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Discussion summary
YOUR RESEARCHHow to rebuild the 996 rear differential
Reported or suspected cause
created by the front bearing (the big one
Reported cause
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1
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Reported cause · Original poster
The problem was created by the front bearing (the big one near the cowling), as shown on this picture (the cover of the bearing).
Leading evidence: 'created by the front bearing (the big one' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'created by the front bearing (the big one' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check gear lash' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Replace diff oil, there was enough debris in the plug
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Performed · outcome unconfirmed · Original poster
When I changed the diff oil, there was enough debris in the plug.
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Suspected cause
If the Side carrier bearing are NOT the cause, and the cause is the "ring & pinion gears" ..
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Suggestion
But the most common causes of noise would be the side carrier bearings that could be replaced without total Trans dissasembly.....just remove the center carrier/ring gear and inspect the side bearing for pitting...
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Hello,
My car(996.2 3.6 2002 Carrera 2 Coupe Tiptronic) has 300k km on the clock and the differential is whining after around 80 km. I tried using a 75W90 oil and some additives but the whine is there so a rebuild is required.
What parts should I be changing instead of buying a second hand or a new rear differential? Can you guide me to the part numbers?
BONUS TO MY FRIENDS @ RENNLIST:
The best site to find diagrams and parts for all Volkswagen group including Porsche is the following:
https://ifinterface.com/page/page3.php?langid=1
Please use this site to see the diagrams and the parts it also includes replacement parts and it is well updated.
Click on the link CarProg2.
Thanks,
To help progress with the answers, I am attaching two diagrams. Should I go for number 1 on the first diagram, or 1 or 2 on the second diagram? What usually wears after 200k miles? When I changed the diff oil, there was enough debris in the plug.
Or 1 or 2 or both on this diagram?
Bearings are 5 and 6 on the second diagram. Shouldn't I be worried about gears and wear after 200k miles? Is there a safe way to test them? Is there an easy way for 996s to check gear lash?
It's the transmission bearings that usually start to make the noises not the diff.
Edit: Sorry see its a tiptronic, I don't have any experience with those.
Please ignore my original post. I took the pictures to be from a manual transmission, and my original comments (below) were wrt. a manual box.
I would not be too quick to assume that it's the diff carrier bearings rather than the (notorious) pinion shaft bearing, for example. Tear-down will shed light.
If you do decide to replace an open differential, get a later four-spider version rather than the earlier two-spider version. Latter is notorious for tooth erosion and breaking.
Isalos, I don't want to sound rude or discouraging. But from your questions, I am pretty sure you're over your head on this project.
No offence taken. I am trying to help my Indy on the diff. The sound I am getting is typical diff sound, had it in other cars such as Touareg, Q7, Z3 and even on an old sj410. Before we dismantle it, I take opinions from the community.
I am also thinking of replacing it with an LSD...
The Tiptronic differential is not a DIY friendly unit...It uses the Mercedes 722.6 Transmission...and is a Specificity field that most Tech's don't venture into..
But the most common causes of noise would be the side carrier bearings that could be replaced without total Trans dissasembly.....just remove the center carrier/ring gear and inspect the side bearing for pitting...
If the Side carrier bearing are NOT the cause, and the cause is the "ring & pinion gears" .. then total dissemble will be required and special tooling is need to properly set up the gears...
Note : the Pinion Bearing failure that is so common on the 6 speed does not apply to the Mec 722.6 Trans..
this is the final angle of attack. Change the two conical bearings number 5,6 on the diagram above and at the same time inspect the gears. If the gears require replacement, a merc specialist will handle from then on.
One question though; can the bearings be changed while the trans in the car? Doable or no space?
Porsche does not list a service kit for the G96 LSD in their parts diagrams, unlike the LSDs used in the 993 and 964 generations. I haven't been inside a G96 LSD in a while and cannot say whether the 993 kit might work. However, my experience (not unique) has been that the factory G96 LSD is a) weak to begin with, and b) wears out quickly. With that in mind, I would normally recommend one of three avenues:
1. If you are driving your car just on streets, live with the worn out LSD. You won't notice a difference, especially given its low lock-up.
