Does anyone speak "Automatic Transmission" (1969 Mercedes variety)

1969 Mercedes 200 Automatic (W115) 4-speed variety, starts in second I believe, and shifts from there. Only uses first for hard acceleration.

Car shifts to and through Park, Neutral, and Drive but will not shift gears through drive. No slippage, no nothing. Just runs up the speed, then drags back down the speed when you let off. It revs and drags like a manual would if you accelerated and decelerated and didn't use the clutch, but idles just fine while stopped in drive.

I've tried checking the hose to the vacuum modulator for leaks by sucking it and plugging it with my tongue. No leaks detected (sorry, I'm working with limited resources here)

The old fluid from the trans looks like this:

I had the pan off and checked the torque of the bolts holding the valve body on, and they were tight-ish but I have them at 8ft lbs or so right now.

I replaced the filter while I was in there and topped it back up with Dextron III (type H)

The button under the gas pedal checks good for operation with my multimeter (open when it should read open, closes when it should read closed)

I would like to look at the vacuum modulator adjustment, or the governor next but have no idea HOW to adjust a vacuum modulator, or where the governor is on this car. Google hasn't been much help at all, and I have found surprisingly little info on this cars trans online or in my manual.

I think this might be where the governor resides but cant get the cap off to save my life

and I'm calling this the vacuum modulator:

This is my first time ever tinkering with an automatic transmission so please bear with me while I ask you tons of stupid questions. Before the start of this day, I knew autos had planetary gears, and their fluid was red. That's it. Not exaggerating

Thanks guys

The vacuum modulator isn't adjustable (unless its some mercedes voodoo that I don't know about). There is also not a likely cause for it to suddenly become un-adjusted, therefore I would surmise that its either good or it isn't. Usually they just get fail and you replace them.

Same with the governor. There is no reason for it to change. It either governs or it doesn't.

Valve body could be an issue. They can develop cracks which leak hydraulic pressure, the check balls can wear out, pistons can seize in their bores, and you can get wear in the separator plate (gasket) that allows check balls to get stuck or go through altogether.

You mean to say the D position is behaving like 2? Does it use a throttle valve cable? Check the vacuum lines more carefully, trace all the way from the modulator to the intake manifold. I think these are a little more complicated than a simple line directly to manifold vacuum and you were in there messing with the carb recently.

EDIT: Also, at which point did you test the kick down switch, at the switch, or at the solenoid? If you have a wiring fault that could do it depending on how it's wired. Kickdown switch was this guy's problem.

I'll ask my friend that plays with 80s Mercedes stuff (same trans) next time I see him, he had one of those transmissions a long time before he figured out how to put a manual in everything.

A little more background? Did you buy it this way? Did it suddenly start happening or was it a gradual problem? Did something happen (fluid change, filter change, fender bender, etc) that marks the start of the problem?

Yugo:

Right. D behaves like 2, but that's normal for this car. It'll only shift down to 1 if you're really getting on it from low speed. I tried forcing it to downshift by romping on it, and by shifting into L and neither had an effect. I'll go look for a cable near my throttle assembly, but I'm thinking it doesnt.

Curtis:

Interesting on the modulator. Sorry for my confusion, I've been trying to get my info from other planetary transmissions (in this case the TH350) Here's the thread I referenced:

https://www.jalopyjournal.com/forum/threads/turbo-350-trans-wont-upshift-from-first-gear.470242/

How can I troubleshoot between valve body, Governor, and Vacuum modulator?

I've found a repair kit on this site about 1/3 way down on the right column, but it doesn't give any info as to the contents (balls, gaskets, etc). Any thoughts: http://www.type300.com/w114---w115.html

A search for "Mercedes W115 shift kit", yielded zero results.

Also is it normal for these to fail overnight? I drove it home around 5pm last night and it was running like it usually does.

See edit, also for looking for info/parts I think you have a "722.0" trans, being a Mercedes that will probably be stamped on it somewhere.

IIRC you'll know if you have a bad vacuum modulator, you'll get a lot of oil smoke from the exhaust since the engine will suck ATF out of the trans.

