My problem with the dif was just some noise coming from under the seat area right when I was letting of the gas and the driveline had some slack/ drag on the trans. When I put the car on the lift and went over it with a stetoscope I tracked the noise to the front differential. I searched all over the internet for info pertaining to taking the diff apart and rebuilding it but the only thig I came up with was this :
http://blog.titanmotorsports.com/?p=293

so I figured out I'll jump into it and tear it apart.

After seeing these pics and checking out the diff in person, I'm not surprised that it went kaboom. There is no way that this thing could sustain more than 50% of the output that the engine produces.


I took it apart. Breaking it down into the tailshaft, clutch, front case and ring gear assembly literally took 10 minutes. This thing is really a no brainer and you can replace 50% of the bearings without any advanced tools.

As far as the viscous clutch, it's the only thing I wasn't able to take apart (actually my buddy stopped me) as it is welded shut pesky italians (said made in italy) don't want you to know what's inside. If anyone has a broken one they'd like to donate to science, send it my way and I'll take it apart and post pictures.

As far as testing the functionality of the clutch, there is a detailed procedure in the shop manual that tells you how to go about it without breaking it and it had to be assembled on the car to do so.

I'm gonna post a bunch of pictures from the whole process and I'll be editing this thread as I progress. The repair manual doesn't give you part numbers for anything other than the 2 shaft seals, a tailhousing o-ring and the megabucks viscous clutch and there is no diagrams available that I was able to find that show you a breakdown of this thing so I took plenty of pictures. My goal is to create a list of most parts inside however " if it ain't broken don't fix it" so I'm not gonna take apart what I presume is OK so no part numbers for parts I cannot see that don't need to be dissassembled in my case.

Here is the pics:


The front diff taken out of the car.

Below is what imidiately grabbed my attention. When the dif was on the car I noticed that there was a little bit of seepage. Nothing major thou as I drained the oil and it measured up to be exactly 1.5L. What I later found out is that this is the bearing that was making the noise. Good thing I caught it in time or it could've looked like the dif that exploded on the Titan guys.

This is the clutch in the main assembly. To take it apart there is a clip inside where the splines are that needs to be removed in order to slide it out. Needle nose pliers worked like a charm as it's a tight fit to slide something in there.

This is what you see looking at the tailshaft assembly.

Nice needle pilot bearing inside the tailshaft.

This is the clip that retains the viscous clutch.



Once you remove the clutch.

As you can see below there is a big nut holding down the bearing for the pinion gear that would require a pretty deep socket to be disassembled. Luckily there is no need to touch it.

Cover for the Ring Gear assembly what surprised me is the lack of shims. The "sie germans" are pushing perfections at us again.

Ring Gear along with planetary gears pop right out when lightly pried from both sides.

Pinoin Gear

This is the bearing that needs to be replaced. When spun by hand I could totally feel the vibrations.



Another look at the culprit

Yours truly

Below is the bearing that I need to replace as it is clearly shot. when you spin it by hand you can feel that it is not smooth.

The clutch is that big thing on the left, on the right are the axle shaft thingies and almost all tools required to take this apart.


I'll post more and edit this as I dig deeper.

 

Awesome write up!

man, I can't wait for my kids to grow up a bit more so that I can start getting my hands dirty again... wait one should never wish for life's fast forward button.

While on the topic, I have inquired extensively on the torque transfer abilities of the 996 TT. I did my own donut test once on the skidpad. I have looked at a lot of you tube videos of people playing around and doing donuts etc, even in snow the cars don't seem to spin the front tires. What gives?

http://www.youtube.com/watch?v=MGaSNLh9B_Y

this guy seems to get a good amount a wheel spin in a 997 and impresses the pants off the chick:

http://www.youtube.com/watch?v=urnGh9Gek2k

 

excellent, now a very important question for you.....do you think you can fit an LSD in there?

I just purchased a spare front diff and was planning on using it to install an lsd in the front to go with the one in the back.

 

Dennis,

yes, we plan to add a front and rear LSD in a RUF 996 soon.

