borland

Was searching for something some tranny info and came across this on a Mercedes forum:

http://www.mercedesshop.com/shopforu...0&d=1049329382

It’s the same valve body as ours (MB 722.3). Interesting how it shows the difference between first gear starts and second gear starts. I had suspected that the difference was in the 1-2 shift valve. Maybe Steve Cattaneo can chime in?

This pdf shows the same lineup on page 10. But I also noticed the design changes to early and late 1-2 shift valve (the K2 shift valve, versions A,B,C) on page 12.

http://www.transtec.com/tech_insert/94642.pdf

Oh, and then look at the bottom of this page, where the author describes his first gear start module, a microprocessor controlled speed sensitive kick-down relay. He considered including a “GTS’s dynamic kick-down” like function.

http://juliepalooza.8m.com/sl/mercedes.htm

borland
90’ S4, Slate Metallic

Schocki

Don't forget that the kick-down function is also controlled by speed. If you're slower than 34 MPH or 55 km/h there is no kick-down.

I think I read somewhere that Porsche decided on 2nd gear because the downshift from 2nd to 1st when coming to a stop causes some unwanted engine brake like deceleration.

I don't see the need for a permanent 1st gear start. If you want 1st just floor it or shift into 2, done.

Steve 88

Borland, your post comes at a great time for me. I just noticed that while my semi-permanent kick-down (Garth's Quickie method) still works great for downshifting at speed, I seem to have lost my first-gear starts. Might be my move from Autothority chip to No-name Ebay chip. I will test this weekend.

Anyway, thanks for posting this info.

dr bob

I did an experiment with a MB place that makes one of these "modules" to get first gear starts, programmable upshift and downshift points, etc. It looks at vehicle speed and engine RPM, and energizes the kickdown solenoid to force the first gear start. Only poblem was that the kickdown solenoid on my car doesn't force a first gear start without the shift cable from the throttle helping lower the cointrol pressure. Takes both at the same time.

There may be some restriction at the shift solenoid that prevents it from dumping the control pressure low enough on its own to get the first gear start. My conclusion after all the tinkering was that I really don't need the first gear start all the time, since the 2.54 gears in my later S4 make normal starts fine for >95% of all launches. I just don't drive the car that hard in SoCal traffic, since there's no benefit except to brake, tire and gas vendors. The shift cable is tight enough to get first gear starts if I press the pedal quickly even if I never get near the kickdown switch.

Bill Ball

Will the car no longer drop into first at any time? I had that happen a year ago. A fluid change with some trans cleaner additive fixed it. I think I had a sticky 1-2 shift valve.

I have the Jager kit, not yet installed. Fussing with too many other things. Also, I'm content with shifting the AT as it it were a stick, putting it into 2 to get 1st gear starts.

However, this information is interesting. Am I reading it incorrectly? Does it literally say you will get 1st gear starts simply by taking a spring out of the valve body? Is all the other shift program experimental stuff partially intended to avoid having to open the valve body?

tv

I don't know if this discussion applies to S4's only, but my S2 always starts in 1st.

Ed MD

S2 and S3 transmissions will start in first, gas prices and a change in marketing philosophy drove the change. And I was told that the conversion is, indeed, that simple. Ed

Bill Ball

S4 through 87 also start in 1st. From the 88 MY Service Info Tech book:

Changes on Upshift and Downshift Program (Introduced in Spring of 1987)
In the past cars with an A 28 automatic transmission always moved off in 1st gear and shifted down into 1st gear with a noticable jolt shortly before stopping while rolling to a stop. A changed shift program in the valve body now makes it possible to also move off and roll to a stop in 2nd gear for certain operating conditions.

Steve 88

Bill, I can't seem to find 1st even from "2". I changed the trans fluid recently. Should I look at trans fluid cleaner additives alone? Do you recommend a brand? Thanks!

6.0-928S

Oldtimers recommended K & W Trans-X to me when I was 17. I've been using it ever since. I'm now 53. I've used it in Race Hemi Torqueflites & my 928. I'm up to 175K & my trans will still snap your neck when it shifts. My son lost reverse in his Turbo Regal. We dropped the pan & it was full of clutch material. Put in a quart of Trans-X & reverse returned for about two weeks before the clutches were completely gone. I put it in every auto trans I've had every time I do a service. Miracle stuff in my opinion.
Hammer

Bill Ball

Steve:

I just grabbed some stuff that said it helped clean varnish from inside your trans. Not the flush type, but one meant to add and drive. Initially just the fluid change got my 1st gear back overnight. Then a few weeks later it failed to drop into 1st again. I added the the trans cleaner and it came back the next morning. All good since then.

If 1st doesn't come back, then you should contact Steve Cattaneo for a rebuilt unit or further diagnostic steps.

Steve 88

Thanks Hammer and Bill B. Will look for Trans-x at local stores over the weekend and give it a try.

Barry Johnson

Sterling sold me this kit that changed some springs and what-not in the valve body, but I've since lost it (#$@%!!!). I never installed it, so I can't tell you if it works...

Sterling, do you remember where that kit came from? Might be interesting to find out what we had and what it really did

IcemanG17

My 88 will do whatever you like....anything less than 1/2 throttle...second gear....anything more BWAAAAHHHH....its fun... I did notice that when we tightened the throttle cable (to fix the WOT fault) that it takes less throttle to get a 1st gear start? I guess it also slightly tightened the bowden cable....

Bill
I've been thinking about that Jager kit too....maybe I'll get it when I get my new shift ****?

MilesOrbell

Brian, is the Jager kit anything more than a switch paralleled with the kickdown switch ?