I feel like I'm taking crazy pills. (driveshaft problems)

[mike22b]

I took advantage of Shaftmasters ebay prices and got an alum one to replace my, for a long time out of whack, driveshaft.

My car has a J30 diff, i believe, and is of course manual, so ordering was easy. I got it in the mail the other day, and with much excitement I pulled the old one out today and noticed this.



They're not at all the same length.



Now, did I F up? The car has never had ABS, but having a j30 diff the driveshaft has to be abs length, right? And you can tell if you have an ABS VLSD if it's got that sensor, right?

my car:


So why is my replacement so short?

Then to make sure absolutely sure that shaftmasters messed up and not me I measured the old driveshaft and compared it to these specs

1st section (no difference for ABS/non-ABS):
M/T: 395.0mm (15.55")
A/T: 432.0mm (17.01")

2nd section (no difference for MT/AT)
non-ABS: 605.0mm (23.82")
ABS: 590.0mm (23.23")

and found out that it matches the length of a NON-ABS.

W
T
F

[Epstein]

You've got the right shaft.

Here's the deal. You've got an ABS diff. Your non-abs OEM shaft fits that setup, it's just tighter than Nissan designed. So the shaftmasters part should be 3/8" shorter. On top of that, the OEM shaft isn't straight. The 2 halves sit at an angle. A 1-piece would be the hypotenuse of that and therefore shorter. That accounts for the rest of it.

My shaftmasters part has 3/4" of exposed snout when installed. I suggest you just install yours and see how it fits. I'm betting it's fine.

[mike22b]

You're a real sweetheart Epstein, thanks for the speedy reply.

I didn't realize you could use a non-ABS shaft in an LSD, that might actually explain some of my vibration issues.

Anyways, here is how it looks installed. Still pretty short I'd say... but...



Looks ok?

[mike22b]

I measured the exposed bit and it's about 3/4"

I guess it's fine then, but the OCD mechanic in me doesn't like to see so much unused spline.

[Epstein]

That's maybe a hair farther out than mine. I just had mine on the lift this afternoon and noted that it was easily a thumb width.

[98koukile]

I'm about to do this switch but I need to make a dust shield

[mike22b]

I drove around and the car was 100% vibration free, it was really great. Before, at around 25mph, the shifter would bounce back and forth violently and the whole car would shake.

I can't comment on throttle response or any of that na na, but it certainly looks cleaner and brings the overall weight down.

You reckon this calls for a dust shield?

[Def]

There's a factory dust shield that goes there. Look it up on www.courtesyparts.com

It should cover almost all the splined part up.


What was the weight difference between the aluminum and stock driveshaft? I'm thinking about giving this a go to drop some weight.

[98koukile]

8 or 9 lbs? I'm not even sure. I know its almost half the weight

[mike22b]

I didn't weigh anything, but you sure as heck can feel the difference.

[a_ahmed]

well its 11lbs the alum 1piece, so the stock thing is like what 20lbs? So yeah 9lbs sounds about right. Oh yeah don't lick your fingers when you touch this driveshaft :P Aluminum is poisonous mwahaha. It's completely raw aluminum, no coating or plating or anything :P Got my hands all grey from touching it..

[Caithness]

I drove around and the car was 100% vibration free, it was really great. Before, at around 25mph, the shifter would bounce back and forth violently and the whole car would shake.

I can't comment on throttle response or any of that na na, but it certainly looks cleaner and brings the overall weight down.

You reckon this calls for a dust shield?

If you still have your stock driveshaft hanging around (and you don't mind spending a few minutes to satisfy my curiosity) check the nuts and bolts holding the rubber coupler at the front of the driveshaft together. One of mine was loose and caused a vibe like you experienced at ~25mph. It actually loosened all the way and shot out from the shaft at high speed while I was driving- quite a loud and unnerving noise. I threw a new bolt in there which brought the vibes way down but they didn't go completely away. Solution: new shaftmasters aluminum one piece, going in with my new engine and tranny.

DSS lists their aluminum shaft as 11lbs and I always hear 20lbs thrown about for the stock shaft. I'm going to try to remember to throw my shaftmasters shaft and the stocker on my parts scale just to see what kind of dead weight I'm getting rid of. MOI decrease isn't anything special for the price- I'm in it to ditch that horrible rubber joint and carrier bearing more than for anything else.

[Epstein]

I've weighed the stocker in at 22 lbs before. Both my Enjuku and Shaftmasters are 11-ish pounds. I also had a local 1-piece steel shaft built that came in at 15 lbs. I wouldn't expect much variation between manufacturers with the same materials. They all use Spicer ends and joints. I've also seen low-speed shifter hopping action with a dead stock shaft. Also groaning rear u-joints on 2 different ones.

And you're not going to get an improvement in throttle response with a driveshaft because the period in time when you'd see that, the change in DS speed is negligible. Or you're in neutral / have the clutch in, in which case the DS isn't even connected to the engine.

[98koukile]

I thought the improved throttle response theoretically came from no carrier bearing... the driveshaft has no up and down movement to lose energy so it reverts it straight into movement. Other than that I see no other argument really being feasible.

[Epstein]

No carrier bearing and no up/down movement would go towards improving drivetrain efficiency. That's not throttle response.