sick 915/differential - diagnosis in progress

MuffinMan · 10-06-2005, 11:02 AM

During the winter of 2004, I had some extensive modifications performed on my 911, including a 3.6 conversion and a full 915 tranny rebuild. Unfortunately, my transmission/differential was not happy at Porscherama, and now the fun begins.

I took it to a friend who is just setting up shop and has a shiny new lift waiting for patients. Upon initial inspection, it looks like the differential bearing is shot, and hopefully it didn't take the ring & pinion with it. While I'm no expert, this doesn't look good. I'll post the progress, but I'm not sure if this pumpkin will make it out for halloween

Waiting to go under the wrench

john walker's workshop · 11:59 AM

from the video, it looks more like the carrier is broken.

KobaltBlau · 10-06-2005, 12:43 PM

Good Luck, Rob. No more dropping the clutch at 5600rpm with that varioram!

MuffinMan · 10-06-2005, 01:22 PM

The work continues...

MuffinMan · 10-09-2005, 04:07 PM

Houston, we have a problem.

Well, disassembly of the transmission revealed a failed bearing. I'm not sure what the bearing is officially called (perhaps carrier bearing?), but it's one of the bearings on the differential "shaft", where the CV joint connects. A few of the rollers were missing when it was initially removed, and a bunch more fell out during the inspection.

The big problem is the ring and pinion are absolutely friggin' destroyed. The pictures are not for the weak of heart! It looks like a new pinion shaft is ~$4700, so I think I'll be taking a different repair route. What's the common "fix" for a bad ring & pinion? New parts? Purchase a used transmission and extract the ring & pinion? Purchase just those pieces used?

Nevertheless, here they are

NoLift911 · 10-09-2005, 04:31 PM

That is some serious carnage - what went wrong? This was rebuilt in 2004? Something overlooked...crappy job? Who did the work?

-Jeff

Nickatnyt · 10-09-2005, 04:33 PM

day-am! Makes me want to save up as much as possible for this sort of tragedy.

Dan J · 10-09-2005, 05:33 PM

Rob,
Time to call Gary Fairbanks
Dan J

john walker's workshop · 10-09-2005, 06:02 PM

i have R+Ps used for $450 w/shims.

MuffinMan · 10-10-2005, 05:04 AM

Quote:

Originally posted by john walker's workshop
i have R+Ps used for $450 w/shims.

I'm going to see if the shop that did the rebuild will provide any sort of "warranty", otherwise I will be giving you a call on those parts. I literally laughed out loud when I saw the new parts cost.

Ah, the joys of Porsche ownership

Bill Verburg · Bill Verburg's Garage

Rob, Sorry to hear this

The first thing I would want to know is why it failed. Was it the side plates flexing, the pinion bearing flexing? defective bearings? or what?

NoLift911 · 10-10-2005, 06:36 AM

Ditto what Bill said -

That carnage is not from normal wear and tear even for a 3.6

Something was defective or installed incorrectly. I would show up on the rebuilders door step with those parts in hand along with my case and ask when it will be ready for pick up...

-Jeff

MuffinMan · 10-10-2005, 10:13 AM

Quote:

Originally posted by nolift911
Ditto what Bill said -

That carnage is not from normal wear and tear even for a 3.6

Something was defective or installed incorrectly. I would show up on the rebuilders door step with those parts in hand along with my case and ask when it will be ready for pick up...

-Jeff

lol...I've definitely considered it. I'll keep you posted on the course of action! I definitely want to figure out what caused the tragedy...

Geary · 10-10-2005, 10:55 AM

Sometimes the magnets come off the speedo ring causing damage. How the diff bearing got like that is questionable, though. The race was probably bent previously during bearing removal.

MuffinMan · 10-10-2005, 12:42 PM

I spoke to the shop that did the rebuild, and they are fairly positive that the side plate was deforming/twisting, allowing the bearing to move & eventually fail. They said the bearing on that side is the "power side", and is typically the first one to fail. I do have a later side plate from an aluminum 915, but I do not have a heavy duty billet plate. The shop owner also said one of the HD cover manufacturers was discussing a plan to make a larger opening to accommodate a turbo bearing to further reduce the chances of any problems in the future.

That's the update...it looks like I'll be contacting John for that used R&P, and purchasing some other pieces from our good friends at Pelican.

Bill Verburg · Bill Verburg's Garage

Quote:

The shop owner also said one of the HD cover manufacturers was discussing a plan to make a larger opening to accommodate a turbo bearing to further reduce the chances of any problems in the future.

That's the Wevo side plate. It does use the 930 bearing.

Bill Verburg · Bill Verburg's Garage

Quote:

spoke to the shop that did the rebuild, and they are fairly positive that the side plate was deforming/twisting, allowing the bearing to move & eventually fail

That was my first thought, I have seen signs of distortion there from the bigger displacement engines mated w/ 915s. I think that hard acceeration in lower gears(as in A/X) exacerbates the problem.

MuffinMan · 10-10-2005, 03:45 PM

Interestingly enough in an email exchange with Hayden, from WEVO, he suggested that the failure was from a damaged bearing prior to installation, as opposed to from side plate flex.

john walker's workshop · 10-10-2005, 04:46 PM

yeah, you just don't see those bearings fail like that.

Bill Verburg · Bill Verburg's Garage

I've noticed several 915s behind 93/964 engines weeping fluid out of the side seal. That tells me something is going on there.