Re: 4K tranny - .75 or .80 5th??

[drew <drew@dyermaker.cs.uoguelph.ca>]

I run a .71 over 3.94 in my 84 - in a factory 7A (AKA 4+e) box.  It works
out very well for me, as I enjoy the longer legs for commuting.
Admittedly, I don't race or autocross, but on those rare occasions when
there's not enough grunt to pass in 5th, I downshift - that's what that
pedal on the left is for... :)  I have a more or less stock JH, with an
"N" cam (soon to be a G), 4-2-1 manifold, and have the cam and ignition
timing dialed up so that 1700-3000 is fat.

The big drawback to a .71 in a 4K (let's forget the 9A, as .71 + 3.67 is
for TDIs or VR6's, thank-you very much) is that the gap between 4th @ 1.13
and fifth at .71 would be a bogger.  If you're seriously considering a .71
fifth, I'd take a good look at the 7A, which came in most late 83 and 84
gas or diesel rabbits, jettas and pickups.  It's pretty easy to spot these
boxes in the wreckers, as they usually have a 4+e gearshift knob (ie 5th
is actually marked as E, which stands for whatever the german word for
economy is...).

Years ago I put a .75 fifth gear kit in my 92 Golf diesel, which had a
very close ratio gearbox (fourth was 1.13, fifth was .89, final was 3.94).
The resulting gap between 4th and fifth made for uncomfortable driving.  
I agonized over the decision for weeks, and actually wrote a quick and
dirty basic program to simulate engine and road speed based on tire and
gear ratio - it allows you to row up and down through the gears to see
what your favourite shift points will result in.  I can post it on
anonymous ftp if anyone's interested.  Tire size and transmission ratios
are in flat text files, so it's easily modifiable to suit your needs.  It
comes with the standard VW transmissions and common tire sizes already.

Here's the 2-5 and finals for the 4K, 7A and 9A boxes.  Notice that the 7A
in fourth is the same as the 4K in fifth - which is great for me, as on
those rare occasions when I want to hit top speed, I still can in 4th...

-------2----3----4----5---FD-
"4K" 2.12 1.44 1.13 0.91 3.94
"7A" 1.94 1.29 0.91 0.71 3.94
"9A" 2.12 1.44 1.13 0.91 3.67


Drew (84 Wolfsburg Edition)


On Tue, 23 Jan 2001 thescirocco@juno.com wrote:

> On Tue, 23 Jan 2001 02:16:54 -0500 "RoccoPhil" <roccophil@mindspring.com>
> writes:
> > I have heard some rebuilders (Stu from BSI for one) that the .71/.75 
> > is a too huge a drop for a 3.67 (course I am talking about the 9A
> here).  
> > So for an AGB or equivalent 3.67 I was considering going with a .80 5th
> 
> > gear.
> The .71 is a bit much with a 3.67 final gear ratio...
> 
> > My question - if I spring for a 4k instead, is it advisable to do 
> > the .75 as opposed to the .80 due to the 3.94 final?
> Yes, I'd even think about a .71 5th gear.
> I think the 4K is 3.89:1, though...
> 
> Ask yourself, do I want an overdrive 5th (.71), or a closer ratio 5th,
> (.75).
> 
> I'm deciding between .71 and .75 for my 3.94:1 2H, and I'm leaning
> towards the .71 5th gear, out of my RIP '81 S.
> 
> With 3.67:1, I'd use the .75 or .80 5th gear.
> With 3.89 and 3.94:1, I'd use a .71 or .75 5th gear.
> ...Depending on if I want an overdrive 5th gear or not.
> 
> Peter
> '79 Scirocco 16V project car
> '83 GTI "Caged Rabbit" 
> '84 Scirocco, RD/FF
> '80, '88 Scirocco rollers
> 

Drew MacPherson, Network Analyst, University of Guelph

drew@dyermaker.cs.uoguelph.ca           |  visit the Massey-Harris page:
http://dyermaker.cs.uoguelph.ca/~drew   |  http://m-h.cs.uoguelph.ca


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