hey yellowbenz,

i think 77 is pre bowden, but im not sure.

I do know the haynes will not be helpful here. someone needs to chime in who has some experience with the earlier transmissions.

Ill be watching and ill chime in if I can help.

dd

1978 300D Non-Vacuum Trans
 

Long time reader first time poster.

Kevin,

I also have a 1978 300D and I am fairly certain that I have a Non-vacuum modulated Trans as well. I found two treads related to the topic.

http://www.peachparts.com/shopforum/tech-help/97353-my-transmission.html?referrerid=44341

http://www.peachparts.com/shopforum/diesel-discussion/93606-1978-300d-transmission-non-vacuum-modulator-adjustment.html?referrerid=44341

Not much to go on but it appears that there is a modulator, also the Haynes guide mentions an adjustment to a connection on the throttle linkage something about a spring and telling the transmission throttle position. When I get my guide back Ill look it up. Some one else on this thread very well may chime in on that before I get the chance though.

My experience has been that when cold the trany shifts a bit firmer, mine is also sensitive to fluid level, If yours has not had a fluid and filter change in a while it really helped mine out.

I drained some fluid out and ran a can of Trans-x for a bout a week then did the filter change and drained the torque converter to. I added a little Lucas trans fluid with the new stuff and it made a big difference in shift quality.

I hope that helps a little bit.
Dory
1979 300D

I know my signature needs updating
Oh and I do not work for Lucas or Trans-x

Thanks, I appreciate the replies. I haven't really paid alot of attention to the posts on auto's because I only owned manuals. When I started to troubleshoot this cars trans issues it became apparent that the posts I'd read didn't really apply to this car apparently.

Kevin
1979 240D manual
1978 300D auto

Update and more questions...
 

Good afternoon,

I have come a long way on my car since I first started posting on this thread year ago. I have fixed so many things around the car but the transmission on still no good - and I have a better understanding of what's going on:

Symptoms:
- 1-2 shift slips when accelerating hard, and clunks out of and into gear
- 2-3 is hard
- 3-4 is hard too

Info:
-vacuum signals are correct, above observations come with a lot of vacuum (15mm Hg at idle)
-new modulator is correctly adjusted to 50 psi hydraulic pressure
-fluid and filter done recently

So any idea what to do now? It seems like my system doesn't respond to changing the vacuum all that much. From what I have read over the past year I should be flaring all over the place with 15mmHg at idle. No matter what I do I cant get the other gears to shift mushy.

I am finding myself mentally pricing rebuilt tranny :-(

thanks, dd

You mention....."new modulator"?? Has this been recently replaced?

I'm still out here DieselDan44
 

Dan,
I don't write much on the forum these days... having too much fun actually working our extended family's fleet of 3 MBZ diesels.
Q - Tell us [IF you know]... how many miles on that tranny?
IF you don't know, give us your VIN and # off the tranny and I'll see IF I can verify IF it came with the car.
Now I see... your 82' 300D has 200K+ miles and IF that's the car/tranny and the tranny is original, she might have some life left... but that largely depends upon how much TLC she received over the years!
Regards,

Yes. Modulator and pin behind modulator replaced a year ago, but that less than 1k miles back. It holds vacuum and has the correct pressure set.

I think the tranny has 200k. I have to get down there to get the serial #, but I suspect it to be original.

TLC received - Im pretty sure until I got it, zero :-)

My 85 Diesel Turbo shifts from 2-3 really hard, like slamming into the gear.
What should I be checking??Do you guys have any pics??
I'm kinda confused because I have read all kinds of things!
Where to start?

Why not reduce modulator pressure a bit..........if you've got no flaring...........and see how it performs?

Thanks Brian...Ill give it a try.

What I do have is slipping between 1-2 under hard accel.

dd

When you say "slipping" do you actually mean "flaring"??

We need some information from ya...
 

As the Bloke who started this long THREAD I still need to know:
So:
Q1 - Do you have a vacuum gauge?
Q2 - What is the vacuum at the "T" that branches off to the Engine/Tranny control system... branches off the main Vacuum Pump -to- Brake booster reservoir chamber?
Q3 - Have you checked the vacuum line and fittings on your engine/tranny vacuum control system?
Q4 - What about the other vacuum using systems/components... done any checking for leaks?

Unless you have a California 1985 "300DT", the correct vacuum control diagram for it is: http://www.peterschmid.com/vacuum/1977_1985/617_95/1984_1985.jpg

These are touchy control systems and yours is a later model vintage car so the controls are a bit more complicated. I just hope you don't have a CALIF car.

Q5 - What's the VIN off your car?

Regards,

Well Im fuzzy on the difference between the two...heres what happens...

