Run, don't walk, to the dealer, get a K1 kit!!!
 

Installed this tonight in my beloved "semi-automatic" (gotta lift to shift 2-3, or she will roar- has always been thus) 1981 300SD.

Best $12 I have ever spent.

Oh, so smooth. It shifts like a new car now. No flare, ever, no jerking, roughness, it's glorious.

I have never gotten this car to shift without lifting throttle @ 25 mph before. Been driving it for almost a year. Fluid looked great, BTW, and it was at least 20K miles since last change.

If your 123/126 shifts any worse than your neighbor's W210 etc., GO GET THIS PART!

Thank you, and goodnight!

got a part number and for what models, please?

That's good info.

Many members have the dreaded 2-3 flare and struggle to fix it with vacuum changes under the hood.

I suffered with the flare on the W123 for several years.........driving it just like you did. The slightest upgrade required a lift of the right foot........or it would flare.

PN# 126 270 44 77

I ordered this based on recommendations of this forum. I believe it fits all 722 AT transmissions.

My opinion: If you have fiddled with vacuum trying to stop flare, set it back to stock settings. Then install this, and leave that modulator ALONE! I adjusted absoultely nothing in my time of ownership, except the position of my right foot at every 2-3 shift. I left all settings alone, installed the kit, perfect shifts immediately.

You'll find yourself looking for an excuse to drive the thing when you're done!

Does this fit on an 80 300SD? I also have the foot-lift problem from 2-3.

here is the fastlane kit

http://catalog.peachparts.com/item.wws?qty=1&mfr=MBZ&sku=1262704477&price=15.00&cookieID=1Q51D2K1C1Q81CID6Y

how long does it take to install, and or how hard is it to install?

Picture please... What is a K1 kit?

This part adds 10-15 minutes to the time needed to do a trans fluid service.

It's in the valve body of the transmission. I didn't take any pics, sorry. Do a searce on K1, spring, kit, and you'll find that this topic has already been discussed many times. I'm just saying that it is definitely worth your time and effort to install if you have any flare issues at all!!

How long has this been available? My 300D trans was rebuilt by Peter Schmid
in Mt. View Calif in 1997. (they now moved) It shifts real smooth through all gears.

I wonder if they used this module. I know that he would improve on the original design with his rebuilds.

Thanks Peter Schmid

uhm, for the Dutch people here,
 

Who don't understand English 100 percent::)

What do you mean by `flare´ ???
That the tranny slips a second when its in the next gear??

I have a small problem with my tranny in my w123 300TDT: It shifts from 1st to 2nd with a bit of a shock. Can this also be changed by this K1 kit?

K-1 kit is for the 2-3 shift. Check mbz.org, I think they have the instructions on this under articles. I just did mine last weekend, big improvement.

Just checked mbz.org and their article about the K-1 is not there. Do a search for it to find the location. After you get the cover off it just pulls out, easy job.

Yep, that's it. Sometimes it slips for more than one second and the rpm's run away between shifts.:eek: That's why everyone backs off the pedal to force the 2-3 shift when they have problems.

The 1-2 shift on the earlier W123's is typically harsh. It was corrected in the later vehicles. I don't think you can easily correct this on the earlier vehicles without some decent expense in changing components within the trans.

It is possible to increase vacuum to the modulator to soften all shifts. However, if you have any 2-3 flare, this would make the flare much worse. If the 2-3 is sufficiently firm, then increasing the vacuum from the VCV (if adjustable) will soften all shifts.

Condensed instructions: http://www.peachparts.com/shopforum/diesel-discussion/141392-i-broke-k1-repair-kit-what-did-i-do-wrong.html

Reply #5


I believe there's a band that will fix the 1-2 shift. Haven't really looked into it because I haven't needed to.

Thanks for the info, but I'll leave it alone. Dont fix it if it aint broke.....

Dont wanna worsen the 2-3 shift.

Does the K1 also affect the 3-4 shift in an 81 300sd?