79 300D upshifting problem - PeachParts Mercedes-Benz Forum

subiracer06 · #1 08-31-2011, 12:06 PM

hey guys,

new to this forum, but have done a lot of reasearch and came up empty.
i just bought a 300D that has a 722.118 trans acording to the stamped ID. this trans has no vacuum control so how can i adjust the shift points.

my problem is that i have to rev the engine out then let off the accelorator to allow the trans to up shift. it goes through all gears fine it is just the up shift it will no do uless you rev it really high.

is this trans adjustable by the linkage connecting throttle to the trans?
what fluid and how much to put in if i decide to replace?

there are no flaring issues, although i should add, if i get back on the pedal too early it does shift hard. if i allow time for the trans to shift, it shift smoothly. i have ordered new trans filter so i will check levels and see if filter is clogged first. is it worth it to adjust the linkages?

any advice is much apreciated

thanks,

Jimmy

subiracer06 · #2 08-31-2011, 12:09 PM

also to add to the picture, there are no vacuum lines going to the trans. on top of the valve cover there are no cam action vacuum assy. there is no VCV attatched to the rear of the fuel system.

thanks again in advance

- Jimmy

Dieselboy740 · #3 08-31-2011, 12:31 PM

The 722.1 uses a mechanical arm as a kickdown is yours still there.

kerry · #4 08-31-2011, 12:34 PM

Quote:

Originally Posted by Dieselboy740

The 722.1 uses a mechanical arm as a kickdown is yours still there.

No electrical kickdown switch? I was going to suggest unplugging the electrical switch and seeing what happens.

Dieselboy740 · #5 08-31-2011, 01:17 PM

It still has the kick down button under the throttle pedal. Your up shifts are controlled by the lever though.

kerry · #6 08-31-2011, 01:26 PM

Then unplug the kickdown switch. It could be stuck on. If it is, it causes high rpm shifts.

Dieselboy740 · #7 08-31-2011, 01:33 PM

If it stuck down it won't shift till after 4k and when slowing down it will downshift on you.

subiracer06 · #8 08-31-2011, 01:33 PM

i believe the kick down switch is still working because i can feel it when i fut the throttle the extra amount down and feel it click. i will try the disconnect it tonight and see if anything changes.

the linkage is still connected, should i try removing it from the upper assy and lengthen or shorten the assy?

-Jimmy

subiracer06 · #9 08-31-2011, 01:36 PM

im not sure the RPMs bc mine did not come with a tac, but it does infact down shift when i let off. doesnt it do this automatically as you come to a stop? i would imagine the kickdown swith being stuck would cause this to happen at a higher RPM right?

it looks like were leaning toward the kick down switch. that will be the first thing i check.

thanks again for the input guys

- Jimmy

Dieselboy740 · #10 08-31-2011, 01:37 PM

Try in unhooking it at the valve cover and see if it shifts right away in every gear.

subiracer06 · #11 08-31-2011, 01:44 PM

that will be #2 on the list.

thanks

-Jimmy

Stretch · #12 08-31-2011, 03:58 PM

Quote:

Originally Posted by Dieselboy740

The 722.1 uses a mechanical arm as a kickdown is yours still there.

Eh?

Are you by any chance talking about the lever that you can see on the transmission in the front in this picture?

Dieselboy740 · #13 08-31-2011, 04:09 PM

It's not a kick down but a throttle position lever. It tells the transmission where your foot is to modulate up shifts. The vaccum controls firmness.

Im not exactly sure and I could be wrong but that's what was effected on my trans when I messed with it.

vstech · #14 08-31-2011, 04:34 PM

the rod is a bowden ROD instead of the bowden CABLE we are used to with the more modern trannies.

adjust it as you would the cable. I think it's tighter for sooner shifting looser for later, but either way, adjusting it should make a difference.

the .1 should have vacuum attached to it, but it, like the .3 trans is for firmness, not really for timing of the shifts...

Dieselboy740 · #15 08-31-2011, 05:29 PM

On my car I run the vaccum unhooked because I want firm shifts all the time no matter throttle position. I also turned the pressure up to the point I blew the first transmission case in half. I learned the hard way.