Aluminum Driveshaft
 

I found out my driveshaft has a dying U-joint on my highly modded, tracked MSM. Unfortunately, I heard the U-joint on the OEM part isn't serviceable, so I'm looking at this as a chance to upgrade to a lighter, stronger unit.

I was given a quoted price in the $300 range from one place in Southern California that offers an aluminum piece with serviceable U-joints. Sounds enticing to me, but is there anything I should know before buying such a driveshaft like strength compared to an OEM MSM unit?

That's a more reasonable price than I'd have expected, actually.

I've heard of shops that will rebuild an OEM driveshaft (with serviceable joints) in the $200s, though I couldn't quote an exact price off the top of my head.

Something to consider, anyway. The stock unit is surprisingly lightweight.

stock unit weights like 10-15 lbs man i would take it out and make a few wiegh ins before you make your decission any 1.8 driveshaft will drop right in on your car so a new to you driveshaft can be had for as little as 50 bucks. something to consider imo.

Sounds badass, but honestly how much weight will you be saving? The stock one is VERY light last time I picked it up which is a few weeks ago. If you're rolling in cash go ahead and get the baller aluminum unit. If you're not I'd suggest a stock replacement.

I know the stock unit's pretty light, but if the replacement is close to the price of the Al unit that's lighter and stronger, I'd say why not. However, I'm just concerned of the strength of an Al unit and to see if anyone's had experience with one.

http://miataroadster.com/brands/acpt/acpt_cfds_200.png

only 800 bucks, haha

Never seen aluminum driveshaft failure on a Miata, but it happens quite often on other high power modified cars.

http://ksaiperformance.com/gallery2/...serialNumber=1

http://ksaiperformance.com/gallery2/...serialNumber=1

I would just replace it with another OEM one.

I'm aware of the CF one. Baller piece indeed, but I'll save that for a more crazy build in the future.


Yikes, that looks like that happened at AAA Auto Club Speedway (Fontana, CA), based on the garage the car's in. I can see that happening there on a high HP car.

Having never actually weighed one, I'd still say that the stock 1.8 unit is less than 10 lbs. You can easily pick it up and swing it around with two fingers.

Well, for the reason that Magna points out (good junkyard units are cheap as hell) I'm guessing that there aren't a lot of folks who can actually weigh in here (pun intended) with first-hand experience. Searching turns up nothing...

On the other hand, if someone had experienced a failure with an aluminum unit, I'm sure we'd have heard about it.

On the gripping hand, here is a brand-new steel unit for $197: Car Part Wholesale - Auto Parts and Accessories Catalog - Powertrain Driveshaft For 2004 Mazda Miata

There are other reasons to go with aluminum driveshafts. The harmonics are softer, and that puts a little less stress on the drivetrain.

The MSM driveshaft has replaceable joints. So just replace the joint and be done.

Or replace it with a non-MSM driveshaft. They interchange. The non-MSM shaft does not have user servicable joints (though not intended by mazda, you still can replace u-joints with some work).

There are to many variables to say yes the Aluminum shaft is stronger or not, It depends on the type of Aluminum and wall thickness. It could be stronger or, they could make it out of old soda cans and it would not be stronger. Ask the shop that is making it. I know the shop in my area wont make a shaft unless its stronger than the one its replacing.

Stock unit IS surprisingly light. Every time I have gone to pick one up I have put way too much ass into expecting it to be 25-30lbs, then I find it weighs probably less than a gallon of milk. One of those parts that just weigh much less than they look like they would.

Just for reference...a gallon of milk is just over 8lbs.

IIRC standard 1.8 shaft is 11lbs and MSM shaft is 14lbs

I was under the impression that the stock unit is Al. The whole point of this thread for vagaxt is the fact that this new one would have servicable, removable?, u-joints.

I'm pretty sure it's steel.

The whole point of the thread is he already has serviceable joints.

I'm lost...whatever.

is this the one that will not impale you?

For you, I'd think that would be considered a desirable trait?

That is one of the bad things about either aluminum or steel driveshafts as hustler stated... They do have the capability to punch through the floorpan and hit/impale the occupants in the case of a shear as seen in the photos above. However, when a carbon fiber one breaks/shears like that one it just becomes harmless fibers that cause no additional damage. In saying that, should you buy a carbon fiber one for this safety reason? HELL NO! Will you be putting enough torque on your driveshaft to shear it in normal racing conditions? HELL NO! So I would not worry about this unless you expect either your transmission or rear end to complete lock up while at high speed. But I would just replace the U-joints since they are servicable on your driveshaft.... Just my $0.02.

Ive only seen them do this while launching at the drags.

I just weighed my spare and it indeed is 11lbs.

My memory is good to the best I can remember.

Exactly my point...

This is why you weld in driveshaft hoops around the shaft. So that it can not do that.

Indeed. However, there are a lot of budget builders who take their cars out to the track and fully overlook this and the results can be devastating... Well at least I've seen three at a local drag strip break their driveshafts and have them punch through the floorpan. Not pretty... All were un-injured though.

I thought that too, but that's definitely one of the garages at ACS Roval, and those are R888s on that car.

I thought the more common accidents with driveshafts, are when they break and impale the ground. This can make the car flip over. Not pretty. Do they not tech cars for driveline loops in road racing? They sure as hell do in drag racing.

From what I gather so far, the Al replacement is around 7-8lbs and OEM steel replacement is about 11-12lbs. I'm still taking in more opinions and time before I settle on a replacement. So far, I'm leaning towards the steel replacement or finding a used OEM shaft. IMO, MOI for the weight difference on such a small radius wouldn't provide much in performance gains.

I would estimate that the "gains" would not be measurable on a dyno, or in any datalogs of acceleration.

Every pound counts, especially rotating mass.

Has anyone seen aluminum driveshafts impale/flip cars, or just steel units?

I had alu drive shaft on my previous car, s13. it is quite noticeably different from stock but I dotn think i would bother with one from now on, seems a bit unnecessary spending

Road racing isn't typically as harsh on drive line components, standing starts are not common.

Some classes do have a safety requirement for a driveshaft loop, and those classes are very much tech'd for it.

HPDE, or track days do not have such a requirement.

Has anyone seen any driveshaft flip a car?

I have never seen it, just heard of it. However, I have noticed a certain amount of horseshit from hot rodders. Maybe a myth?

Research edit: MYTH BUSTED!

Mythbuster apparently tried this... Link to results: http://www.mythbustersfanclub.com/mb...nt/view/52/27/

Cliffnotes: The car would jump up off the ground slightly but never flip. All adding speed accomplished was to shove the driveshaft further into the trunk... MYTH BUSTED!