This afternoon, I swapped out my driveshaft for another because part of my front U-joint was frozen, making the car vibrate like mad about 20mph.

While I had the old one out, I noticed the two looked different. The one on top, the original driveshaft from my early 86 Sport, is fat and has a dustcover for the input side. The lower is the one I scavanged today from a guy in my neighborhood, it came from an S4 GXL (year unknown.) It looks pathetically thinner, but it fits and works just fine.

Anyone know the story on the thin one?

 

Now that is werid, never seen a S4 tailshaft that is that skinny?! Only ever have seen them the size of the large one in the pic.

Obviously has a new yoke on the front(no dust cover). Maybe it was bodged up from some other car with a new front yoke put on? (maybe early first gen '7?)

 

My friend's Sport had the same thick driveshaft. I'm not really up on the pre-88 parts because I bought my first RX-7 in 1988, and the 88 manual is the only reference I have for the S4 RX-7, but the thin driveshaft is the standard NA driveshaft on the 88 and later models. I'm not sure if the thick driveshaft is unique to the Sport, or if it was just the standard driveshaft on the earlier models. Maybe some of the 86 RX-7 owners can help?

 

Well I have an "85" S4, my mate has a 88 S4 both N/A, they have the same driveshaft... (the thick style one).

Also another mate with a S4 turbo has the same thick tailshaft(different yokes/length obviously).

Every single FC i've ever seen in Aus has had the thick tailshaft. Admitadly I havn't had a look at too many S5's, but for S4's at least it would seem its the only tailshaft there was?

Maybe this was just some US thing you guys lucked out on or something.

 

bottom is s5 shaft, top is s4 shaft. Just different series.
for example, my '90 n/a is identical to the bottom shaft.
WhiteFC's shafts for his '85 are identical to the top.
problem solved

 

Hmmm strange, wonder why they did that to the S5's? Was it for weight purposes?
Was it just on the S5 N/A's? or did the S5 turbo have the same small one aswell?

 

No, my 88 NA had the smaller diameter driveshaft. Also, the 88 factory service manual lists only the smaller diameter driveshaft for the NA MT cars, but the NA AT and TII cars had the larger diameter driveshaft.

 

I can't really relate the thickness of my 90 GXL... it could be either, but I can definately state that there is no dust boot over the tranny output shaft.

 

No dust cover generally means its an aftermarket yoke.

I'm near on 100% certain my mates 88 has the thicker t/shaft...

So does anyone know why the moved to the smaller tailshaft? is it much lighter (if at all..)?

 

i have an S5 turbo.. thicker one with the dustcover here

 

The drive shaft I bought from Mazdatrix did not have a dust cover. The balance weights looked like simple washers tack welded to the side. Not saying it is good or bad but that's how it looks.

I think all 3 drive shafts I have (1 OEM '86, 1 OEM '91 and the one from mazdatrix) are all the smaller dia. I'd have to double check to be sure though.

All for N/A 5-speeds.

 

My origonal 91 NA shaft was smaller.
It's replacement was bigger.
Can you spot the bad U-joint?

 

I remember once reading something about Mazda using a dual concentric shaft for their driveshafts. If that is true, than that may explain why some Mazda driveshafts are a smaller diameter than others. I have a 90 GXL, and it has the smaller diameter driveshaft.

Also, the NA S5 trannys have an internal balance weight on the output shaft whereas the NA S4 trannys have no internal balance weight. I've always thought that the thing you folks are calling a "dust cover" was actually a weight that was added to the NA S4 driveshafts since the NA S4 tranny does not have an internal balance weight.

Hot_Dog
90 RX7 GXL
02 Acura RSX-S