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YOUR RESEARCHMy 90K service
Leading reported evidence
Use boat transom plug
Performed · outcome unconfirmed
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Performed · outcome unconfirmed · Original poster
I used a boat transom plug to remove the spark plug tubes.
Leading evidence: 'Use boat transom plug' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Fill plug' (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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Suggestion
Make sure you don't over fill the tranny, it doesn't work right when it is overfilled.
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Suggestion
The front differential oil was like new, don't recommend anyone wasting their time replacing the front differential fluid on their C4 anytime soon.
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6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261027T000231Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I have a '99 C4, 89K miles. The service for 90K includes spark plugs, rear and front transaxle fluid, air filter and a bunch of inspections. I decided to do this myself.
Here was my experience:
Spark plugs- not that hard, space is very limited and I spent more time bending and contorting to get a good angle to twist and turn the bolts. Allow maybe 5-8 hours your first time as it is very tedious and many breaks are necessary.
I found one cracked ignition coil and another ready to crack. Also there was some oil seeping out of 3 spark plug tubes. I ordered 6 new coils and the spark plug tube gaskets from Sunset- a few days delay for shipping.
I used a boat transom plug to remove the spark plug tubes. Again space is very tight and it was tedious to keep trying and trying. On my car (3.4L engine) the spark plug tubes can be removed without removing the spark plugs.
Now I am ready to put it all back together and I lift the car by the engine lift point. I get the dreaded puddle- the engine mount split. I am in the camp that says it was a matter of time as engine mounts are wear items. A call to Pelican Parts gets 2 new engine mounts on the way. A few more days delay. Engine mounts are an easy DIY.
The draining of the rear transaxle is easy and straight forward. The front did not go well. I rounded off the fill plug. It took 2 weeks to get a new plug as the only source was Porsche in Germany. I ended up having an indy shop get the rounded plug out. I went with porsche fluid.
Other hints:
If you do this on jack stands like I did, wear safety glasses. Stuff will fall in your eyes. When you screw the spark plugs in, tape the socket to the extension.
After all of that I have not noticed any huge difference in the car. Gear whine decreased some but everything else is about the same.
Hope this helps as guys start to see 90K.
Just did the 90k on my 996 too.
The front differential oil was like new, don't recommend anyone wasting their time replacing the front differential fluid on their C4 anytime soon.
The front differential casting is not as clean and causes interference from using a box end wrench. I grinded some of the casting material off first with a Dremel.
Make sure you don't over fill the tranny, it doesn't work right when it is overfilled. I believe it only needs 2.5 liter
