Trans fluid change questions

[Raceaero]

Folks,

My car has 123,000 miles on it and its time to change the trans fluid and I have a couple of questions. Its a manual trans 1997 C4S.

The workshop manual does not specify any differences in procedure between C2 and C4 so I am assuming I just drain and fill to the fill hole.

I read the p-car article about changing trans fluid. It mentions the same issue I had with the car this spring. He had tried several fluids and even a combination of fluids and never really solved the issue. When it is cold (less than 32 degrees F) it barely shifts between 1 and 2 and 2 and 3. It gets better as it warms up and even in the summer never truly shifts great. I am assuming that at this many miles there is some wear.

That said, I need to choose a trans lube. I want to minimize the cold weather shifting issues as much as possible. My choices as I see it are: regular dino fluid - this is what the owner's manual recommends, regular Mobil 1 from the local NAPA dealer, SWEPCO 201, Redline or other synthetic or the Mobil 1 Delvac.

What is the consensus if there is one.

Thanks, Jim

[Don Plumley]

I use and recommend Mobil Delvac SHC which you can get from a specialty oil dealer in Gallon jugs (one is enough).

Remember to remove the fill plug first.

[Raceaero]

Is this the lube? I assume it is good for the limited slip diff.

Product Description

Mobil Delvac Synthetic Gear Oil 75W-90 and 80W-140 are synthetic drivetrain lubricants engineered to meet the most demanding extended drain and warranty requirements. These products are designed for use in heavy-duty drivetrains that require gear lubricants with relatively high viscosity and excellent load-carrying capability and where extreme pressures and shock loading are expected. Mobil Delvac Synthetic Gear Oil 75W-90 and 80W-140 incorporate the latest technology in synthetic basestocks and advanced additives providing significant advantages over mineral gear oils.


The state-of-the-art technology in Mobil Delvac Synthetic Gear Oil 75W-90 and 80W-140 delivers unsurpassed performance for low and high temperature application, protection against thermal degradation and oxidation, reduced wear and corrosion, improved shear stability, extended service capability, and excellent fuel economy. These products meet API service MT-1/GL-5 EP gear oil service classification and perform at the MIL-PRF-2105E level.

The outstanding performance of this product is confirmed by its approval for final drives covered by Eaton Roadranger (E500) and ArvinMeritor Extended Warranties of 750,000 miles, with extended oil drains of 500,000 miles. They are also approved by Mack against GO-J Plus (75W-90) and GO-J (80W-140) extended service classifications.

[aigel]

I used that synthetic Mobil oil in mine after reading about it here too. Not sue what was in it from the P.O. - shifting is excellent before and after change. Being in SoCal, I can't say much about cold weather performance. I could not find it locally and ordered from Lufteknick.

I am no expert in G-50 LSD (unfortunately) but I believe you will need a friction modifier in there for the LSD to work properly.

George

[Raceaero]

So far no one from the cold climates has responded with a recommendation. I was hoping someone from the midwest would say that this oil fixes the cold temp issues.

I don't think it needs a friction modifier as it meets the owners manual GL5 requirement. Thanks all.

[lucittm]

Raceaero,
I just put a gallon of the Mobil-1 Delvac in my G50/52 based on the research I found. Don is right, this is the best stuff for these transmissions. Swepco performs better in the 915 trans, but the internals of the G50 can benefit from the Mobil-1 synthetic. I live in Northern Virginia and I drive my car every day, including snow days. It's not as extreme as Michigan, I know.

Good Luck,
Mark

[bcoats]

+1 on M1 Delvac

[Rick Lee]

Where the hell to buy this Mobil 1 Delvac and do I get 75/90 or 80/140, or both and make some mixture thereof?

[Newsboy]

I switched to Redline 75/90, because the car was a little hard going into 1st gear. it made a noticeable improvement. Remember to do both front & rear.

[Rick Lee]

Front and rear what?

[lucittm]

Try here:
http://www.lufteknic.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=Mobil75-90delvac&Category_Code=

Or, search here for "Delvac"
Lüfteknic - Porsche Parts, Service, Sales, Restoration, Motorsport in Richmond, VA

Good Luck,
Mark