280SL Auto - how smooth (or not) are the Auto transmissions? Hard shift 1-2

[jf308]

69 280 SL

1st to 2nd shift comes with a bit of a jolt/clunk... then relatively smooth for the other shifts.

Prior owner states that this is pretty normal for all Automatics.  What has you experience been? 

(note: the rubber mount in the center of the trunk moves a bit when engaging R or 4 coming out of Park.  I plan to replace that bit, but don't think its related to hard shift 1 to 2).

Thanks.... John

[Cees Klumper]

Mine shifts smooth through the gears, up or down.

[BaronYoungman]

If I get on mine that first shift is hard and get some wheel squeal... If just cruising from the light not as noticeable.  May need to be adjusted if yours shifts hard under even slower acceleration.

[jf308]

are these fairly easy to adjust?

[thelews]

When I decided to get a Pagoda, I insisted it be a stick.  

I remembered my mother's 71 (bought in '72) with automatic and said no way.  Set up to start acceleration in 2nd gear bothered me, and the shift to 3rd was a jerk.  1st gear was for pulling stumps and if you didn't use the gearshift lever to select 1st, you had to hit the kickdown switch by flooring the car. Downshifts by pressing on the gas without the gearshift as I recall were reluctant and required hitting the kickdown switch.
  
I do understand today that good Pagoda transmission guys can make adjustments to smooth out shifts.  Also, using the gearshift and modulating the accelerator pedal to coordinate shifts can be fun.  But, all on its own, the automatic transmission left me wanting.

[Rolf-Dieter ✝︎]

Hi John,

Mine shifts just as you describe (first and second a bit rough) I manage to smoothen this out by letting off on the accelerator and then giving gas again once it shift is completed. This helps smoothen it out. It will have to do until such time that I find a capable and experienced mechanic to do some adjustments (I too have a 1969 280 SL Automatic).

I do know there is a problem with the knockdown switch [getting no power when checked with the volt meter] a capable Pagoda mechanic has checked and verified this, however, he was not able to correct the issue, perhaps a new switch or wiring is in order.

[ja17]

These early 16 bolt (oil pan) transmissions  typically have a firm shift compared to modern transmissions. The shifts should felt but should not be severe or jerky going up or down with normal pedal. As more accelerator is applied the shift will become later and more firm. Activating the "kick down" or downshifting to lower gears will create more abrupt shifts. These  transmission are mostly smooth and comfortable to drive when adjusted properly.

You can review the section  27 of the BBB to find exactly how and when the transmission should shift, up or down, at different speeds and settings. Be sure you view the specs for the KA4 025 transmission since other units are covered in the BBB also. This style transmission is most easily recognizable from their "16 bolt oil pans".  Later units in other models had 4 bolt or 6 bolt oil pans.

First of all it is most important to make sure that the three position solenoid on top of the transmission is working correctly. This solenoid or its linkages and pivots can get corroded and stuck from lack of use. You can check and view the linkages from the access opening in the transmission tunnel. Look on pages 27-23/3 thru 27-23/5 for information on the solenoid, venture switch and linkages.

Adjusting the modulator pressure should be carried out only after all the linkages, switches and the solenoid has be checked. It is a little more involved since a special fitting is required to tap into the test port. A basic pressure gauge is also required. Page 27-0/3 of the later BB list the modulator settings. Page 27-23/14 describes "Measuring of Kickdown Modulating Pressure". Page 27-25/5 of the late BBB describes more on "Measuring" the modulator pressure. If you do not have access to the BBB, check the Tech Manual on this site and ask more questions as needed.

Sometimes it is most helpful to drive in a Pagoda which is shifting correctly so you can realize what it should feel like.

[Rolf-Dieter ✝︎]

Thanks Joe for a great reply as always!

Marry Christmass to you and the Family
and a
Healthy and Happy New Year!

[jf308]

what is the BBB? and as a full member do I have access to it?

I am aware of the Technical Manual but have not seen BBB referenced before.

[Cees Klumper]

BBB is short for Big Blue Book, which is another name for the hefty MB Shop Manual. David Pease coined this term some ten years or so ago ...
We don't have it on the site, you can find old copies on Ebay and I believe it was/may still be available from MB in digital form.

[66andBlue]

what is the BBB? ....

Also don't forget to look at this page in our technical manual. It shows the BBB versions and also other useful books:
http://www.sl113.org/wiki/Documents/BBB

[ja17]

If you do not have a BBB, Sun Valley Auto Dismantlers in California, have a good adjustment procedure on their website for the automatic tranmission.

[jf308]

Thanks Joe.  

Will access that now.  I am sure that its an adjustment of some sort....transmission had been rebuilt professionally (prior owner).  I am guessing that it just needs to be dialed in to alleviate a bit of a hard shift.

That procedural method looks good.

Regards, John

[J. Huber]

Just another experience: mine is pretty severe 1-2 but this is rarely a gear I use. If I start with shifter in 2, and from a dead stop, really ease the pedal, I can make the shift a little better. But normal acceleration in 2 (1 to 2) makes the car practically leap. A firm pedal gets tire squeal and neck ache. I take off mainly in 4, but sometimes 3 depending on the lay of the land. Favorite way is firm acceleration in 3 (which drops me to 2), then the shift to 3. I then shift to 4. These shifts are pretty smooth (not seamless like modern cars but often almost.)

[ja17]

John, pay special attention to the correct adjustment of the electrical switch on the venture. It is the most common cause of hard shifting. The next most common cause is stuck solenoid linkages on the automatic transmission.

[Paul Heath]

I know this is an old topic, but could you clarify what the "Venture" is or was that a typo?

Many thanks
Paul.

[mbzse]

Picture showing the device, on inlet manifold

[Jonny B]

Yes, that is a typo, it is "venturi" not "venture"

[ja17]

Thanks Jon!

[Paul Heath]

Thanks for the clarification gents. How is it adjusted, any special tools required?
Thanks
Paul

[Mike K]

To add to the input above, another contributing factor which I found improved the shift changes, especially from #2 to #3, on my 1971 280SL Auto, was replacing the  transmission mount, filter and fluid.

See my old post: https://www.sl113.org/forums/index.php?topic=25341.msg181334#msg181334

Two things I found after doing this job:
1. Automatic gear changes became unbelievably smooth and barely noticeable, whereas before I felt a moderate kick in the backside with each change.

2. When coming to the top of a steep incline there was an issue when moving the shift lever from #2 to #3.  There would be a delay of about 10 seconds before the gear engaged, and when it did engage there was a hard clunky kick in it.
This symptom immediately went away once I replaced the xmission mount, filter and fluid.

Best,
Mike

[Pawel66]

1. Automatic gear changes became unbelievably smooth and barely noticeable, whereas before I felt a moderate kick in the backside with each change.

I wanted to add to the benchmark - indeed it is maybe not difficult to notice gear changes, but when do not specifically py attention - you will miss it. It is really a smooth shift. You hear engine tone change, feel car accelerates differently, but no kick of any kind.

[Paul & Dolly]

The "Venturi" rotary switch can aslo become defective, as in my post of August 2016, here

https://www.sl113.org/forums/index.php?topic=24794.msg177342#msg177342

I have had no further problems since then with it.

Paul