The stock 930CV bolt on the porsche is a 10mm bolt. A Grade 12.9 10mm bolt is torqued to 60lbs.

Most CV conversion use 3/8-24 bolts. Those bolts get torqued to 45lbs.

Porsche 930 CV joints are found on independent suspension axles. They measure about 108mm in diameter, 40mm thick, and have a 28 spline center. This CV Joint Originally came stock on a Porsche 911 Turbo from 1975 to 1989. The Porsche 911 Turbo is better known in the community as the Porsche 930. Porsche 930 CV's were originally used in the off-road community because they were larger in diameter than beetle or bus CV joints. Since Porsche 930 CV's are larger in diameter they support more horsepower and allow for more angle on the axle. The Porsche 930 cv has a static torque rating of approximately 2,729 foot pounds. More angle translates into more off road suspension wheel travel but CV’s lose 30 percent of torque rating at angles over 22 degrees. To compensate the off road community went to 934 cv joints with almost double the torque rating. The Porsche 930 CV joint was designed for a 10mm bolt. The 10mm bolt is slightly larger than the 3/8-24 at 0.3937 Dia., and a slightly higher tensile strength (150,800 vs 150,000 psi for a class 10.9 or grade 8 bar with a 1 inch cross sectional area). A 3/8-24 bolt has a cross sectional area of 0.0875. Class 12.9 has a tensile strength of 170,000 psi, same as ARP stainless 300 and requires more torque. In the off-road community everyone typically uses an American 3/8-24 bolt because they have greater availability and less cost in the bolts above grade 8. The 930 CV joints generally range from stock GKN German, to EMPI Chinese, to American Pro-Am and Kartek fully race CV joints

Thanks brother-bee.

Good info

Larry

At 20 hrs into the Daytona 24 hr race run yesterday, Corvette lost one car out of the pair (then running 1-2 in class) in the event due to a seized CV joint. One graphic shot showed the affected (brand-new) half-shaft laying on the Daytona garage floor, smoke from burning and boiling grease still coming off, as the mechanics swapped another new axle in place. Lost two laps doing the work.

And speaking of fixing things, the new Ford GT lost BOTH their cars in class at only about 4 hrs into the event, due NOT to engine, halfshafts or transaxle problems, but to seized paddle-shift actuators, after running as high as 3rd overall. Not being able to shift left their manual 6-speeds locked in high gear. The two Ford GTs eventually regained 6th and 10th places in GTLM after being repaired, many laps down. LeMans is coming up for both the 'Vettes and the Ford GTs....