Calling transmission gurus: 1980 300td with 722.1 won't go into 2nd
 

I have posted some of this before in other threads, but the subject wasn't as focused as it might have been. So here is my last crack at it:

1. My 1980 has the "vacuum-only" transmission. No linkage connected to the throttle. When I got the car last fall it revved way to high to shift into 2nd, then stack-shifted into 3 immediately.

2. The car had sat for some time so I decided to drive it a bit before looking into the shifting. After a few days it suddenly started shifting much better when warmed up, just a bit of slip into 3.

3. Then without warning it stopped going into 2nd. Winds up in 1st and if you back off the throttle it just loses drive entirely until you slow down a bit. Then gives a slippy first. If you roll to a stop it goes back nicely into first.

4. I checked the main vacuum line and output was low. Changed the pump diaphragm this weekend, turned out the old one was probably fine but was installed wrong side in and the cover was barely locked in place. Road test, no difference. Tried swapping around vacuum lines in case they were misrouted (there is a post in this somewhere). Road test, no diff.

5. Then installed a new vacuum splitter valve (the white valve on the VC). Road test, no difference. At this point the predicted fine day turned into a nasty afternoon of thundersorms so that was it for the weekend.

6. The buddy who was helping me (he having small hands, me not) wants to try switching over the modulator valve from my parts tranny, next weekend. I figure at this point it's a waste of effort.

In need of ideas. Maybe I should just swap in the known good 'regular' used tranny from my old 240d, and install the linkages to make it work. This is getting very old and the car needs much other attention that I'm not getting to....

Thanks

I wouldn't do any parts swapping without monitoring the actual vacuum levels going to the transmission. T into the line going to the transmission, hook a mityvac into it and run the mityvac out the hood at the cowl and shut the hood, leaving the mity vac gauge visible thru the windshield. Drive around monitoring the vacuum level and report back the levels you are finding. Without knowing what amount of vacuum is going to the transmission you're just shooting in the dark.

First check to see if your modulator holds vacuum. If it does not leak, then do what Kerry suggests.

Vacuum to the modulator is a factor in how the transmission shifts, not whether it shifts.

What controls whether the transmission shifts?

Remember this trans has no Bowden cable or throttle linkage connection.

So what controls it?

I have asked this before, in relation to THIS particular trans, but got no response....

Tks

Is that the case on the 'vacuum only' transmission?

Nail. Head. Bang. THANK YOU.

If vacuum isn't controlling it, what is, some sort of internal governor?

I'll try and answer this for you. I'm still leafing through the ATSG manual... unfortunately as I said before it is written for the transmissions that are fitted with the regulating pressure lever linkages that join to the throttle linkages.

My guess at the moment is that it is done by the "extra" valves in the valve body that I couldn't identify when I took it to bits...

I've nearly finished my write up - though I now feel obliged to write about how the sodding thing works!

Take a look at the other thread - could be B1...

When you accelerate hard in 1st gear, does the speedo register?
If NOT, possibly the nut on the output flange could be loose.
Then the governor will not work as well.

Yes it's working normally.

Tks

Aha
 

Found this interesting thread....

http://www.peachparts.com/shopforum/diesel-discussion/193291-722-118-first-gear-only.html?highlight=installing+modulator

This would suggest the modulator does have a bigger role on this model of transmission.

The last entry also mentions the governor.

I am really really confused Zacharias...
 

Please can you tell me what is going on?

In this thread you are saying that the transmission is stuck in first

but

In this thread you say it isn't

http://www.peachparts.com/shopforum/2775406-post11.html

I don't get it.

Is there any chance you can make a video?

By the way as for the last comment in this thread:-

http://www.peachparts.com/shopforum/diesel-discussion/193291-722-118-first-gear-only.html?highlight=installing+modulator

I don't see how you could reach the governor from the outside of the transmission. You can pull out the secondary pump but that's as far as I can see anyone getting

http://www.peachparts.com/shopforum/diesel-discussion/301783-722-1-secondary-pump-special-tool.html

Condensed info:
http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1597891-diy-w123-transmission-diagnose-adjustment-722-a.html

I have an '81 240d, vacuum only transmission.
My modulator was leaking, pulling up transmission fluid into the vacuum line preventing vacuum from reaching the modulator.

To shift properly it rev'ed up and I had to back off the pedal and it would shift hard into gears.

New modulator fixed it.

