Help -- Knock, Knock, Knock ....
 

Hi all-
I have an 82 911sc with 150K+ miles ... I just drive it during the summers (I'm in New England). I had it out a couple times already (driving around town) and it seemed be running fine.

But yesterday after it was parked outside all day (fyi- 80 degrees), I cranked her up and it looked like it blew a tad of smoke. I thought it ran fine but when I got close to home (10 miles), I noticed a "knock, knock, knock" from the rear end (I think Left side).

Details: (1) it went away when I took it out of gear and started coasting; (2) it did not re-appear when I rev-ed the engine while in neutral; (3) it came back when I dropped it in second gear (low rpms); and (4) it seemed to get better when the speed increased.

The oil pressure seems fine (3-4 while driving) and the oil level is high (I may have put a little too much up a couple weeks ago).

Rod? Broken Stud? Too much oil? Tranny?
Help (I'm a novice when it come to these things).

____^^^____^^^^______911scVT

Check your CV joints, maybe the flange bolts loosened up? A little puff on start up is not uncommon. Mine does it once and a while.

What John said. Sounds like a cv flange coming loose. Do not drive the car until you check all the bolts!

Hmmmm-- all bolts seemed tight .... Any other thoughts?
Thanks.

When you stand behind it with the engine lid up at idle, can you hear it? I know you said it went away when coasting but road noise may muffle it. If you hear it at idle standing behind it, mine was is the same sound which is the intermediate shaft knock. There is a thread I started months ago about this and the board said turn up the idle, it is still there but not as loud. I did this and have put 1000+ miles on it and it is a happy SC. I am sure when I go to sell it the sound will scare potential buyers away but it runs great and has excellent oil pressure so I have been enjoying the ride.

Diagnosis and Cost estimate ....
 

The folks who responded were on the right track ...

I was told that I need a new rear axle shaft.

I really like my mechanic, but I'm curious how much people think it would be for parts and labor?

I realize that it will vary, but I'm just trying to get a sense ...

Its a pretty straght forward deal to replace an axle. I think a whole assembly is expensive but you really just need to replace the CV which is still a couple hundred I think but not bad. Tons of threads on replacing/rebuilding the CV. Any interest in trying it your self? I think its covered in Waynes book?

Thanks for the reply. Evidently, it's the actual shaft -- not the CV, that just wore out. I think it is the original axle (150K+).

easy replace yourself. be sure to tighten the bolts properly and check them after a few miles and again after 1000 miles. I believe our host sells them.

If you are planning any serious engine upgrades (ie Turbo or supercharging) any time in the future I think 964 axles might also fit in and are a lot beefier. Seek confirmation those (911 332 024 14) fit your 915 box though. I know it fits my G50 but I dont have a 915 here to compare the bolt pattern and length.

1 axle assembly, see pelican parts catalog for price. labor about 1/2 hour, $50.

Mr. John Walker,
I think that you are waaaaayyyyy too on-the-level to be a Porsche mechanic! labor - $50 ???

I was thinking the same thing. If I lived near his shop I might be tempted to let him do some of my work at that rate.

The rate, of course, is a perfectly reasonable $100/hour for somebody of Walker's rep. What makes it unusual is that he'd charge for just the actual half-hour. I think most shops have minimums of an hour and then some. But you're right, the guy is a huge resource, whether you're near enough to use his work or simply on this forum to listen to him. We're fortunate to have his input.

Absolutely. The 100/hour rate is perfectly normal. But like you said, only charging 1/2hr labor is the difference between John and the rest. And yes, he is a huge resource here. I read every word he writes and I even print some of it for future reference.