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99 C4 Gear and transaxle oil choice questions

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1 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCH99 C4 Gear and transaxle oil choice questions

Leading reported evidence

Replace transmission gear oil

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
So I want to change the transmission gear oil to see if it would make any difference, along with the motor oil.
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Read full discussion summary

Leading evidence: 'Replace transmission gear oil' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace transmission gear oil' (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.

Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.

Read captured replies

1 matching discussions · 1 captured posts examined · 0 partial discussions

Compare 4 other evidence results

Use 1.5 liter (can someone verify?)

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
Front transaxle uses 1.5 liter (Can someone verify?)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use 15w50, i want

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
(Previous owner have been using 15w50, I want to change to 0w40)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use 3 liter (can someone verify?)

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
Transmission/differential uses 3 liter (Can someone verify?)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use a/c in california

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
(Yes, still using A/C in California today).
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Frequently discussed actions (7)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Replace transmission gear oil

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
So I want to change the transmission gear oil to see if it would make any difference, along with the motor oil.
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use 1.5 liter (can someone verify?)

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
Front transaxle uses 1.5 liter (Can someone verify?)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use 15w50, i want

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
(Previous owner have been using 15w50, I want to change to 0w40)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use 3 liter (can someone verify?)

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
Transmission/differential uses 3 liter (Can someone verify?)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use a/c in california

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
(Yes, still using A/C in California today).
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use oil

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
I need to use oil that will protect both the differential and provide enough friction for the synchros to work since the unit in the 996 is a combined unit in design (Thus share the same fluid)
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Use same ptx oil or just standard transaxle oil

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
Also does the front transaxel uses the same PTX oil or just standard transaxle oil.
Original post Read captured discussion
99 C4 Gear and transaxle oil choice questions

Coverage and how to read this overview

Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.

1 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

Rennlist: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261027T044418Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

Hi guys, My first post on the 996 side of the board. Bought an used 99 C4 couple month ago been enjoy driving it so far, much effortless to drive compare to the 993 and A/C works great. (Yes, still using A/C in California today). So far knock on wood everything seems to be in the working order except some small interior noise and minor exhaust rattling sound. But I really don't like the way the transmission shifts. Especially when it is cold. It is almost impossible to shift to first gear unless the car is stopped completely for few seconds, and very notchy going to 2nd. Once the car is fully warmed up it is butter smooth. So I want to change the transmission gear oil to see if it would make any difference, along with the motor oil. (Previous owner have been using 15w50, I want to change to 0w40) I have been checking the archive and also browsed the Renntech board, and this is what I have gathered so far, just need some confirmation from some of you that have some experience with this. This is what I know so far: (1). I need to use oil that will protect both the differential and provide enough friction for the synchros to work since the unit in the 996 is a combined unit in design (Thus share the same fluid) (2). Mobilube PTX (synthetic) 75W-90 GL-4, GL-5 is what the factory recommends (3). Can't get Mobil PTX here unless you want to pay outrageous price from the dealer. (4). Transmission/differential uses 3 liter (Can someone verify?) (5). Front transaxle uses 1.5 liter (Can someone verify?) (6). Someone recommended using Silkolene Silktran SYN 5 API GL4/5 75W/90 as a substitute, which is available in the US for $15 / liter. Have anyone tried this? Just curious if I am on the right track? Also does the front transaxel uses the same PTX oil or just standard transaxle oil. The shop manual is also not too clear on this subject, so I want to ask the board to see if anyone can shine a light on this subject. TIA

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