Drive Shaft. Do they ever get replaced? Or break?

[sugarwood]

A friend's Honda driveshaft sheared today. Just from basic commuting.
How common is it, on any car, for a drive shaft to shear like this?


One guy in the email chain joked that a German version would be 6x the cost.
When trying to price one out, I only found boutiques like SierraM, Paragon, and Vertex selling them.
I think Pelican may also sell them, but it doesn't seem to be a big thing at all.

Then, curious to see where you guys buy a replacement drive shaft,
I searched the forum and found almost no threads on drive shaft replacement at all.
Like almost no one here has ever replaced one in 15 years of the forum. (just CV joints and boots)
What gives?

[Peter Zimmermann]

Porsche axles do not have an intermediate connection like the axle pictured. That said, I've never seen a Porsche axle break, although I've seen CV joints fail, usually because of poor maintenance. Every model that my shop serviced was checked for back and forth motion at every major (15K mile) service. We could tell by the movement when a CV joint needed grease, and we devised a way to use a needle-like tube to introduce grease to each CV joint.

(We made a short piece, maybe 4", of copper tubing with the end hammered almost flat, but leaving a small orifice for grease to pass through, and then curved it to fit against the axle. It's round end attached to our grease gun, and the flattened tip would slide between the axle and the small end of the boot. A few pumps of grease and the boot would start to swell up, which told us it was good to go. If the boot still had a metal clamp we would re-use it. No clamp, no problem; we simply used a high-quality tie rap to seal the boot, and keep the grease inside it).

My shop almost never had to replace a CV joint, and we never saw a broken axle. This in a shop that serviced between 3 and 5 911s every day. It's all about maintenance with Porsches. Sadly, I can't offer info regarding the later 996s and 997s, but I don't think reliability is any less when periodic maintenance is done.

[gtc]

I had to replace a shaft once when the splines on the end developed some rust and spun in the CV.

[Kidasters]

I replaced my half-shafts because my boots were original (from 84), and when I priced out all of the stuff I would need to re-build the CV joints, it was cheaper to buy the 1/2 shafts and just slip them in.

[porsche930dude]

That failure is common on honda and acuras. My neighbor had one break the same way. They get rusty under that rubber dampener and it makes a weak spot. Not common on other vehicles

[ben parrish]

Look at the condition of those boots though...my replacement boots are only 6 years old with less than 20k on them and they look horrible with surface cracks.....those look fantastic on the broken shaft.

[sugarwood]

Peter, can you explain how to check for the back forth motion?
Do you still operate your shop?

[sugarwood]

Originally Posted by Kidasters

I replaced my half-shafts because my boots were original (from 84), and when I priced out all of the stuff I would need to re-build the CV joints, it was cheaper to buy the 1/2 shafts and just slip them in.

Where did you buy it from?

[steely]

I got mine here (of course).

[sugarwood]

Weird, I wasn't able to find any for sale on PP.

[Matt Monson]

See them break all the time on race cars. They break just after the splines end. But these are cars that are lowered which impacts the angle and articulation. Never seen it in a street Porsche. Here's the race solution:
https://swayaway.com/product-category/axles/axle-porsche/

[3rd_gear_Ted]

Digression;
My 911 track car has Ford driveshafts.
Used in Escorts at one time.
They have a thinner tranny drive flange, so I use bolts with nuts on the backside of the 915 drive
Now I have a 3.6L beating on them, so far so good.

[stownsen914]

Originally Posted by 3rd_gear_Ted

Digression;
My 911 track car has Ford driveshafts.
Used in Escorts at one time.
They have a thinner tranny drive flange, so I use bolts with nuts on the backside of the 915 drive
Now I have a 3.6L beating on them, so far so good.

Do share details!

[steely]

Originally Posted by sugarwood

Weird, I wasn't able to find any for sale on PP.

I ordered qty 2 of 911-332-024-15, this is the part number that I have from my notes anyway, and they do seem to be in stock here on PP as"Complete Axle w/two CV Joints - Boots 911, (1985-89)" same PN with an M60 suffix. Lobro by GKN.

