Simon928

I have a 1990 S4 and on at least two occasions over the last few days the transmission seemed to get stuck in kick down mode where the transmission wouldn't shift until red line. I never put the pedal to the floor or anything close to that so I'm not sure what caused the car to enter this mode, but the only way I could seem to get out of that mode was to temporarily shift into neutral and then back into drive.

Does anyone have ideas as to what could cause this type of failure? Could this be caused by a failing kick down relay, a failing kick down switch, an improperly aligned cable or a problem in the transmission itself? Any input would be greatly appreciated.

AirtekHVAC

chart928s4

Had a similar problem on my car - check the cable and jacket to be sure they are still in good shape. My kickdown cable jacket was effectively lengthened by an inch or so due to the jacket splitting. The cable acts like a bike brake cable, i.e. it pulls against the jacket and mount points to create tension. If the jacket lengthens the tension is higher.

The cure was shrink wrapping it while pushing the jacket halves together so the intact ends were as close as possible. After the cable was stabilized it was still too tight, so loosening the cable at the throttle quadrant was needed to get smooth shifts. Worf928 diagnosed it and did most of the fix. He may have more comments/advice.

There are other possible causes, but the above is worth a look.

Good luck!

FredR

I have a kick down bypass switch that I run more or less permanently engaged [by choice] and my transmission behaves more or less normally so I doubt the kick down switch is the issue. If it were a sticking throttle cable then similarly the problem would not reset when putting the transmission into neutral as the engine would race.

As to what is causing your issue I do not know - were you engaging cruise control at the time by any chance?

Landseer

Possible broken return spring. Found that on my 86 recently. Drop the pan to inspect.

Simon928

Thanks for the input everyone! I never considered that the sleeve splitting could be a possible failure point, so I'll inspect that when I get a chance. Am I assuming correctly that you are referring to the section of cable in the engine bay that connects to the throttle plate?

And Chris, thanks for the suggestion about looking at the return spring in the transmission. I had the pan off over the winter and I would prefer not to have to go back there again, but if my other diagnoses don't prove fruitful I will take a look in there. If I do I might be asking you which spring I should be looking at, although if it was broken it would probably be in the pan. In your opinion would a broken spring only be causing intermittent shifting issues like I am experiencing?

After thinking about this overnight the more I am leaning towards this being a cable issue, possibly just due to some misadjustment. Last year I had the throttle plate off and when I put it back on I noticed that the throttle cable was a little too tight (you couldn't hear the "click" on the idle switch on a light press of the throttle) so I had to loosen it a bit. I noticed this year while driving the car that sometimes when I was driving and I took my foot off the throttle and was coasting to a stop my transmission would shift at a different point then normal. It never really bothered me too much so I just filed it in the back of my mind for the next time I was poking around in the engine bay. Now I'm wondering if all of this is related and I just have an issue with my throttle and/or bowden cable being misadjusted. I have seen some posts about the proper adjustment procedure for these cables so I will try to start this procedure fresh and make sure that everything is adjusted properly. I figure that is a good first step, and if that doesn't change anything I will move along to other areas.

Thanks again for the suggestions!

chart928s4

Yes, the split happened about a foot from the throttle quadrant in the abyss behind the engine but above the hard sleeve on the bell housing. We didn't notice the problem until after a new throttle cable installation (+ tons of other work).

Also, rumor has it that if you have changed one cable, they will all need to be tweaked. So that could certainly be the issue all by itself. There is quite a bit of thread to adjust on the ball end of the kickdown, so you can loosen a little, try it, and repeat until you either get it fixed or run out of threads. My car shifts silky smooth now. And it's among the easiest adjustments to do/undo - just don't lose that stupid tiny retaining clip!