Question about tranny oil

[green71]

Hi all,

At the recommendation of a reputable local Porsche mechanic, I changed my tranny oil from Valvoline (or was it Havoline?) Heavy Duty 80/90 to Mobile 1 Synthetic 75/90. Two things I noticed w/the new gear oil:

1. My car's traditional nicking of reverse when shifting from first to second when cold seems to have disappeared.

2. When shifting from third gear at high rpm(>3000rpm in third) down to second gear, there's a pretty loud grind/crunch ("grunch"). The grunch doesn't occur at lower engine speeds. I never noticed this before.

My question: is it possible for this change in tranny oil to alter the performance so much? Or is it more likely, in the case of #2, that I just never noticed it before? (Generally, I don't drive it that aggressively. But I THINK I would have noticed the grunch before . . .)

What's your experience been?

TIA,

Mark

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1971 1.7l 914

[Jim Smolka]

I recommend SWEPCO tranny oil available from Pelican.

[scotty914]

some say the moble one is to slippery for our synchros but it is good for the shift linkage evidensed by letting it slide to second better


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scott thacher
75 1.8 on the road again
75 under rust
(fine german rust)

[This message has been edited by scott thacher (edited 09-19-2001).]

[toman]

I don't know about the Mobil 1 synthetic, But I've been using the Redline for about a month now and I love it. My transmission works better in every way.

[Dave at Pelican Parts]

I think that the not nicking reverse is a coincidence. And that you can affect that even more by mucking with the shift linkage, or by shifting slower and more carefully.

The "grunch" is you trying to get the car into gear before the synchros have a chance to match the revs of the gears and sliders. There is a decent chance that the Mobil-1 is exacerbating that because it is keeping the synchros from having the friction the way they should.

This is supposedly not uncommon with synthetic gear oil and 901 or 915 transmissions.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

[green71]

Dave,

I think you're right about nicking reverse; that symptom returned this morning when the engine & tranny were dead cold.

I've searched the BBS for tranny oil & Swepco posts; seems like members here prefer Swepco nearly 5:1 or more. I'm going to go w/the Swepco & see how that treats me.

Thanks,

Mark

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1971 1.7l 914