[Vwdiesel] Rabbit Shift Points

[R. Brown]

Bryan K. Walton wrote:
> I've been trying to figure out where the optimum shift points are on
> my '84 Rabbit with the 4A four speed transmission in order to help
> maximize my fuel economy.  I have an upshift light that comes on
> at various speeds but I'm not sure exactly if it is coming on at
> the correct time. The reason I question whether it is functioning
> correctly is that it used to light up at the following speeds:
>
> Shift into 2nd at 9mph
> Shift into 3rd at 18mph
> Shift into 4th at 27mph
>
> I noticed that when I shifted at those speeds, the engine sounded like
> it was lugging (especially when shifting into 4th).  Then, in January
> I replaced my injection pump and set the timing to be within spec, but
> retarded.  I got everything back together and noticed, bizarrely, that
> my upshift light was now coming on at different set of speeds!?  It
> now lights up as such:
>
> Shift into 2nd at 14mph
> Shift into 3rd at 25mph
> Shift into 4th at 37mph
>
> Using these shift points, the engine definitely is not lugging. 
> But now I wonder if I'm shifting too late -- if the RPMs are getting
> too high.  I don't really know.  My guess is that these points are
> closer to being correct.  The gear ranges listed in my owners manual
> seem to coincide more with how the upshift light is working currently.
>
> 1. Can anybody suggest how changing the IP and its timing, could
> possibly affect when the upshift light comes on?
>
> 2. Can anybody tell me at what speeds the upshift light should turn
> on, with a 4 speed transmission?
>
> 3. My speedometer has some "dots" on its face at various speeds.  
> Specifically, the face has 1 dot on it at the 23mph line.  It has 2
> dots on it at the 43 mph line, and it has 3 dots on it at the 68 mph
> line.  Can anybody tell me what these dots mean, if anything?
>
> Thanks!
> Bryan Walton
>   

Upshift light works off of the alternator (w-terminal) signal and on my 
'82 comes on about 2400 RPM.  Also affecting it are the two throttle 
switches (open and closed) and the top gear (4th or 5th) switch to turn 
off the light in top gear.  Maybe the alternator belt was slipping or 
the throttle switch adjustment was changed with the pump.  As far as I 
can figure, the dots on the speedo are sort of a "redline" for a given 
gear.  You could work back to find speeds and RPMs given the trans ratios:
    http://www.4crawler.com/Diesel/VW_020_transmission.shtml

-- 

  Roger