Previous to this I managed to drive Mercedes for 15 years with my knowledge of their auto transmissions being an ability to distinguish which piece is the TC. I imagine most people on this list are similar.

My lack of precision in my language describing a problem no doubt reflects a pitiful lack of understanding of what goes on inside an auto trans.

So here goes:

When you take off it winds up in first. I have taken it to just before the warning dot on the speedo and it does not shift up.

If you take it to near the warning dot and back off the pedal it slips into neutral until the road speed decreases, then it engages first again.

I did say before it was going into second and slipping, but either I was mistaken or that is no longer the case. On the weekend I drove it further than I had attempted previously and I only had forward drive in first. However on previous occasions I was sure I had some very limited forward drive when I backed off the throttle, albeit with HUGE slippage.

By the way it engages both drive and reverse instantly from a stop. No hesitation.

If you want other info, please ask specific questions.

You need to monitor the vacuum levels before doing anything else and then report the numbers here.

Yes I had caught your comment before.

I should be able to do that either tonight or tomorrow sometime.

Tks

Right - well that's that then. I'm glad we have now ascertained that it only works in first and reverse.

However:-

I'll shut up and wait for the vacuum numbers!

(On a personal note Zacharias I didn't mean to be irritating I was and still am trying to help - do it Kerry's way then hopefully there won't be so much messing about)

Ah yes, sorry to bite your head off but eating a variety of drugs for lower back pain/sciatica since the weekend leaves me a bit, uh, jumpy at times....

I just got ***** at work for an email I sent yesterday :eek:

Okay, vacuum report:

Modulator: holds vacuum, does not leak down at all. Tried it multiple times.

Driving: I got fluctuating readings at idle. Started off showing 8 in/hg at idle and 7 under load (all the way up to about 22 mph). Then as car warmed up went up to 12-ish at idle, 7 under load. Then down 10/7. Then back to 8/7.

Gauge is brand new.

I did notice some oily residue around the connectors, which wasn't there on the weekend.

Were those numbers at the modulator line? What is the level in the systems as a whole?

That is what is going to the modulator line.

I did not measure the main line today but after the diaphragm replacement it was I believe 22. It was good.

I don't know what the numbers should be on a vacuum only transmission but they seem low to me. You could use the Mity Vac to pump up the levels to the transmission and then bleed it down, all while your driving to see if it makes a difference.

Can you tell me what you expected for numbers?

Something mimicking a gas engine like the VCV does on the trans with the bowden cable. Higher at idle and dropping to 0 at wide open acceleration.

Hmmm I wasn't exactly using WOT in first gear today.

There is mention in one of the threads of gently enlarging the opening at the T running from the main vacuum supply line. With the sort of low reading I got today, I am inclined to try that next.

I am a little curious about the modulator valve as well. I read two or three times in various threads that they should slowly bleed down. Mine holds its vacuum and doesn't bleed down at all.

I wouldn't enlarge the opening before determining whether increased vacuum improves the shifting by using a Mity Vac. At this point, nobody seems to know what the vacuum numbers should be on this transmission so experimenting with a Mity Vac is the only way I know of to see if the shifting can be improved by increasing or decreasing vacuum.

I hear you. Tonight or tomorrow.

Building a long enough extension to the vacuum lines to get them through into the cabin for MityVac is going to be a riot. :D

My vac gauge has a long hose so it wasn't such an issue.

Just buy a 6' piece of rubber vacuum hose at the parts store. You can use it now and when the vacuum system craps out, you can run a line from the shut off valve into the driver's seat so you can suck and shut off:)

Sounds like something out of Casino Royale (the original one) :D

Update:

1. Drove car with mityvac hooked up to modulator valve line. Pumped to various vacuum readings. No shifting.

2. Measured vacuum coming from T fitting out of main line, over to vacuum switch on VC. Only 15 in/hg.

3. Gently enlarged opening in T fitting. No difference.

4. Switched line to VC switch to supply it from the second fitting, which normally supplies rest of vacuum lines. It reads about 20. No difference.

5. Finally switched over modulator from spare transmission. Still no change. QUESTION: I read several posts on pulling the modulator and none of them said a word about the modulator being in contact with transmission fluid. When I pulled mine I got over a litre of leakage. Is this normal?

I'm about done with it... I think this treasure hunt is officially done.

Thanks to all who assisted.

Shame it isn't working out.

I'm pretty sure that these transmissions don't shift "on the vacuum" I think the vacuum still does the same job as other transmissions... these 722.118 transmissions just have extra bits in the valve body that do the job of the regulating pressure lever that would normally be poking out of the casing close to the B3 (reverse) brake band piston housing.

