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931 gearbox vs audi transmission

 
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vdub6v  



Joined: 07 Jul 2016
Posts: 29
Location: West Chester, PA 19382

PostPosted: Sun Jan 05, 2020 2:44 am    Post subject: 931 gearbox vs audi transmission Reply with quote

Is the 931 snail shell 5-speed gearbox really that superior to any other gearbox option?

I realize the swap is extensive but in terms of an optimal drivetrain and being a car nerd, is it worth it?

FYI - I have a 1980 NA with 2.0L audi motor and audi trans so it likely will never push more than the stock 115hp
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morghen  



Joined: 21 Jan 2005
Posts: 8177
Location: Romania

PostPosted: Sun Jan 05, 2020 4:25 am    Post subject: Reply with quote

In your case, absolutely not.
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1095
Location: Washington DC area

PostPosted: Sun Jan 05, 2020 8:29 am    Post subject: Reply with quote

Gear ratios are almost identical and parts for first and second are unobtaiium.
There is some weight savings with the snailshell but not much.
The main difference is where the gears are on the shift pattern. On the snailshell reverse and first are to the left. On the Audi, fifth and reverse are on the right. The snailshell shift pattern is called a dogleg.
The reason I run the snailshell on my race car is because you only use first gear in the paddock but on the track you have a workable four speed. The fourth to fifth shift is straight back and the reverse for a downshift. On the Audi box when you shift from fourth to fifth, you have to move the gear lever up, over to the right and up again and the reverse for a downshift. Also, it's easier in an Audi box to hit second on a 5/4 downshift with appropriate wheel lock up, massive over-rev and potential spin. I don't think it's possible to go from fifth to reverse on a downshift on the Audi box but remember that reverse is straight back and beside fourth. Then again....
All the 911 Porsches had a dog leg transmission until 1972 but then went to the Audi shift pattern due to increased torque of the internal geartrain.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1992
Location: MI

PostPosted: Sun Jan 05, 2020 12:34 pm    Post subject: Reply with quote

Maybe if you find a great deal on one, with a torque tube, and I think the rear torsion spring carrier is different for them too,and maybe you find a snail with an LSD, maybe it would be worth it..

I don't think the weight thing is a huge deal, but it also moves the weight more forward in thee rear making the weight it still has more centered.. Can be LSD.. And can supposedly hold all the powers ever..

It's also pretty cool, from a 2nd cool point of view, to have a real Porsche trans..

As far as "optimal" it could be arguable that the 968 6-speed with LSD is more optimal, or not.. Arguable imo..

The snail is also supposed to wear out fast/easy and is expensive to rebuild.. So their are cons too..
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vdub6v  



Joined: 07 Jul 2016
Posts: 29
Location: West Chester, PA 19382

PostPosted: Mon Jan 06, 2020 12:57 am    Post subject: Reply with quote

I've got the complete drivetrain, torsion tubes and all.

It's not an LSD diff


In order of priorities, this swap is something that I'm going to do soon. Either sit on the parts or send them down the road.

https://drive.google.com/file/d/11_RqfPp8pr2-wRPW3yYb3v_yG3mBl18I/view?usp=drivesdk[/img]
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1095
Location: Washington DC area

PostPosted: Mon Jan 06, 2020 3:17 am    Post subject: Reply with quote

On my race car, I welded up the spider gears in the diff to give me a total locker.
I did the same on the Audi box in my first 924 racer but it was harder to do because you have to take the tranny apart to get the diff out (input shaft interferes) meaning you have to pull the gearbox out of the car. Snailshell diff falls out when you pull the side plate.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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