Transmission noise after gear oil change
 

2006 987.1 base boxster 5-speed

Changed transmission oil and now there's a 'krkrkrkrkr' sound during low ( <1k) rpm when accelerating. Above 1k I don't hear, probably due to engine being louder. Seems to be happening in at least 1st, 2nd and 3rd. No noise when in neutral. It's not very loud but definitely there. You can hear it best at around 11-13 seconds in the video:

https://streamable.com/pqx2k1

Used this oil:

I'm considering adding more oil but not sure that will help as the level seems within spec. I checked the level with a bent paper clip and it was within 2-3mm below the opening:
https://cimg8.ibsrv.net/gimg/rennlis...6ec819887a.png

The sound was not there before the change. Found couple of places on the web mention that during the change, there's a possibility that some particles get washed down/stuck/etc in new places which could cause the rubbing/noise. Anyone run into a similar issue?

How much of the gallon jug did you use?

Might consider buying 4 liters of the Porsche 75W90 gear lube, and redo.

https://cimg7.ibsrv.net/gimg/rennlis...9a72a8de55.png

Looks like 3 quarts (2.8 liters) was used with 1 remaining in the jug.

If was sure that the noise is from the transmission and as a result of the fluid change, I think I'd be tempted to go on a lengthy run to get the fluid good and hot and flush it again. If your theory is right that debris got lodged somewhere, perhaps a good hot flush might dislodge?

If there was a difference in the noise after the gear oil change I'm not quite sure how to explain that. But If you're literally accelerating the engine on the road from 1K instead of downshifting then you're lugging it, so I wouldn't be surprised if it made some weird nosies. Maybe don't do that.

​​​​​​Probably didn't explain it clear enough. Basically once in gear, any light acceleration causes the noise. As long as the car within 1k RPM, I can hear it. So, doing 5-10mph.

I'll definitely consider doing another drain in hopes of clearing whatever may be causing the noise. Perhaps get the Porsche 75w-90 this time.

Can transmission be flushed with some inexpensive liquid? What do the shops use if such service exists?
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That's an excellent question. But I would want to hear the answer from a well reviewed Porsche Indy shop. A place that makes its living servicing and repairing these cars everyday out of warranty.
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Matt from GT Gears had advised me not to use anything other than the Porsche gear oil for the 987 although it was more related to proper synchro operation. I would definitely drain out the fluid and put the Porsche fluid back in.

There is nothing wrong with Delvac. Came recommended to me by one of the best trans shops in the country. Been using it in my 993 and Cayman race cars for 10 years.

That said, I've never driven these cars on the street or with whatever the factory fills with, so maybe its a little more noisy???? No idea.

Oddly I'm in the middle of changing mine today too.
https://cimg5.ibsrv.net/gimg/rennlis...7eff4c77e1.jpg

As Jeff said, Devlac is a great oil. I am pretty sure it was used in all factory Cup cars at one time. That said, it does have a friction modifier so it is compatible with LSD trans-axles. So, IMHO, reverting to standard Porsche oil might be a good idea.

Just to make sure, Mobil 75W90 Gear Lube is not the same as Mobil Delvac 75W90 Gear Lube. Make sure Amazon sent you the right stuff.

I just change my gear oil on a 2008 Boxster base model (5-speed). Note that the correct oil level for the 5-speed is 11mm below the lower edge of the fill hole, not 2-3mm. That may be the source of your noise.
(I used Porsche oil and filled to 11mm below, and no noises present.)
Since the fill level can be confusing depending on where your read about them, I checked the old oil fill level and it was as 11mm below the lower edge. The 5-speed takes 2.25 liters per spec (I was able to get 2.2 liters in, some likely didn't drain out).

Huh you may be unto something here. 2.8L is capacity for a 6-speed. Perhaps subconsciously I just wanted to make it an S. I'll attempt to remove ~0.6L and see if that makes a difference. Good call.

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I don't know why you're suddenly getting that noise, reading through this thread. Mobil 1 LS 75W90 or Delvac is fine, they are both quality fluids that I recommend to my customers. The Porsche fill is (currently) Mobil PTX, which is not available in this country except as hella expensive bottles from Porsche or a few Porsche suppliers who are importing the stuff. The fluid is not the cause of your noise. Yes, for the Boxster five-speed, 11 mm below the lip, but this also is not the reason for your noise.

How many miles on your car / transmission? I am not sure what noise I am listening to in your video.

Got to it yesterday. Removed about 480mL which got me past 11mm point. Added 50mL back. Sitting at about 11mm mark now.

Went for a drive and the noise was still there.

Car has about 68k miles on it. I'll see if I can get a better audio/video of the noise.