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

[Shawn C Meze <skerocdriver@juno.com>]

On Tue, 23 Jan 2001 16:04:48 -0500 "RoccoPhil" <roccophil@mindspring.com>
writes:
>My surmising at this point:
>
>If I stay w/ an AGB I'd add a .80 fifth
>If I stayed w/ a 9A I'd add a .75 fifth
>If I had wads o' money, I'd construct a 4k w/ an .80 fifth and .71 
>sixth.
>Does that sound like a hot tranny or what?
>
>-PK


OK, heres the deal. The bottom line is it all depends on what you want
out of the gear for your particular car. 
Do you want ultimate fuel economy on the highway?
Do you want the best gearing for your power output?
Do you want all out 0-100 mph racetrack gearing? 
Do you want a combo of all of the above?

Choosing one gear over another is a total tradeoff. Without the benefit
of a 6 speed tranny, which many cant afford, you cant have it all. 

What I can tell you is, I have a 4K tranny in my 86 Jetta with a .71 5th
gear installed. The shift from 4th to 5th is a 1500 rpm drop. This means
that getting on the freeway you need to rev out 4th a little bit so the
5th gear exchange doesn't drop you too low in the rpm band. The motor is
tired and completely stock except for the 260 cam, kent timming gear and
exhaust work. The benefit is the motor turns a low 3200 rpms at cruise
speed. This helps the motor to run cooler while getting the best fuel
economy possible. I get 28-35mpg in this car where before I would never
see anything over 26mph on its best day. 

In my 82 Scirocco I have a 2H tranny with a .71 5th gear and a quaife. On
the track the 5th gear absolutely sucks! The drop to 5th gear kills the
speed on tracks which necessitate a 5th gear. Since this was meant to be
an autox car, the close ratio tranny is the best choice while the 5th
gear is for the benefit that the motor turns a low 3200 rpms at cruise
speed. This again helps the motor to run cooler while getting the best
fuel economy possible. Especially since I do drive 2+ hours to all the
events I run year round. The motor has enough power to drive 5th gear up
almost any hill so the tallness of the gear isn't a problem in the
Scirocco like it is in the Jetta. if I were to do alot more open track
events I would definitely put the stock .89 gear back in and go with it.
Since that's not the plan right now, it will keep the tall 5th gear or at
the very least, give up some of the tallness for a .75 or .80 gear. 


Shawn Meze
86' Jetta GLi 8V       84' Scirocco 8V           88' Corvette "SS"
82' Scirocco GTi -FSP 30-   79' "Project FSP Scirocco"
The Fastest, Quickest, Cleanest and best looking Scirocco in all of San
Diego!
http://www.Geocities.com/MotorCity/Speedway/1308/index.htm

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