If you are willing to sit back and take a coffee break for the next few days then I really will have some good pictures to show you along with a write up for the rebuild of these transmissions...

...you could then decide whether you want to pull out the valve body (and with the safety of the pictures I'll post - which have been checked against 2 valve bodies!) clean it all up a bit.

I'm sorry for the delay. I've been meaning to get this DIY done for a long time now. It has turned into an automotive version of War and Peace. Brevity is not really something I do.

Clean the govenor
 

Hello all,
First post as I could not contain myself from suggesting that the OP should clean the govenor.I bought a w126 last winter with the exact symptoms
and this cured it completely.It is under a round easy to remove cover at the
rear of the transmission and can be done on the car.You will need to support the transmission as you loosen the driveshaft and remove the rear mount and maybe a cross member.This allows you to shift it over for a bit of clearance.
There will be a latch of some kind holding it in place so it will not come out as
until that is loosened. I saw two different styles in the 722.3 manual.You should not loose any significant fluid either so it is rather dry operation.
Soak it in solvent even if it seems clean.Then blow it dry.
I used a mixture of ATF and acetone and some marvel mystery oil for good measure.It did move before I soaked it but it moved easier after!
Apparently it was enough to keep the upshift from happening.The manuals list the govenor as a possible cause of " no upshift".

Good luck

If you had paid a little attention to the link I shared....

http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1597891-diy-w123-transmission-diagnose-adjustment-722-a.html

Now at this point you have messed so much with it that its probably not worth to try fixing, plus you are already frustrated.

This is a great source of information but the problem I have with it is that it is a bit too much information! I know I'm guilty of doing the same thing (giving too much information) but which bits do you feel would help the OP fix the problem?

I'm still not 100% sure of the symptoms the OP has with his transmission - but may be you have a better understanding...

...I would like to see this problem sorted out as I guess I'll be in the same boat when I get my car back together.

Hi skizikz...

...and welcome to the forum...

The OP has a 722.1 transmission. The governor is not as accessible on this transmission as it is on a 722.3

post # 1 is pretty simple to understand. Pretend to understand how the tranny works in a single day is just funny. It will take more reading than hands on, because the fix will probably be simple when you know how to find it. Otherwise, what happened in this thread is a good example of "building a house starting from the roof".

There is an "order" to do tranny diagnose, doing it backwards will probably fail or make it worse and more difficult to detect. Not to mention the waste of time and frustration.

I wrote that hoping to give others a guide to be able to diagnose properly.
Govert and me are there to answer questions, but first give us symptoms and what you have done from the listed procedures in post #1.

I hope we can figure the easiest way to improve shifting. :D

That last sentence is snide, inaccurate and unnecessary. Given the general tenor of this board, it's waaaay out of line.

I did my best to plow through the collection of material in that link. I appreciate you spent some time collating an online brick of material on transmission issues for the benefit of others. However, throwing brick-links out then yelling "fetch" does not constitute constructive input.

I see nothing in your link that advances the knowledge base on troubleshooting the vacuum-control-only transmission.

FYI I have done everything on your list of items to be checked, aside from messing with the VCV on the IP. I did look at that link and in the first few lines Greg states what that VCV troubleshooting is for, and it has nothing to do with the issues I am experiencing.

Oh and yes I only changed the fluid, not the filter. That was a matter of circumstances on a particular day. Though at this point I feel it's heroic measures, I will be happy to do so at first opportunity if anyone truly believes it will make a rat's butt of difference here....

I welcome any and all constructive input, but anything else can be kept to one's self.

Q: That last sentence is snide, inaccurate and unnecessary. Given the general tenor of this board, it's waaaay out of line.

O.K. I'm sorry you feel that way, I wasn't trying to hurt ur ego or feelings. I get that it could be read with different tones. Didn't think in reading it with a "jerk" tone. I wrote without thinking in the possibility of been sort of offensive. My apologies.

If you don't mind... who is Greg? what does "fetch" means?
Thanks.

-----
edit: LOL!:D never mind, I found "fetch" meaning:

"fetch :

Adj. Variation and shortening of the word 'fetching'. Used to describe something cool and trendy. General usage by females, teeny-boppers. You can almost hear it replied with "Like, totally!" Coined by the movie 'Mean Girls'.


"That new store, Siblings, is SO fetch!"

