Dock

What is Porsche's recommended oil weight for the 996 Turbo's manual transmission?

tkerrmd

Dock, funny you just posted this question. I was over a friends house recently with the TT. He hadnt seen it since the new LWFW and said hey why is that thing chattering like that!! I proudly told him of my new clutch and fly wheel and he said so why didnt they use Mobil 1 for tranny fluid cause then it wouldnt make that noise?!
Soooooo.......what did the dealer use and what should be or is best to use.
I guess we should ask the clutch experts to tell us the best fluid.....I of coarse ASSUMED the dealer did the right thing.....but now I will check tomorrow

Good question

tom

Dock

Tom -

My clutch noise is slowly getting quieter. The car is in the shop right now getting the clutch slave replaced under warranty. When I get it back I'm going to replace the transmission oil with Swepco 201 80W90 gear oil, assuming the 80W90 is the correct weight.

Even if the clutch noise stays the same, it's worth it for the quicker reving engine.

I searched some of the other forums, and people with lightweight flywheels all report gear noise under acceleration up to about 3000 rpm.

ebaker

In a TSB I found for the 996 Carrera they reccommend 75w90 transaxle fluid, specifically Mobilube PTX and Shell Transaxle fluid. I would not use a GL5 gear oil, it has too much extreme pressure additives for the syncros to work properly. Since the gearbox and ring and pinion share the same oil it might be best to use the exact specified oil. The shop manual recommends changing the oil at 96000 miles.

Dock

Aren't the Porsche recommended oils also GL5?

I've read where Swepco will quiet some of the gear noise that's now present with my new lightweight flywheel.

Dr. T

Hi Dock,
Here's a link to an interesting discussion on renntech Transmission fluid It's interesting how little info is available. I know the tranny in the S2000 is very sensitive to the type of fluid used and after a lot of searching the consensus seems to be GM synchromesh FM. I've searched to see if anyone has done any similar testing with the Porsche but have found nothing....seems the best bet is to go with the Porsche recommended fluid from a dealer.

ebaker

I believe almost all transaxle fluids are GL4. I've read about GM syncromesh fluid solving cold shifting problems on other cars. I believe it's thinner than most trans fluids. I'd worry it wouldn't offer enough protection to the ring and pinion in s Porsche.

Dock

Thanks for the link.

I did ask the dealer several months ago what oil to use, and they said "off the record" that any GL5 hypoid gear oil would work just fine. There was a thread here last year concerning this subject, and the poster (BigApe) said his dealer recommended Swepco, so that's what he used. I also emailed several tuners and asked what they used, and several said Swepco.

This is a subject that seems hard to nail down. I think it may be because not many 996 Turbo owners have changed their transmission oil. I wouldn't change mine right now if it weren't for the gear noise.

ebaker

I believe, as a general rule, GL5 "gear oils" don't go well with syncronizers. Dock, if you use an oil thick enough to dampen noises it will probably not shift well when cold.

Fred R. C4S

FWIW

When Brian Copans rebuilt my 993 transmission, he used Mobil 1 gear lube in the proper weight. He was quite specific about it. He even included the remainder of one liter not used during the rebuild.

As for LWF related gear rattle, I don't think it really matters what gear lube you use, the gears are going to rattle in neutral with the clutch engaged and the transmission warmed up. I can't say I recall any rattle at low speeds under load.

Cheers,

tkerrmd

Know some of my Racer friends are telling me to change the tranny fluid after every few events like the oil and the brake fluid, is this necessary in a car that spends 1-2 days at the track every month?

ebaker

I emailed Exxon's tech support asking if they had a US product to substitute for Mobilube PTX. They replied:
"ExxonMobil does not have a substitute product in the US. The product needs to obtained from a Porsche dealer.

Technical Support Engieer (WJF)"

Michael Ontic

My local porsche dealer was going to sell me the Porsche spec mobilelube....and then admitted that i could use anything.

I've used GL-5 's in 911, 993 and now in my 996TT for years...Sweepco too. I presntly and for several years have been a strict user on Mobil1 products including the full synthetic 75w-90 gear lube.

It doesn't seem to matter what I use. Any difference in noise or shifting is so small i can't tell the differences. I've run several boxes to near 200k miles and have never worn one out or broken one either.

My 2cents worth.
Mike

viperbob

Mobil1 works great. If you have a LWF, you should definitely use it.

Tom - You are correct about frequent fluid changes in the tranny. These cars really heat the fluid. After a few events, you might start to feel some stiffness getting into some gears. I find that after 4-6 events that the fluid can benefit from being changed...

tkerrmd

Thanks Bob, I will follow your advice!