Hey guys,

I've been chasing an issue for about 2 years now and can't find a decent answer or reason. My 1-2 and 2-3 shifts are quite harsh, kick in the pants kind of shift. 3-4 is fine 99% of the time. I've done multiple fluid changes, new filters, replaced the bowden cable and the modulator.

1-2 Shift: This is harsh at around WOT, the car starts in 2nd so I'm never down to 1 unless its heavy acceleration. I can live with this.

2-3 Shift: This is harsh at low/off throttle, basically I find this bad in parking lots. What happens is the car starts to shift, feels like its going to, pauses for a second and then slams into 3rd gear. Its not what I'd call a flare, its not slipping. It's just a pause. Under moderate throttle its absolutely fine.

Any ideas?

The harsh 1-2 shift is normal under WOT. In a programmed 2nd gear start transmission, you're on the kick down switch to force a 1st gear start and it will shift at much higher RPM.

The hesitation and rough 2-3 shift could very easily be a broken K1 accumulator spring. The part is cheap, easy to replace, and is well documented on this forum and elsewhere.

Anecdotal evidence time: My 300SDL drove like Helen Keller learning to drive stick when I got it. I found both K1 and K2 broken. Replacing them got the transmission shifting remarkably well despite it being very tired.

Haha, was just coming back to edit my post, K1 spring was replaced year and a half ago. First thing I did, but doesn't seem to have made any difference.

You may want to test governor and modulator pressure for your specific transmission part number. There is an ASTG manual floating around on the Internet that has all the testing procedures and values for the various different transmission part numbers.

How many miles on this car? If a high mileage example, you might try a bottle of the yellow Trans-X. If you have a bunch of varnish or sludge built up in the valve body it could possibly help. My SDL sat for a decade with old fluid in it. Transmission was absurdly rough when I put it back on the road, felt like it had a drag shift kit in it. Every shift was delayed and violent. Yellow bottle Trans-X helped a surprising amount. I'm not a believer in "mechanic in a bottle", but sometimes it's a band-aid that actually works.

Yeah I was thinking governor could be the cause, thought I had it figured out when I couldn't get it to upshift, figured the gear had broken but turned out to be an overadjustred bowden. I'll try and track down the test procedure.

The shop that adjusted the modulator did multiple adjustments to it, I was adamant they got it right so I don't think theres an issue there.

I know this is a really old thread, but I'm wondering if you ever got to the bottom of the cause?
I've got exactly the same issue with my 2nd to 3rd shift. Under very light throttle it kind of delays shifting, then bangs into 3rd. Worst in car parks, or when pulling away in traffic when the car in front goes slowly, so I have to lift off while pulling away gently. Even with just moderate load it's super-smooth. 3rd to 4th is always smooth.

This is a K2 problem. Replace the spring and if that doesn't work, try replacing the piston itself.

1) AJB understands that the trans is a four speed. (It is sometimes mistaken for a three speed.)
2) The 2-3 shift involves the release of band B1 and the application of clutch K1. Hence the accumulator and spring for clutch K1 is the likely culprit.
[Accumulator K2 is involved in the 3-4 shift.]