BrokenYugo wrote: See edit, also for looking for info/parts I think you have a "722.0" trans, being a Mercedes that will probably be stamped on it somewhere.

Saw that same video! Yeah, that's why I went there. So I tested the switch at the switch (behind the gas pedal). 12v on one wire going in, nothing on the other. The switch reads open when it's not being pressed and closed when it is. The wires going in to the switch dont read any continuity between each other (so they're not shorted together). Is there a way I can disable the switch at the transmission?

Also, regarding your question about the cable. There is a linkage going from the throttle linkage back to the transmission. It looks like it pulls something just aft of the bell housing.

Ok, no oil smoke out of the trans so that's good news!

(also no ATF in mouth when I was sucking on it either. You know... for extra verification and all. You can't be too sure about these things you know...)

I haven't seen the transmission part number yet (it's getting dark out already, and the car is off jacks) but here's a shot of the valve body part number if that might help any (sorry it's blurry, it's also very humid out)

You might want to check the book on how that linkage should be adjusted, though I doubt that would cause it to suddenly misbehave unless something came apart.

On the kickdown switch I suppose the question is if it's switched power or switched ground, I don't know Mercedes wiring practices. If it's switched ground (solenoid is always hot) the wire could short to ground somewhere and give you trouble. I would assume there's a connector on the trans you can pop apart to eliminate this.

Usually if a modulator fails it's going to give high rpm upshifts because the modulator is a spring pushing a valve into the trans and vacuum pressure works against the spring and weakens it. So without vacuum, or with a torn vacuum diagphragm (which you'd know because you'd be sucking ATF into the intake manifold with engine vacuum then) it just reverts to what it would do at WOT, which is high rpm shifts. A lot of people won't rev the car high enough to figure this out, though.

I seriously doubt it is modulator related at all because that has no effect on engaging 1st gear through the kickdown switch etc.

curtis73 wrote: A little more background? Did you buy it this way? Did it suddenly start happening or was it a gradual problem? Did something happen (fluid change, filter change, fender bender, etc) that marks the start of the problem?

Krikey, I missed this. Sorry Curtis:

Background. Nope, car ran fine yesterday. I usually lift the throttle a little to let the car shift, but otherwise it's smooth.

I did adjust the shifter to transmission linkage. I found a missing bushing so I tightened the linkage a little to try to minimize the amount of overtravel I had to do when shifting from say, D to R (I'd have to overtravel R a little to account for the bushing space). I've since put that linkage right back where I found it.

The tailshaft leaks a little. When this problem manifested itself, I immediately checked the fluid level. It measured on the dipstick right below the cold line. Less than half a quart of fluid brought it back up.

The intake tract pre-carburetor leaked like a boat. It's sealed up solid now (last leak plugged before car was started this morning) but I have no idea if that's had any affect on the vacuum levels.

Vigo: Ok, so modulator is definitely out of the question. That leaves governor and valve body.

Yugo: My book sucks. I mean it really sucks, and it was the only one I could find. I'll see if I cant find an adjustment procedure out there though. I think I remember reading something today like "pull it until you JUST feel friction and tighten it down there", but I'll double check. I'll also see what I can do about disconnecting the wires at the trans. I did try driving with the switch in the cabin unplugged, but no change.

Thanks everyone!

With the GM TV linkages I've messed with you generally set them to be more or less bottomed out when the throttle is wide open, those have a nifty ratchet adjuster to make it easy. The looser it is from there the less line pressure you'll have (so it won't shift firmly enough, or maybe at all if it's really loose).

Yugo: Well, I can give it a look So you're saying, foot to the floor that lever should be as far as it can travel in that direction?

Here's the only semi-relevant blurb my book had on adjusting the transmission (the only other blurb was how to adjust the shifter. Posted above)

But this involved engaging the transmission when we come off idle, right? So not anything we should be looking at.

(not kidding either. The rest of the "gearbox" section is just how to remove and replace it. And even that's not that great)

Check the bowden cable and see if needs adjusted.

Slippery wrote: Check the bowden cable and see if needs adjusted.