- accel hard
- goes to shift to second, feel the trans disengage gears hard, feels kind of like it has shifted to second (NOT soft or mushy), but RPMs dont decrease
- keeps moving through the accel fine, rpms dont rev high like a flare or bad slip
-once rpms come down from the hard accel, finishes the shift (hard) into second (again, NOT soft or mushy)

This gap in time last as long as the engine stay above 2.5k rpms or so.

A flare i've taken as means when the rpms hugely rev like on a standard when the clutch is going, an the subsequent shifting isnt hard but mushy.

whatever it is, the symptoms have me confused - they dont match anything Ive seen reported in my now extensive reading on the subject here.

dd

You've definitely got some confusion here.

Flaring requires the transmission to let go of the lower gear and fail to engage the higher gear..........as if it's gone to neutral between gears..........the tach climbs dramatically and the driver instinctively lifts the pedal...........and it upshifts.

One rather unique characteristic of these automatics is the tendency for the tach to remain at a given engine speed during mid power shifts. I cannot explain it, but have observed similar behavior on these. You accelerate at 2500 rpm in first and the tach doesn't drop on the 1-2 shift, although you could swear that the engine drops in revs.

When you notice the shift..........I'll bet the 1-2 has been completed a long time ago and you are now observing the 2-3 shift. It's not possible for the transmission to hang up between two gears unless it flares (as defined above).

So, kindly check again. See if you're confusing proper 1-2 and 2-3 shifts with a "slip" that you've identified as a 1-2.

I would like to chime in here, have been following these posts closely.
I have a W201, 2.5 turbo with auto. When engaging into D, there is delay, and then hard engagement, sometimes it takes about 5 seconds to do this. 1-2 shift ok, 2-3 shift flares a bit and 3-4 shift flares a lot. If I shift manually, it is fine, and also ok under hard acceleration.
Modulator valve and the pin behind it were changed a month ago (the pin was broken).

I went to Peter Schmid's website to find the vacuum diagram but there is none for a W201. Does anyone have one?

I have been told to check the vacuum, but don't know where. Can the vacuum amplifier be at fault? How do I diagnose this component?

Data
 

Brian,

I have some data...on the topic of backing off the modulator:

-I changed my modulator pressure from 50 psi where it was (at spec) and backed off 2/3 of a turn to try to achieve softer shifts. No change.
-backed off another 1 1/3 turn for a full two turns down from spec. No change .... still shifting fairly hard. Maybe it softened just a touch, but I think I should get a lot of softening with two turns of the modulator. With my current 12 mmHg at idle I should be flaring all over the place.

When I was setting my modulator pressure with the gauge I DID verify that my modulator valve was operating correctly - moving the pin did result in pressure changes - so I know the internal pressure is changing one way or another.

As far as my 1-2 goes I think it indeed is flaring, but not by much. I can hear the RPMs increase somewhat, but the tach stays steady, like you described when observing correct upshifts. I continue checking to verify this, I'm not 100% sure yet. I cant find a good spot where I can go from a dead stop to 60mph to count all the gears and verify its not stack shifting to 1-2 then 2-3 right away.

I dont understand how this failmode is happening, and its starting to get to me after a year :-)

Thank you,
dd

Something is amiss within that modulator. No change in shift characterics with reduced modulator pressure and no change with increased vacuum.

It's not performing correctly and I suspect that it's internal to the trans in some fashion.

At this point, it would be beneficial if someone else.........familiar with the vehicle........could drive it. You are at the point where you're second guessing yourself...........and I understand it perfectly. I've been there myself.

Thanks Brian. Ill take it to an indy around here whos reputable to be good. Its time.

I'll start mentally preparing myself for at least a new valve body and likely a new transmission, so that way anything less will be marvelous :-)

Be very careful. It's entirely possible that you know more about the machine than they do. They cannot make any more adjustments than you have already made..........and would need to have a thorough knowledge of the transmission internals..........a truly rare individual.

Would I be better off seeking out a shop that deals specifically with auto transmission rather than an indy who deals in MB's? I know that indys tend to want to just swap the unit rather than dive into the rathole of diagnosing the true internal issue. Sadly I dont have a trusted MB indy specialist...

Is there someone around here on MShop who is a 722.315 transmission internals guru who could sort of outline what may be the problem?

The problem is that you need a shop that's familiar with M/B auto transmissions and desires to find the problem rather than simply stating "duh.....you need a rebuilt".

In this day and age........nobody wants to make the effort anymore........sad to say.

Transmichigan
 

Brian is indeed right. There are few people who will take the time to search out and understand a problem, whereas there are too many who simply are doing their job, pressing the buttons, turning the cranks, etc.