Ok just to inform all here. I have a 722.1 in my Sd. The only things hooked to it is the electronic kick down and the shifter and speedo cable. I have to manually up shift it if I don't want to shift at 2k every gear but everything works. No flairing at all. I do have harsh shifts and I'm keeping it that way to help keep the thing alive for a bit.

There is one thing I have noticed though. When my trans is hot ~200° and I floor it off the line (on the kick down button) it sometimes will not shift till 6000rpm.

So I'll get into my book tomorrow and find what is actuated for each gear. I still have a broken 722.1 that I'll dig through and see what I can come up with personally.

I think harsh shifts will eventually result in this sort of damage

http://www.peachparts.com/shopforum/diesel-discussion/297960-722-118-transmission-problems-stripped-out-splines.html

http://www.peachparts.com/shopforum/diesel-discussion/299729-advice-reqd-shaft-spline-wear-measurements-possible-fix-722-118-transmission.html

I don't know for sure but I've got a pretty good idea that the splines on the front planet gear system (and probably also on the middle planet too) just aren't up to the job...

As for data for shifting take a look at the information that is compiled over on Benz World =>

http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1597891-diy-w123-transmission-diagnose-adjustment-722-a.html

@Zacharius => The most recent posts might help see post #20 made by 1980-300D(bio) for example

Possibly, but I've already arranged to install another transmission. I have lots of other issues to deal with, on this car, and I am working outside with likely 4-6 weeks' possibility of decent weather left before it gets too cold and damp to work outside for someone with arthritis.

I commend your interest in getting to the bottom of this. But apart from all else, I frankly would rather have a transmission in the car that the community in general is more familiar with.

Good point.

I'll try and change that though!

Take some pictures of your fun in the last of the sun for this year...

"The OP has a 722.1 transmission. The governor is not as accessible on this transmission as it is on a 722.3 "

AHH, So it is a tear down?

Wherein I eat crow. Umm UMMM TASTY (NOT)
 

Fate is not without a sense of humour, apparently.

It turns out that my spare transmission is a 722.117. It has been sitting in the back yard under a tarp and I never examined it. (My car now has a .118.)

Now I find this fascinating, as my old 240d that it came from did not have the white vacuum valve on the VC. I know that. In fact, I am quite sure that I never had the modulator hooked up to vacuum on that car. It shifted beautifully, albeit late out first, but it was excellent otherwise.

And now for my really, really BIG slice of crow pie:

I finally pulled the pan on the transmission now in the car. At the bottom of the pan were metal shavings, one intact machine screw, the head of a second screw and some unidenfitied metallic pasty substance.

With what I found, I decided there was nothing to be lost pulling out the valve body, given that one screw was dangling out the side of it.... A rod that appears to have been repaired with JB Weld. The second screw, whose head has been badly chewed. More evidence of the pasty substance. I will attach pics later... right now I can't do it from this machine.

So yes, had I stuck to the routine, I would have been where I am now (given that I can only work on it on weekends) about month ago. :eek:

Nightmare - where are the pictures?

Are you looking for a .118 valve body now?

No I am going ahead and installing the other trans.

The machine screws did not come from the valve body as far as I can see. These are Phillips with tapered heads. The only screws visible on the sides of my valve body are flat heads.

It looks like they came from elsewhere and made their way down there. One is in good shape, the second is badly chewed, the third is just the head (again chewed). So they had an interesting and we can assume lethal journey through the trans.

The metallic paste really gives me pause.

I uninstalled some security software that had gone buggy and am now having browser issues. I can't upload the pics. If you PM me an email addy I will send them.

PM sent.

Those screws are most likely the three screws that hold the cover plate on the front input shaft just before the sun cog goes into the front planet assembly (I'm sure you know the one I mean!)...

...they are meant to be fixed in place with LOCTITE...

...I wonder what happens if you don't?

Long live gmail!
 

Here are the photos from Zacharias (sent via email to me)

http://www.peachparts.com/shopforum/...1&d=1315159335

Definitely the three screws for holding in the cover for the input shaft

http://www.peachparts.com/shopforum/...1&d=1315159353

The rod - which doesn't look too altered to me - though I've only opened three 722.1 transmissions so far.

Give that gunk a scrape and see if it reveals some shiny metal... it might be brazing - difficult to see... I'm keeping my fingers crossed - ever hopeful!

Assuming that is what they are, can you guess at the path they've taken and what they may have ruined?

Pics sent.