I had >115K on the originals and the PO told me he serviced them once before, but since my boots were torn, and the grease was thrown out, I opted to replace rather than start an icky job which might take me forever and reveal hidden damage in the end. I did keep them for someday when I get really ambitious. All req'd bolts came with them as well. I put them on then asked my wrench to double check my torque a couple hundred miles later when I had her in for state inspection - this was 2014.

hth

[3rd_gear_Ted]

Originally Posted by stownsen914

Do share details!

Ford - P/N# 72GG-4635-BA


PS, I also use a Wavetrac LSD (strike two)

Used Pirelli race slicks with Formula Vee tire treatment (strike three, your outta here)

[GH85Carrera]

I have heard of 911s breaking the axle on race cars with huge sticky tires. Usually after going over a curb and getting the tire in the air with the engine on song and then the tire hits the ground.

On a street car it would be a pretty much not gonna happen thing.

At War Bonnet Tech many years ago Porsche AG brought over some real race car parts. They played with a titanium axle design and had one on a table next to a steel one. It was huge difference for the rotational mass. Just too expensive in the gain. The had titanium connecting rods from the car that won at Le Mans.



Some of the door prizes. They kept the drive shaft of titanium and brought it back to Germany.

[Trackrash]

Originally Posted by 3rd_gear_Ted

Ford - P/N# 72GG-4635-BA


PS, I also use a Wavetrac LSD (strike two)

Used Pirelli race slicks with Formula Vee tire treatment (strike three, your outta here)

So, just to be clear, what drive flanges are those? And the Ford CVs match? And the axles are the correct length?

[Matt Monson]

Originally Posted by GH85Carrera

I have heard of 911s breaking the axle on race cars with huge sticky tires. Usually after going over a curb and getting the tire in the air with the engine on song and then the tire hits the ground.

On a street car it would be a pretty much not gonna happen thing.

At War Bonnet Tech many years ago Porsche AG brought over some real race car parts. They played with a titanium axle design and had one on a table next to a steel one. It was huge difference for the rotational mass. Just too expensive in the gain. The had titanium connecting rods from the car that won at Le Mans.



Some of the door prizes. They kept the drive shaft of titanium and brought it back to Germany.

Cool story. Back in the 917 days they had various parts grades. They were generally classified as qualy, sprint, and endurance. They used those Ti axles for short stuff but never in the long races. That grading system was used all over the car with a massive number of components. After they would qualify for LeMans they would strip all the flyweight parts off the car overnight and essential rebuild it for the race itself.

[Peter Zimmermann]

Originally Posted by sugarwood

Peter, can you explain how to check for the back forth motion?

It's pretty easy. With the car on a lift, and the rear wheels hanging free (e. brake off & in neutral), grip the approx mid-point of the axle firmly. Move the axle toward the differential, then back toward the wheel. Do this two or three times. If you can feel/hear the axle bottom out, it'll usually make a thunk noise, that CV joint will need grease (if the axle softly stops, that CV joint has sufficient grease to slow the axle's travel).

Double check your result be squeezing the boot. If the boot pushes easily against the axle inside it, the joint needs grease. As you inject grease (we used Kendall blue grease) into the boot you can actually watch the boot swell up slightly. Don't over-do that, and re-check the axles with the back & forth method in about 5,000 miles.


Do you still operate your shop?

Nope, I sold Red Line Service to Marc Bixen in 1999. Marc is still running the shop, and is in WLA, on Livonia St., just off the 10 freeway at Robertson. Thanks for asking!

...

[3rd_gear_Ted]

Originally Posted by Trackrash

So, just to be clear, what drive flanges are those?


Std 915 drive flange.

And the Ford CVs match? And the axles are the correct length?

Here is the UK source Sierra Rear Drive Shafts | Super 7th Heaven

The size I used was for a Cosworth Escort of the past
It was a plug and play replacement 5 track seasons ago
You can really feel the difference in weight