Propeller Shaft Failure?
 

My race car has started making a wheel-speed dependent noise recently. It's a scratching noise that's only present at no or low load on the drivetrain like a 40mph cruise or when coasting with the clutch in. The noise goes away when I turn either direction. The noise appears to be coming from the center of the car. I'm familiar with wheel bearing failure noises and this is similar but it did not get worse after a full day on the track.

My propeller shaft (most car manufactures call it the "drive shaft") has some runout and slop. If I hold the transmission output shaft and twist the propeller shaft I can feel a little play and the same happens if I hold the differential input. If I push and pull the shaft vertically I can feel a little slop too. I crawled under my wife's low mileage 2006 S2000 and the prop shaft is tight as a drum in all these tests. When I turn the drivetrain by hand under the car there's no obvious extra noise compared to my wife's car.

So I know my prop shaft is out of spec but would it make the kind of noise described above? After research it seems they normally make a clunk or vibrate at speed. My race car vibrates a lot from the aftermarket stiff motor, trans and diff mounts so I haven't noticed any extra vibration.

Is it possible to rebuild the prop shaft or is replacement the only option?

Thanks in advance for any help,

Rob Robinette

Is the play in the CV's or in the length compensation part, where it slides on splines?
(or both?)

You can put fresh grease in the CV's but it will not heal a worn CV.
You can have a look at the CV's balls.... ;)
I don't know if you can get replacement CV's.
IMO when that splined sliding part is done its done, its welded to the propshaft.

Last time I had the propshaft out I tried to "pull" it apart but it would not.
It felt the 2 parts have some flexible bond and it would snap back, like the caliper sliding pins, but that's vacuum by grease.

:hello:

The drive shafts and CV's feel pretty normal.

I forgot to mention the transmission is original with 57k total miles but lots of hard track miles. The differential is a low mileage AP2 Puddymod rebuild.

The prop shaft also has CV's, at both ends, like the axles (drive shafts)
They look simular to the (compact) outboard CV's on the axles - and not like the inboard cup & spider CV's close the diff.

:hello:

I think Eric (username ummpwr on here) fell into a similar prop shaft issue at CMP one time... I remember him telling me about it, but I cant remember if it was the prop shaft or axle that he ended up swapping out to resolve it... I'll point him to this thread to see if he can offer anything.

Sorry Spitfire, I thought you were talking about the driveshaft CVs. I'm not sure where the slop is coming from, I'll have to check it again.

On a related note, the Driveshaft Shop has a lightweight aluminum prop shaft with real universal joints that should be replaceable. Anyone have any experience with it? I did a search and found nothing about it. It can be seen here: Driveshaft Shop Prop Could be an error because driveshaftshop.com shows it as an AP2 part. Anyone have experience with their steel driveshaft? It uses u-joints too.

Ive had a very similar noise, A roaring rotational sound from the center rear of the car at 50mph range, mine would get louder with speed. I also have stiff engine tranny and diff mounts so vibration is normal for me. I had a driveshaft shop alum DS that was out of bal, it made a vroom , silent, vroom , silent at dependant on wheel speed so I took that off and put my stock one on thinking the driveshaft was out of bal. It helped alot with the vibration feel and some with the noise but I still had a quieter noise.

One day on RRR track the noise and vibration go much worse and I found that the bolts holding my axel LR to diff had snapped on one side (found out when I could not move the car in pit lane!!!) I found my broken bolts like a trail leading back to my camping spot! I replaced them but still had a very loud vibration. I found that my RR wheel bearing had play and replaced it. The car was now driving smooth. But last week before I went to CMP I started to hear the roar from the rear again so I replaced my LR wheel bearing thinking it has never been replaced in 147k. That did not help much. but everything seemed ok after a weekend at CMP.

Then This Sat I went to VIR and after sat my noise from the rear has seemed to get louder and grows with speed. The car also feels like its hopping at lower speeds below 40mph.

So a wheel bearing has cured my problem once but now I have the smiliar noise and two new wheel bearings! could the stock driveshaft be out of bal?

Eric

Eric, thanks for the input. I checked all my driveshaft bolts when I was under the car and they're good and all of my wheel bearings have been replaced at least once but I haven't ruled out a bad rear wheel bearing.

I'm going to replace the prop shaft anyway, I just have to decide to use OEM new, used or Driveshaft Shop prop shaft.

Sure, I believe the stock one comes bal. but it would be good to know if yours is out of bal? also I had a older driveshaft shop driveshaft that was very difficult to install, I think they have updated the adapter plates and how its mounted. Let me know what you have decided.

Eric

Eric, it seems the OEM propeller shaft is balanced in place because the Workshop Manual has you mark the shaft's orientation before removal so you can reinstall it matched up correctly to the transmission output shaft and diff input. I couldn't do that when I installed a Puddymod diff a couple of years ago so maybe it was slightly out of balance.

After doing some research I went ahead and ordered the Driveshaft Shop's light weight aluminum propeller shaft for the AP1 which is part # H0SH1 (H0HS2 for AP2). I ordered from THMotorsports.com. The owner is an S2000 guy and he's running this propeller shaft on his car. The price was $767 with free shipping. A new OEM unit online was about $900 + shipping. The Driveshaft Shop also sells steel propeller shafts for about $90 less than the aluminum. There were lots of used shafts on ebay but I'm afraid that most of the AP1 shafts would be too high mileage.

I like that all the Driveshaft Shops shafts come with universal joints that are replaceable. A downside is they build these to order so it will take some time before delivery.

I don't know if this will solve the noise issue that started the search that led to discovering the bad propeller shaft CV joints but I've got my fingers crossed.

I'll update this thread with the installation comments and whether the noise goes away.