An additional challenge is that the time needed to R&R a Mercedes transmission is significant, especially at current labor rates of $100/hour in many urban areas. For my '96, the R&R time is 6 or 7 hours. It's hard to justify doing less than a complete overhaul on a transmission, unless it has very low miles (in which case it shouldn't have a problem anyway).

In the case of my front pump leak problem, the transmission has 249000 miles on it and the leak is getting worse, day by day. Although it's possible to replace just the leaking seals, there are other seals that could also begin leaking some day, which must be removed from the inside (the tranny must be disassembled). Then there are the clutch packs and bushings that gradually wear out. Replacing just the leaking seals would end up costing me $1000 and I would still have an old transmission with 249000 miles on it.

Unless something else happens before next Monday, I'm taking the car to Santa Rosa Hydramatic. I've used these people before, they did an excellent job with my last American car, an '89 Oldsmobile. They work on Mercedes and other European transmissions regularly for many of our local independent mechanics. Their work comes with a two-year warranty and they're not nit-pickers as to the exact date. This is not cheap -- it will cost me about $3000, a sum that I had in mind when I bought the car (just didn't expect it so soon).

My other option would be a transmission from Peter Schmid or one of the other rebuilders. I'm getting a quote on that from my indy and expect it to be about the same price, maybe a little less. This would be an "assembly line" rebuild, which I inherently suspect to be not quite as good as a "hand built" job. This is not to criticize Peter Schmid, since I have never purchased one of his jobs, although I suspect my '85 has one, put in by the PO, and it has been trouble-free (40000+ miles so far).

In your case, dieseldan, the problem is to find someone who knows how to test and adjust your vacuum system and Bowden cable so that it provides the correct signal to the transmission. As Sam said when he began this thread, it's a critical adjustment. The transmission adjustments won't do any good if the tranny isn't getting the right "messages" from the engine.

It is possible that a transmission shop might know how to do this. The challenge is made even greater by the fact that the transmissions are made to work with gassers; diesels must mimic the way a gasoline engine's intake manifold works, hence all of the vacuum controllers and plumbing under the hood. You need someone who understands diesels as well as transmissions and that is not easy to find.

Jeremy

I have never adjusted the modulator that way...
 

DieselDan44,
I understand that adjusting the modulator by pressure gauge reading the internal pressure, but I have never adjusted it this way. the modulator setting according to internal hydraulic the pressure... but IF this were my tranny, before I would give up on her, I would try this method of adjustment:
On my last modulator adjust, without running the car, I turned the modulator key all the way in until it stopped and then counted the # of turns it took to back it out until it ran out of threads... I actually did this with the modulator OFF the car but this shouldn't be necessary. Then I parked the adjuster mid-way and adjusted in or out from that point... in to harden the shift and out to soften it... but my initial adjustments were "healthy" [ at least 3 full turns each ] adjustments until I saw change and then I reduced how much of a change [1 or 2 turns ] I made and then finally a fraction of a turn. I think mine has 8 "clicks" per 360 degree rotation!
At this point what can you loose?
Regards,

The issue is not the external adjustments or the modulator pressure. There is more than enough information from the forum to make the proper adjustments.......probably better than most shops.

The problem is that the transmission is not responding to the vacuum or the modulator pressure adjustments. This makes it an internal problem and most likely related to the recently replaced modulator.

Brian,

If I disconnected my vac entirely, and I just got hard, even shifts with no slipping, flaring etc, would that indicate replacing the valve body with a rebuilt unit? Im just thinking out loud here...

I havent yet found someone I feel comfortable taking my tranny issues to yet. No one I have talked to has been familiar with the diesel vac system. There is a place near boston that has a placard 'Mercedes Diesel Center', I think Ill try there next :-)

dd

Am I correct in remembering a kit that R/R(es) Springs...
 

Brian [& DieselDan44],
Am I correct in remembering that MBZ or one of the aftermarket sources has a kit that R/R(es) some springs internal to one series of trannies in one of the vintage W123 models... "K" something I think maybe?
After dinner I will do the necessary search to see what that was about... and IF this looks like an appropriate fix and you [Dan] are willing to "go for it", I think I have the kit and willing to part with it free.
Regards,

If you disconnect the vac entirely, and the modulator responds with very firm shifts with no flaring..........we can work with that...........the modulator is functioning. But, in your case, we don't get any response by the modulator when vacuum is added or reduced, so, that's the fundamental problem.

Correct.........we're more familiar with the system than any mechanic. What you need is someone familiar with the transmission..........the modulator's failure to respond to variable vacuum and variable pressure is the fundamental problem.

That would be K1 spring kit. I was about to ask how Fastlane has it listed, because it's not listed as the K1 spring kit.

