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Rooy · Joined: 16 Jul 2005 Posts: 41 Location: Neenah, WI

I've had this horrible vibration whenever the driveshaft is spinning that comes in at 3200 rpm and smooths out by 4000. The vibration appeared after a spirited driving session, as I came out of a tight ess, and mashed the throttle in 2nd, taking it to redline up a moderate incline. The car is a '78; the torque tube and 5 speed trans are out of an '81. As soon as I got the trans out I spun the driveshaft and it was obvious that it was bent. The bend is about 14" from the trans end of the shaft. The first bearing sits about 4" into the tube. I measured the distance the shaft is supposed to protrude from the the trans bellhousing, and it came up a little short, about 10mm when the spec is 19mm. I can't be sure it was like this, however, because it took a great deal of force to separate the tube from the clutch bellhousing, and it's possible that the tube moved over the shaft a little bit when pulling it back.

Also, I'm pretty sure I didn't get the trans hung up on the shaft when taking it out, thus causing the bend, but I did have some problems maneuvering down, so it leaves this as a slight possibility in the back of my mind. But even if I did, I don't think it makes sense in relation to where the bend is. It is bent after the first bearing, where I would think it would bend just before it if something was levering on the end of the shaft. And it only makes sense that this may be the source of the terrible vibration.

Anyways, I removed the bearings, which was a tiring job, jamming my pvc pipe in and out with as much force as I could muster. Lots of penetrating oil really helps to get these moving. I also discovered the mysterious vibration damper, simply a heavy iron cylinder with two thick rubber mounts, that no one seemed to know anything about during my previous quests here to track down this vibration. Definitely not the problem. The bearings seemed fine, also. They felt just a bit gritty, but otherwise they were all tight and spun great.

Here's a couple pics of the bent shaft:
http://img153.imageshack.us/img153/534/dscf16353ti.jpg
http://img73.imageshack.us/img73/7984/dscf16372jo.jpg

The bearings and the vibration damper:

Empty tube:

Well, now my focus is to find another torque tube locally. I am also going to look into what it would cost just to have a new driveshaft made up, as I can get the steel cheaply. It would just have to be turned down to the proper size and then splined. Seems do-able to me.

Any thoughts on all this?
_________________
Andrew
Neenah, WI
'78 924 with dual Dellortos

Paul · Posted: Sun Jun 04, 2006 11:17 am Post subject:

I'm thinking that shaft can be straightened if you can find a long enough lathe!
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Neil924 · Joined: 18 Mar 2003 Posts: 4225 Location: Canada

Joes924Racer · Posted: Sun Jun 04, 2006 12:06 pm Post subject:

Hmmm I had the same type of vibe at the same rpm
though I tracked it down to being a busted coupler.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Paul · Posted: Sun Jun 04, 2006 12:43 pm Post subject:

http://www.hinesindustries.com/aftermarket/press.html

_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

PORSCHEV · Posted: Sun Jun 04, 2006 10:01 pm Post subject:

I think it would be best to find another TT or driveshaft. Had to believe it bent like that!

It would be very hard to straigten IMO....the lathe can't be used to actually straigten it but only check it really. It would need to put into a press and I wouldn't reccomend using any heat.

As for having one made....it costs ALOT to have splines cut like that ,not to mention your not dealing with run of the mill.....mild steel here.
_________________
1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

Paul · Posted: Sun Jun 04, 2006 10:53 pm Post subject:

Unless you know an old timer that's good at doing this (for a few bucks), a used TT is a better idea.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Vince Ponz · Joined: 02 Nov 2002 Posts: 3581 Location: Florida

I have a torque tube but I think it is too big to ship. Your call. $50 plus shipping. ????
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

Rooy · Joined: 16 Jul 2005 Posts: 41 Location: Neenah, WI

Hi Vince, it is shippable. UPS will ship it, but I think it falls into their "large package surcharge" category (+$40), but just barely, and maybe not depending on how they measure it. Total cost from NY --> WI appears to be ~$75, if my measurements are correct.

And Greyhound (depot to depot) is a great option for large items. They want $74 to ship it.

I'm going to check with a few junkyards around here first and see if anything's available, but I will definitely be keeping you in mind if nothing turns up. Thanks!
_________________
Andrew
Neenah, WI
'78 924 with dual Dellortos

Paul · Posted: Mon Jun 05, 2006 1:33 am Post subject:

I have one for a 81-82 931 or 944, but I think you need the smaller one....
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Rooy · Joined: 16 Jul 2005 Posts: 41 Location: Neenah, WI

Vince Ponz · Joined: 02 Nov 2002 Posts: 3581 Location: Florida

I think you might be in luck at the junk yard. I could ship mine if you like.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

Porscheaddiction · Posted: Sat Jul 29, 2006 3:04 am Post subject:

Rooy · Joined: 16 Jul 2005 Posts: 41 Location: Neenah, WI

It's the coupler between the driveshaft and the transmission. You can see it through the access hole in the trans bellhousing. You should be able to tell if it's broken just by looking at it (look at the welds). Turn the driveshaft some to get a good look at all sides of it. This vibration you have...tell us more. Try this: stopped, in neutral, with clutch depressed, rev the motor slowly through the range where the vibration is apparent, and see if it's there. Then try again with the clutch out (not depressed). With the clutch in, the driveshaft is not spinning, and vise versa. That may help narrow it down some.
_________________
Andrew
Neenah, WI
'78 924 with dual Dellortos

Porscheaddiction · Posted: Sun Jul 30, 2006 3:36 am Post subject:

ok heres what happens.
start up the car and while its warming up to operating temp it will sometimes vibrate if the revs drop down abit doesnt matter if the clutch is depressed or not. (sign of worn out mounts? ) . Now after the car is warmed up the vibration is not present in neutral at all clutch in or out. But when driven when approximately 3200rpm is reached its there and quite noticable as u climb up in revs it disappears and it seems to do that in all gears. Now I do know one side of my CV is finished and both will be replaced soon but I dont see that as a cause of vibration going in a straight line and feeling the vibration in the drive shaft tunnel just behind the gear shift . I havent looked at the coupler but from everyones experience does it sound like that could be it?
Thanks
Chris.
_________________
1981 924 NA (Restoring mode)
1984 928S (Enjoying the driving season)