What's Normal Noise From a 915/40?

[JTO]

Hi Folks,

I need some definitive information about the noises expected from a 915/40 in my 1975 911 S.

I have had the tranny rebuilt about 200 miles ago. I have a wine in both third (subtle) and in fifth (noticable) under acceleration and while cruising in fifth. When I let off the the throttle, wine goes away. Is this normal?

Also, there is what I want to call a "munch munch munch..." sound at very light throttle, eg, around town and then a gravely noise when compression braking from low speed. Is this the 915 rattle that caused Porsche to adopt the rubber centered clutch?

Some info would be very appreciated! Thanks,

Troy

[beepbeep]

whiiiiiiinnnnneee....crunch.....whiiiiiiiinneeeee. ...grooowl....groooowl....whiiiineee.....crunch... .munch, munch....whiiiiineee



P.S.
Light-throttle bucking @ low RPM is almost always worn CV's...

[JTO]

I've got new half shafts, wheel bearings, clutch, etc, etc.

Troy

[cstreit]

Hey beep beep, that's MY 915... weird

[Oldporsche]

I dunno,

The sound of the 915/40 in my '75 sounds like its grinding coffee.

Absolutely nasty!

I expect to take it apart one of these days, if it doesn't do anything bad in the meantime.

good luck,
David Duffield

[JTO]

What? Did everyone put an extra scoop of funny stuff in their coffee this morning?

Any "serious" responses out there? I guess I should know better than to ask a serious technical question on Friday!

Troy

[Early_S_Man]

Troy,

Do you know what kind (wt & brand) of gear oil is in your transaxle? Have you checked the oil level lately?

Low-rpm rattle is indeed what the rubber-centered disk was developed to remedy!

Have you discussed the other noises with the shop that did the rebuild? They do not sound normal to me!

If the shop suggests 'waiting out' the other noises for a thousand miles or so ... I suggest changing your gear oil immediately, and putting in Valvoline 80W-140 Gear oil now, and change to Swepco 212 at 1000 miles. The correct change qty is 3.2 qts. Add some Kendall (or other brand) limited-slip additive to the Valvoline gear oil in your 915 during the break-in period.

[JTO]

Thanks Early_S_Man,

I have indeed spoken to the shop who rebuilt the tranny. I have sent it back once already, and the noise is much improved (it used to whine all the time).

I am running Valvoline 80W-90 right now. Do you suggest I drain this and add the viscosity modifier and the heavier fluid?

Any other hints? What could cause this whine under power and not occur coasting?

Thanks again,
Troy

[Early_S_Man]

Troy,

The limited-slip additive is a friction-modifier like Molybdenum Di-Sulfide, and other compounds.

Yes, I recommend changing your gear oil now ... to get any wear particles from the first 200 miles of usage out of the transaxle.

Whine under power, quiet after backing off sounds like bearing noise to me. Hard to say which bearing for sure. Were all of the bearings replaced during the rebuild?

[JTO]

Early_S_Man,

I was told that all of the bearing were replaced. I will change the fluid out this weekend.

Thanks,

Troy

[beepbeep]

When you lift the car to change fluid, try to twist halfshafts back and forward and see if there is any play in the CV's. There should be some longitudinal but no axial play.

[ohecht]

I have been running SWEPCO since owning the car, and it has recently (or always) made a weird, almost "hissing" noise if is bogged down (i.e. rolling from lights that turn green in second, or after early shifts to third)

The odd part is that the noise is clearly coming from the shifter area, and I know the transmission and clutch are behind me mostly.

Olivier

[JTO]

Olivier,

I hear the sound from the shifter are too. I assume that the tunnel or shift linkage act as a conduit for the sound to enter the cabin.

Troy