(I had to look that up)

I think on this one it's a rod that connects the throttle to the transmission (or at least I think that's what I thought I saw). Yugo said in his experience it was full throttle and armature adjusted all the way in that direction. I haven't found the adjustment procedures for this transmission yet.

in this link: http://www.type300.com/w114---w115.html

2/3 of the way down in the right column is a small white valve titled "transmission modulator". This is the vacuum modulator we're calling good because we're not sucking ATF, right?

I sent an e-mail to the guy who runs the website (because he didn't have a shopping cart and his website looks like it was last updated circa Y2K). If he responds, I'll have the valve body repair kit on order along with a few other bits and bobs.

Thanks again everyone!

We're calling the vacuum modulator itself good, but I'd make sure there isn't any funny stuff on it's circuit, make sure the hoses/lines actually flow and aren't kinked or collapsed internally somewhere, maybe just replace the whole run on general principle.

EDIT: Going back though your main thread I will say that does look like a healthy trans, so this is probably something stupid.

BrokenYugo wrote: We're calling the vacuum modulator itself good, but I'd make sure there isn't any funny stuff on it's circuit, make sure the hoses/lines actually flow and aren't kinked or collapsed internally somewhere, maybe just replace the whole run on general principle. EDIT: Going back though your main thread I will say that does look like a healthy trans, so this is probably something stupid.

For the unindoctrinated, the transmission starts about half way down: https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/1969-mercedes-200-because-they-said-it-couldnt-be-/128864/page9/

the owner of the website replied to my order request (I know, I'm as shocked as you are!!!) so I do have a "valve body repair kit" on order.

Aside from the intake tract repair (post carburetor), and the adjustment I did to the trans (which I immediately undid) I really cant thinkg of anything else I touched... This is a head scratcher or sure...

raises hand

I have a question.

Weren't Mercedes known for wanting to be so ultra smooth that they always started in 2nd unless at WOT?

In reply to Knurled:

Yes, it's been mentioned in here that this trans does that. But it sounds like the problem is that it's only using 2nd gear and not any of the others at all.

full resolution diagram

It looks like the governor would be item 680, which looks like it is outside the main case and inside the tailhousing. The big flat slot thing you posted earlier is apparently a secondary pump housing. And you're right.. it is difficult to find much good information online about it!!

aw crap... That scares me to death, but you are my hero for finding it!

Up at 3:50am. I was thinking that since I've been plugging air leaks that maybe i was drawing more vacuum and that was having an effect on things. Unhooked the ducting from the carb and went for a drive. No dice.

I unhooked our vac line at the trans and drew a vacuum. It's not plugged. But i noticed the head of that modulator spuns freely (normal, i think)

Drew a vacuum at the manifold side again just to be sure and it still holds air tight.

The sun is coming up, I think I can see well enough to try that throttle armature do-dad adjustment now.

Update in picture form (computer wasn't connecting to the internet during the last post:

(that was just to try to capture the spinny head thing. I'm sure that's normal for this unit)

Next up is foot to the floor and adjust the lever on the trans. And I dont care what the damn movies say, that's way harder than it looks. No amount of bricks in any arrangement would hold that down (or break it's stride, oh no. It had to keep on movin...)

Lucky for me I snagged a broken piece of nylon tube recently

From there I crawled back underneath the car and saw the lever, but didn't see any way of adjusting the linkage (other than changing its position on the spline). I looked underneath the hood again and saw the adjustment point I was looking for (in an awful awful location) and I immediately noticed that it was almost at the end of its adjustment in the "tighter" direction.

If my shifter adjusting is any indication, that means there's a missing pushing (see? I can learn things!)

That zip tie was the best I could possibly do to try to fill that gap(no really, the access is terrible!). I really didn't expect much to happen but...

(you know what I'm going to say, don't you?)

IT WORKED!!!! I got a shift out of it. It was just once, but we got it to shift!!!!

Ok, now, I need to think of a more permanent solution... Shipping here takes way too long. It's the correct long term fix (and I'll do it) but I need something to keep this thing moving for a few weeks until the parts get here.

and I also need a nap. I'm tired. Thank you so much everyone, I owe you all big time!

See, something stupid.

For now just wrap electrical tape around the shaft until you get a good fit.