 

Todd
yup, I found an lsd that may work, but will wait till I have the front diff in hand.
D

 

If you ever take it apart you'll understand. The clutch itself is sort of like a torque converter that never fully locks. So it will not fully engage no matter what. Kindoff like if you're stuck in snow and your wheels are spinning and someone is pushing you out, the wheels are spinning but whoever is pushing does majority of the work to move the car. I'd really like to put the 997 diff side by side with the 996 so I could compare them....anyone wants to borrow me their 997tt diff so I can take it apart and take pics?

Anyway heres a pic of the 997 diff of the getrag website. it does look more beefy:

 

The part number of off the ring carrier is 964.332.212.2R.

Honestly, an LSD in the front of a 996tt would be useless as it's not like either wheel will ever break traction. I think it might be a better idea to hybrid a 996tt front diff and a 997tt diff as they seem to be closely related.

 

interesting. you don't think an lsd will help direct power based on what you see?

 

LSD mechanically directs the power to the other wheel on the axle when one wheel brakes traction. Have you ever broken traction with either one of the front wheels when accelerating or at least felt some torque steer? Unless the issue of the vicous clutch directing more power to the front wheels is resolved installing an LSD would probably create more drag than it would benefit.
Also, the ring gear diameter is barely 148mm (~5.8inches), the case appears to be only about 1/16th of an inch thick in spots and according to the Getrag website the 997tt diff is rated up to 400Nm max which equals to about 295 lb/ft of torque. A 996tt in stock trim has 415lb/ft which is a conservative rating, therefore I'm not surprised that the clutch is not made to turn the car into a FWD machine at a click of a button like an EVO which is actually designed as a FWD with an AWD system piggybacked onto it.

The only way I can think as to how the 997tt is able to direct more power up front is that an electromagnetic clutch can engage and disengage/modulate the axles at an instant and as soon as traction is regained up front the power shifts to the back. I'm sure it's more complicated than that thou with the computer comparing signals from the ABS sensors, the ECU looking at the engine load and output. But basically and electronic system can possibly distribute the load more efficiently and safely without the requirement of a safety margin that the mechanical setup has.

 

Fantastic work my friend, I recently dropped my tranny in my garage to do some clutch and gearbox work.

Superb job Excellent write-up with pics!!!!!!

What were the symptoms of the front diff going out?...was the noise a whine or vibration?

Cheers,

Ben

 

Very subtle whine, a little high pitched but you had to turn off the radio to hear it and it was only when letting off the gas. I'm a bit **** when it comes to stuff like that and when there is something out of ordinary going on with the car I usually spot it right away. Once I know it's there it really annoys me. At this point it wasn't really a problem but preventative maintenance is way better and cost efficient than when things lock up and take out other parts with it. I already priced out the bearing and it's $25 with change vs $3000 for the whole thing. I'm also gonna change the seals while I'm at it and the bearing on the other side, everything else looks nice and tight. There is shims under the bearings which are used to set up back lash so I'll chime in on that once I see if any additional adjustment is necessary.

 

So, I put everything together today and figured I'll post the rest of the pictures for those of you websurfing on a saturday night. I'll edit captions later and explain what I was doing. Here they are:


But first I promissed I'd get you a list of bearings and components:


Ring Carrier:
*** 6008.C3
*** 6208.C3


Pinion Gear:
*** 30206A V HD (2 pieces)


Pilot Bearing in the output shaft/tailshaft:


HK1212 R INA


Tailshaft (Clutch Side)
*** 16007.C3


I guess the only one I wasn't able to get to is at the end of the tailshaft. Other that that it's all there, all the bearings can probably be had for under $300.

 

look good man were those bearings sourced locally or ata porsche supply house?

care to share cost of all that?

 

I only replaced 2 bearings, the ones for the ring carrier. I got them from http://www.motionindustries.com, they were local to me and the cost for both was about $75 ($25 + $45 + tax). Only one was busted but I figured that the other side might be going too since the one was binding. The seals and the o ring I got from the porsche dealer. The other o-ring I reused and used some RTV on both to make sure there is no leaks.

 

nice, i always source bearings locally too, a cool sealing tool for diffs n such is "right stuff" it is the ultimate gasket maker **** never leaks its strong.

cant wait to hear if you notice any differences

gonna hit the dyno to see?