A/T Issue on my '89 S4
 

When I take off from a stop the A/T wants to immediately downshift to 1st gear unless I very lightly feather the throttle. I believe these cars were designed to start in 2nd gear? Is it possible I need to adjust a cable? It was like this when I bought the car, so maybe a PO messed with the adjustments? It's not that I don't like starting in 1st gear sometimes, but I can manually do that with the shifter. For regular city driving having it downshift to 1st is a PITA!

Thanks,

Glenn

Is your car a US or Rest of World version?

Also, is there a possibility that the kick-down switch has been shorted out?

to test the switch first simply turn the key to the run position, listening for a click at the rear of the trans.
Then if no click then mash the pedal to the floor see if you hear it.
If nothing then check the fuses. there is also a connector that you could unplug next to the kick down switch under the gas pedal, possiblyt the PO has wired the switch to be always closed and you have not found the second switch to switch it off.
Also check the tension on the transmission bowden cable , the ball cup should fit over the ball without the cable being loose or tight

That sounds like the bowden cable is too tight. Easy to adjust it.

Could be the cable is a bit tight, mine is like that on purpose so that it starts in 1st, however that is not as you describe where it changes down to 1st from pulling away so I would check for kickdown enabled all the time. How does it behave in other gears, do you have to feather it too?

It is an ROW car. It seems like the kick-down switch is working okay but I will double check it. All other gears seem fine and shift properly, although the upshift from first to second is a bit harsh under part throttle, smooth under full throttle. As I mentioned, it stays in second as long as I don't as much as breath on the pedal, but as soon as I put any pressure on the throttle it drops to 1st. I will also check the cable. Thanks!

I think my car shifts from 1st to 2nd quite hard under gentle throttle and under full throttle or near it is still quite hard but you probably don't notice it as hard because if it was soft I think you would get slip in the gearbox, and as the rest of the gears are working ok that tells me the vacuum operation is fine. In fact mine will light up the rears on changing 1st to 2nd under hard acceleration.
You say the kick down is good so if you are doing 50mph in drive 4th and you mash the pedal, it changes to 3rd and if you engage the kickdown it drops to 2nd?
If so it certainly sounds like the cable.

Hmmm...good question. It certainly does drop from 4th to 3rd when I mash the throttle, but I can't recall it going from 3rd to 2nd when I hit the kickdown switch. I didn't realize it was suppose to drop two gears once the kickdown switch is enabled. I will have to try that...maybe the problem is with the kickdown after all.

I have found that if the kickdown is bypassed that if you start with the shifter in 2 then go and upshift to 3rd and let the tranny upshift to 3rd, then move the lever back into second, it finds a false nuetral and doesnt grab anything until you bring the engines RPMs up to match the speed you are doing. This only happens when the kickdown is bypassed.

I am guessing this means you got your car back on the road?

I have to check the manual for that exact diagnostic, but it could also be your modulating pressure. Here are some pics of a kit my friend put together to service MB 722.XXX transmissions. Getting your pressures checked and adjusted properly can make your tranny shift so much smoother. I used this set-up after a R and R on a MB AT 722.424/W202 chassis.

In the kit (HFT base) below, notice the banjo bolt (acquired from a MB junk yard, to hook it up to the pressure fitting. I can send it to you, but I must have it back as it is not mine. Michael

Hey Colin, no, not running yet...that sensor I need is not available locally.

Michael, thanks for the generous offer! I am going to do a few more checks and I just might get in touch with you to borrow the tooling.

Glenn

No problem. My pleasure. I will send it on your say so.

Harsh shifting is directly affected by mod pressure abnormalities. Delayed shifting is usually a component of bowden cable adjustment or other.

Also, PM me or post email if you want me to send you copies of any useful documentation ;).

Well, turns out it was the bowden cable...re-adjusted it to the proper spec and all is good! Looks like a PO adjusted it to start in 1st and over time with some wear/stretch it was right on the edge between 1st & 2nd at the idle position.

As a bonus from the info I recieved here, I checked out the kickdown circuit and found it was wired properly but the throttle assembly was not contacting the switch. A quick adjust took care of this and now everything works like factory!

Thanks all for the help!

Glenn