Limited Slip

Va_Powerman · 03-20-2013, 11:09 AM

So, I had not changed the trans fluid changed in the '85 ROW (german market) 911 since I'd owned it, so I took it to the local bmw/porsch/merc shop. I believe that the tech installed OEM fluid without L/S conditioner. Now I've got a bit of gear whirring type noise.

(he also indicated that the fluid looked like it had been in there for a while...)

What would be a recommended course of action, and how quickly does this need to be addressed?

Thanks...

Steve@Rennsport · 03-20-2013, 11:28 AM

Hopefully, they used Swepco #201 gear oil and NOT a synthetic in that 915 transmission. I would also confirm they filled it completely, to spec.

Do NOT delay here; immediate resolution is needed to prevent any damage.

BE911SC · 03-20-2013, 11:37 AM

The first servicing I did immediately after I bought my LSD-equipped '84 was to drain the fluid and put in Kendall 80/90 with LSD additive per Pete Zimmerman's recommendation. Shifts better and is quiet.

Va_Powerman · 03-20-2013, 11:40 AM

Thank you.

I just spoke to them, and it was a Bilstein synthetic product that they tell me is the factory reccomended fluid. It did not have the L/S conditioner.

They are willing to replace it asap - they just need to source the correct fluid.

I understand that there is an ongoing discussion on the Kendall -vs- Swepco 201 Multi-Purpose Gear Lube; at this stage of the game, should I go with whichever is available?

Andy911sc · Andy911sc's Garage

I would go with the Peter Zimmerman recommendation, plus you have BE911SC's review of it. That would probably save you days from people back and forth spinning your head around.

Matt Monson · 03-20-2013, 12:24 PM

Quote:

Originally Posted by Va_Powerman

I understand that there is an ongoing discussion on the Kendall -vs- Swepco 201 Multi-Purpose Gear Lube; at this stage of the game, should I go with whichever is available?

Yes. I manufacture gears for a living and find this anti-Swepco movement ridiculous. Both the gear oils mentioned are excellent products that will work well in your 915 gearbox.

Va_Powerman · 03-21-2013, 04:29 PM

Can someone explain to this newbe why no synthetic should be run in my 915 gearbox?

It seems that if its the correct weight lube, with the correct characteristics and L/S additive, it should be ok; but what am I missing?

Thanks...

HarryD · 03-23-2013, 11:24 PM

Quote:

Originally Posted by Va_Powerman

Can someone explain to this newbe why no synthetic should be run in my 915 gearbox?

It seems that if its the correct weight lube, with the correct characteristics and L/S additive, it should be ok; but what am I missing?

Thanks...

I has to do with the synchronizers. The 915 box uses a Porsche design synchronizer that is different than the Borg Warner style used in most other boxes. It needs a bit of friction to operate properly. Synthetic gear lubes are too "slippery" for the synchronizers to work properly.

If you want to learn more about the 915 transmission, look for posts by Grady Clay on the subject. Several years ago he did some excellent commentary.

atc_marty · 03-24-2013, 08:41 AM

Side note: is the L/S additive necessary for G50 LSD-equipped cars? I know the G50 uses something synthetic...

GaryR · GaryR's Garage

I can attest to the Kendall 80/90 LSD product (no additive needed) in use under race conditions, transmission has held up at least as well as when I was a Swepco guy, if not better.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by atc_marty

Side note: is the L/S additive necessary for G50 LSD-equipped cars? I know the G50 uses something synthetic...

Use the stuff on the left in g50s the stuff on the right in 915s, no additives in either

Matt Monson · 03-24-2013, 09:07 AM

Quote:

Side note: is the L/S additive necessary for G50 LSD-equipped cars? I know the G50 uses something synthetic...

An LSD additive is not necessary for any gearbox. LSD additives make the LSD slip more. It is designed to make them run more quietly and with less chatter. Using one or not is a personal choice.

I tell my motorsports customers not to use an additive if they want their LSD to have the most bite. My products run fairly quiet and smooth because of our unique clutch design. So even in a street rod, at least with our LSD it is not required.

atc_marty · 03-24-2013, 10:22 AM

Great, thank you gentlemen.