Stock driveshaft weight, and the benefits of aluminum
03-02-2011, 03:22 AM
#1
Stock driveshaft weight, and the benefits of aluminum
What is the stock weight for an NA driveshaft? Has anyone here had a custom lighter one made?
What kind of reduction in drivetrain loss can be had with say... even just 5lbs shaved off the driveshaft? Just for example.
What kind of reduction in drivetrain loss can be had with say... even just 5lbs shaved off the driveshaft? Just for example.
Reply
0
0
03-02-2011, 10:11 AM
#2
Senior Member
Join Date: Aug 2010
Location: Maumelle, AR
Posts: 613
Total Cats: 3
They're pretty light, less than 15 lbs, maybe even 10 (edit, quick search shows 11lbs)... most of the weight is at the ends, u joints and slip yoke. If it isn't aluminum already I can't imagine you'd save more than a lb or 2 going to aluminum.
Reply
0
0
03-04-2011, 07:28 PM
#4
Reply
0
0
03-04-2011, 11:06 PM
#10
But I was curious about driveshafts.
Reply
0
0
03-04-2011, 11:17 PM
#11
Right, sure. But the whole idea is to reduce rotational mass/moment of inertia. I'm just saying, if you're willing to go as far as lightening the driveshaft, you're doing yourself a disservice if you aren't already using the lightest flywheel/clutch and wheels that you can.
Reply
0
0
03-05-2011, 01:45 AM
#14
Since the difference would be minimal, I'm obviously not going to do it.
Reply
0
0
03-05-2011, 01:46 AM
#15
Right, sure. But the whole idea is to reduce rotational mass/moment of inertia. I'm just saying, if you're willing to go as far as lightening the driveshaft, you're doing yourself a disservice if you aren't already using the lightest flywheel/clutch and wheels that you can.
Reply
0
0
03-06-2011, 08:12 PM
#16
I've bought two miata's cheap (one for 1700, the other for 1750) with mint hardtops (and one in pretty decent condition) becaue the front u-joint broke on the driveshaft.
The driveshafts didn't fail because of high torque, they were both bone stock 1.6s. They failed because the bearings in the U-Joint degraded over 20 years of use. The first one lost the U-Joint, but the driveshaft didnt completely come apart, though it completely DEMOLISHED the rear section of the transmission case. The second driveshaft broke cleanly off at the u-joint and fell between the PPF and Exhaust without additional catastrophic failure. The front yoke remained in the tail of the transmission for a short period of time. When I went and looked at the car, the guy said it was driving and just quit a block from his house - engine ran fine, transmission shifted fine, but the car wouldn't move. I suggested that it could have been the driveshaft u-joint, then got on my hands and knees and looked under the car to see the front yoke of the driveshaft laying on the ground where it had fallen after surely spinning vainfully long enough to vibrate itself out of the transmission. I replaced the driveshaft in my built car after a cross country trip long before owning either of those two cars because the front u-joint
was making death threats to my car.
BUT....None of those failures were actually power related.
The driveshafts didn't fail because of high torque, they were both bone stock 1.6s. They failed because the bearings in the U-Joint degraded over 20 years of use. The first one lost the U-Joint, but the driveshaft didnt completely come apart, though it completely DEMOLISHED the rear section of the transmission case. The second driveshaft broke cleanly off at the u-joint and fell between the PPF and Exhaust without additional catastrophic failure. The front yoke remained in the tail of the transmission for a short period of time. When I went and looked at the car, the guy said it was driving and just quit a block from his house - engine ran fine, transmission shifted fine, but the car wouldn't move. I suggested that it could have been the driveshaft u-joint, then got on my hands and knees and looked under the car to see the front yoke of the driveshaft laying on the ground where it had fallen after surely spinning vainfully long enough to vibrate itself out of the transmission. I replaced the driveshaft in my built car after a cross country trip long before owning either of those two cars because the front u-joint
was making death threats to my car.
BUT....None of those failures were actually power related.
Reply
0
0
03-06-2011, 09:46 PM
#18
Newb
Join Date: Nov 2010
Posts: 9
Total Cats: 0
I try to change the U joints on my other vehicles every 50k, and even at that point they're starting to get worn enough to get stiff. A driveshaft shop once quoted me 900$ to make a CF one and I almost considered it just so I could replace joints. If I could find an aluminum one with replaceable joints for under 300$ I'd buy it, I'm planning on going back there some time to see if they'd seriously make me an aluminum for the Miata for a reasonable price. (They normally are making custom driveshafts for big trucks or trains or whatever people use massive driveshafts for, so I don't even know if their carbon fiber offer was serious)
Reply
0
0
