Ninespub

I've read here sometime ago that there was not much difference between the 4 spd auto trans from MY to MY but that the last GTS's did have some differences in the kickdown (or something) that made it a little better. What was it that did that, and can you update a '91 MY to take advantage of that enhancement? I noticed that 89-91My uses A28-16 as a designation and 92+MY uses a G28-18. Are they all still the Mercedes 722.3 tranny?

Paul Barrera
'91 $4 (undergoing refurbishment)
'03 BMW 325ci Coupe 5sp
'07 Mini Cooper S (coming)
'01 Audi TT Quattro 6sp (going)

Bill Ball

Dynamic kickdown...here's a good thread...
https://rennlist.com/forums/showthre...namic+kickdown

Cliff Ruckstuhl

Does dropping the shifter down a gear do the same thing?

Cliff 87 S4 Murf # 44

borland

No. The transmission will kickdown into a lower gear just by sensing throttle pedal's the rate of change. So the downshift happens much faster than by moving the shift lever to a lower gear or by floor boarding the gas pedal to activate the throttle kickdown switch.

The full throttle kickdown switch programming is also available with the GTS dynamic kickdown mod.

Dynamic kickdown function is limited to the program within the GTS dynamic kickdown relay. In the above link, Schocki has posted Porsche's description of the program's functional parameters.

Cliff Ruckstuhl

I understand it will do it much faster and it will do it just by pedal postion. But is it just dropping a gear like moving the shifter but doing it faster?

Cliff 87 S4 Murf # 44

Ninespub

Bill, thanks for the link. Borland, thanks for the short "splaining" and Wolf Pack thanks for asking questions that I didnt yet! But I'm still wondering if my tranny is the mercedes 722.3. There is a shift update kit that could help resolve any 2-3 gear flare (which I have, IIRC) that applies to the above transmission model and i was going to install it (if its the correct trans for the 91MY) and I figured while I was in there........! It looks like the dynamic kickdown mod will have to wait until I rip the intake off some other day (and $$$) in my life.
Paul Barrera

borland

It doesn't do anything other than activate the electrically controlled kickdown solenoid valve at the transmission.

Only thing different from the earlier GTS/S4 cars, is the throttle sensor and the kickdown relay programming.

Has nothing to do with the shifter position. There is no shifter position feedback in the circuit.

Kickdown solenoid activation is not the only control that causes the transmission to shift down. Downshifting is also controlled by the transmission's valve body programming with inputs from gear selector lever, throttle position (by the bowden cable tension), and from the speed governor.

borland

All 928 4 speeds are Porsche versions of the Mercedes 722.350. Same as used on the MB 560 SEL and most of the parts are interchangeable. Porsche uses mercedes part numbers in the PET parts database when applicable, so you can source the parts using the PET and go to a Mercedes dealer parts department to get them, usually at lower cost.

Cliff Ruckstuhl

Paul,

Are you having a problem with the 2-3 shifting flare? Where it will rev just before it shifts into 3rd???

Cliff

Ninespub

Hi Cliff. My '91 $4 has been "in storage" for over 3 years and so I cant remember the rpms. Next week I am: changing all fluids, filters, belts, hoses, fuel & brake lines, tie rods, front wheel bearings, rotors & pads, shocks, a bunch of relays, battery, thermostat, plugs, caps and etc. The parts are in!The last time I drove it, it was sluggish and shifted like an old buick on the 2-3 upshift and I know that I wasn't low or had bad trans fluid. I had read on rennlist about the updated shift spring kit that MB had brought out for what became a "common" issue for our auto trans. I understand it like a $25-$30 part that can be put while changing the trans filter. Thats all I know at this time.

Paul Barrera

Cliff Ruckstuhl

Paul,

There is a spring switch in there that causes a 2-3 high rev shift. I had mine done last winter. I am not sure what the part number is. If your doing the tranny filter and fluid it is right there. Do a post on it reving between shifts and some one will jump in and know where the post is.

Cliff 87 S 4 Muef # 44