2. If you autocross or drive on-track, replace the internals with a complete stack from Guard transmission. You'll get an LSD that does what one should, and it won't wear out soon.
3. Buy a Guard LSD.
I've done (2.) for customers, they have been pleased with the result, and it is less expensive than popping for the complete Guard LSD. Hope this helps,
Kevin
Hello,
We managed to find some time and work on the whining noise on my differential. The car is a C2 tiptronic 3.6 (996.2) with the A9610 Mercedes gearbox.
The strange thing to note is, that for this gearbox (or any other Tiptronic) no part numbers for the differential are given in the diagrams, please prove me wrong (I need to be proven wrong). Here is one diagram, which does not show any part numbers.
https://nemigaparts.com/cat_spares/p...996/21/320030/
Anyway, it is serviceable, and this is how we did it:
1. Remove the parts from the right rear wheel and lower the engine from the front of the Tiptronic gearbox
The side parts are shown below. If you remove it like this, no wheel alignment will be needed afterwards.
2. Open the cowling and remove the differential by hand.
3. Inspect and if all good (almost good in my case), replace the two bearings, with the part numbers shown below (ONLY FOR TIPTRONIC):
A) LM806649. My car had a bearing my Timken, as shown in this link:
https://gr.rsdelivers.com/product/timken/lm806649...
. This part is
nowhere
to be found on Porsche diagrams.
B) 99905906602. I got this from Porsche.
https://www.rosepassion.com/en/99905906602...
Remove and replace using the appropriate tools, no special guidelines are needed here...
Replace the o-ring 99639700500 (Number 5 on the NEMIGA diagram above).
Replace the seal 99911334741 (48x68x10).
Both these parts are sourced by Porsche, the latter is made my KACO.
Clean the cowling and the differential case with brake cleaner. Below shown cleaned:
I added MOTUL GEAR 300 75W90 (
https://old.motul.com/gr/en/products/gear-300-75w90
) with some MOTORKOTE in it, as I usually do in all my differentials (cars/boats).
The result
: Whining noise went down by 80%, only slightly apparent around 70-90km, and goes away after 100km.
The problem was created by the front bearing (the big one near the cowling), as shown on this picture (the cover of the bearing).
This created misalignment and vibrations that had an effect on the teeth of the differential. A simple problem that could have been avoided if the bearings were replaced earlier.
My advice
: If your car has more than 100k miles (160k KM), do the replacement of the two bearings. Easy job by a mechanic, 4-8 hours max.
Hope it helps somebody.
This is amazing @isalos, thank you.
Would a similar bearing be found on a manual transmission diff? I have some whining and would like to replace it if possible when swapping my subframe bushings.
^^^This If you want an LSD. I have been running option (2) since the late 2000s. Just had a few internal parts refreshed 2 years ago. This option is well worth the money of you want a Guard LSD.
ivansskoro, On post #2 of this thread, second diagram you need items 5 and 6, these are the bearings you are looking for.
Part numbers:
999 059 066 02
999 059 064 00
https://nemigaparts.com/cat_spares/p...996/21/305020/
Thanks for the great writeup
@isalos
!
Got all the parts and the B) bearing from Porsche today, reverse searched it and it�s
TIMKEN NP715284-NP106970
, which can be sourced at any technical supply shop for 1/4 of the price the big P asks....
Also, have you given any thoughts/measurements/adjustments to the spacers that sit in the diff cover? Anybody got an idea where to source those??
thanks
they are different bearings left and right, hence the different parts numbers; but definetely no need to buy at Porsche.
Timken:
LM806649/LM806610
and
NP715284/NP106970
My diff (or transmission) was still noisy after the change btw 😩 Does anyone have the bearing types for the pinion shaft?
