15 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHWhen to change gearbox oil
Leading reported evidence
Replace 35,000 miles / 18 years ago
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Read evidence and context
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Performed · outcome unconfirmed · Original poster
Looks like it was last changed 35,000 miles / 18 years ago.
Leading evidence: 'Replace 35,000 miles / 18 years ago' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check things as i go it’ll eventually show itself' (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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Performed · outcome unconfirmed
My indie advised me to source a good used box which I did.
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Performed · outcome unconfirmed
I couldn't find any used boxes in UK so had to source from Germany.
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Suggestion
Its one of those noises, systematically checking things as I go it’ll eventually show itself ..
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Suggestion
As usual make sure you remove the fill plug before attempting the drain plug..........for obvious reasons.
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Suggestion
Agree with the post that said every three years, gearbox and diff rebuilders will also quote the same, and if the car is used on the track, every two years.
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15 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
911uk: 1 discussions
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Generation: 20261026T113718Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Looks like it was last changed 35,000 miles / 18 years ago. Is it worth doing this ? Seems like it can't hurt. Motul 300 75w90 I'm thinking.
There is a slight whine when I lift off the accelerator, but that might well be normal for all I know!!
Deffo do it. Think I do mine about every 3 years / 30k miles. Often gets overlooked by most car owners and there's oil in there for a reason. As usual make sure you remove the fill plug before attempting the drain plug..........for obvious reasons.
I had mine changed in Dec 24 , purely out of maintenance interest. Didn't notice a difference as the gear change was lovely anyway. The whine is a characteristic of the 3.4 engine. Always worth getting it done I reckon.
And if you want even better cold shifting get something with a lower viscosity at 40°C like the original Mobil PTX, that Porsche factory would have filled it with, or Castrol Transmax for Manual Transaxle or at least below 80 mm2/s (also called cSt - centi Stokes)
I changed mine simply to get a fresh known starting point once I'd bought the car. Managed to get just the necessary 3 litres of Shell Spirax S5 ATE 75W-90 GL-4 GL-5 which I believe is an OE option designed for our transaxle, similar to the Mobil PTX. Have to say it made a big difference to 1-2 smoothness when cold, got rid of the graunchiness almost entirely. Also put in one of the yellow Powerflex gearbox bushing inserts at the same time which I am sure contributed to the overall improvement with zero additional nvh in my case.
Mine has a whine noise I can’t place, I haven’t ever driven another one to compare.
I read the CLR thread recently and the chap mentions a known gearbox bearing failure
I think it’s Gearbox / its motion related. It’s faint but it’s there.
Its one of those noises, systematically checking things as I go it’ll eventually show itself ..
Agree with the post that said every three years, gearbox and diff rebuilders will also quote the same, and if the car is used on the track, every two years.
The whine is often the start of the pinion bearing starting to wear. Mine was done at 120K miles and it was badly pitted by then. I trieda gearbox oil change first, but the whine remained. Quite a few write up's on here. I removed the box and took to Helical Gearboxes (I think they were called) in South London. Quite a job on the drive on stands. Expect £1,500 upwards to get a loose box rebuilt. The bearing (which is the output shaft one to the diff) is a lot of money to buy, I seem to remember £800 ish.
This
996 manual gearbox is a known weak point but not really discussed much. I wasn't aware when I bought my first 996 around 8 years ago. I didn't necessarily notice the whine but the box failed. Watching videos I have of pre gearbox fail I can now hear the whine.
If you're lucky it will just be bearings which fail or get noisier - not sure. Mine was more than that. It started refusing to go into gears and just became problematic.
When I started discussing the failure it soon became apparent from many others who had been through similar that the boxes in these are known for this. And its a sort of well known secret they will fail eventually. I wish I'd known that before I bought the car. I'd assumed simple manual gearbox should be pretty robust as it is with most other 2nd hand cars.
My indie advised me to source a good used box which I did. Because replacing the worn 'part' - not sure I can remember it's name pics below - inside was more expensive that sourcing a used box. I couldn't find any used boxes in UK so had to source from Germany. Which kinda confirmed they're in demand because they fail.
I commented about this known weak point on a 997 thread where someone replied saying this was not the case with the 997 as it had a different box made by a Japanese manufacturer. And I was led to believe the 997 box is no where near as troublesome. I don't know how true that is. Some people have since started investigating the possibility of using the 997 box on their 996 as there are more available to buy used. Go ahead and do a search and see for yourself. Of course this could be more to do with the numbers of 997 sold being much higher than 996.
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