This happens to mine. although I don't have a tach, so by engine sound. Sometimes lifting doesn't always get the upshift, and especially in 4th it flares several times while trying to get into gear. What can I do about it?

The first thing to do is to see what the vacuum level is going to the transmission at idle. If it's higher than necessary, an adjustment will often improve the situation. If it doesn't, the Superior spring kit seems to be quite a good solution.

This thread might also be helpful. The superior spring kit is listed in it. If the K-1 kit is all you need, keefstr has one he will sell you.

http://www.peachparts.com/shopforum/search.php?searchid=1825459

John

Your link is in error for me... learn a better way to SEARCH this FORUM !
 

Sorry John but your link above is NOT working for me right now anyhow!?
I have learned a new way to more effectively search ALLof the MercedesShop.Com WebSite using the power of the "advanced" Google features and so this seemed a good time to promote it. You can access this "advanced" feature by going to the normal Google.Com WebSite and then look to the upper-right of the search input box for "Advanced Search". Click on this and start learning. I usually use only a couple of the multitude of advanced input features... so for this case as an example I would do the following:
In the upper-most input box labeled:
" Find results with all of the words" I input [ K-1 spring p/n ]
and then in one other box mid way down the screen labeled:
" Domain [Only] return results from the site or domain" I input
[ www.peachparts.Com ] "
And so in this case when we click on the "[Google Search]" box our advanced SEARCH input ends up looking like:
" K1 spring p/n site:www.peachparts.com " on/in the normal/regular Google Search box... and with these four terms you get only 6 "hits". IF this # of hits were too large, you can add additional search terms to further reduce this # of hits.
Believe me when I say that this is far better than the usual search results using the FORUM's search features which appears to be limited as to how many search terms you can use!
In this case - it shows a hit that is:
Brian Carlton on 04-09-2006 at 04:32 PM POSTed that the part # is:
p/n:126 270 44 77.
Sorry IF my POST was a bit long-winded, but believe me "Google Advanced"... even "Google Not-So-Adveanced" is worth learning about to better find information on this, our favorite MBZ FORUM WebSite!
Regards

Sam;

If you click on the search tab at the top of the forum, you will then see a "google search" area to enter your query. I just tried it by entering "superior spring kit" and several shop forum threads with the info popped up.

Pretty neat. Someone else had mentioned a while back that the shop forum now had google, first time I attempted it. It won't be the last.

John ;)

Out of touch I guess...!
 

John,
Thanks for the update... this is proof that I have been working more on my and my Son's W123(s) than banging the keyboard contributing to this FORUM ! I just went through the experience of replacing all 5 of the engine suspension parts [ 4 engine mounts & 1 engine shock] and my 240D milkshake machine is no more!
Regards,

Sam;

Wish I lived closer, I would bring my two vehicles over to your shop so an "experienced mechanic" could give me a hand.

Ever dealt with the rear window defroster? I may have to add an aftermarket window grid to my 300SD.

John :D

From tranny shifting to defrosters... !?
 

John,
This is a common failure for this vintage MBZ(s) for the heater elements are glued to the inside surface and thus don't transfer the heat away very well and eventually due to moisture of "fogging' on the interior surface where they reside, their protective coating eventually breaks down... then corrosion sets in and then you begin to loose the horrizontal heater elements one at a time. I think the German design engineers correctly and purposely labeled these as De"foggers" NOT "defrosters" because I don't think they could ever handle the task of tru ice/frost removal on the outside of the window... only fog on the inside surface and this moisture doomed these systems... IMHO!
Being here in temperate CA, I decided it was NOT worth the replacement of the window just to have something I rarely ever needed! Yes, I looked into making repairs of these surface elements and when I had the rear window out to replace the weather seal I looked very closely and found ALL of the horizontal elements were no longer conducting... so mine still do not work.
I know where you are you really need a true "Defroster" system so IF you could find an upgraded rear window with the heater elements embedded between multiple layers of glass, then you might go for it IF the price is not too great... but finding such glass is a big IF I suspect!
Regards,

Thanks. I have a 123, just want to make sure it's the same because the links are for 126s.



It's at 12.5.

A quick test to determine if a vacuum adjustment will solve the flaring is to disconnect entirely the vacuum line going to the tranmissionn modulator and take if for a drive. If your shifts firm up, then you'll now an adjustment is likely to fix the problem. On my SD, I found disconnecting and leaving the line disconnected gave me the shifts I wanted.

Interesting, I will try this. :)

I got tired of playing with different sizes of orifices so I installed a 1/4" needle valve in place of. Also I burned out the restriction in the Tee where the vacuum comes off the brake booster line and installed a needle valve there as well. Now I can tune the vacuum requirements to a T. Trani is as smooth as velvet in every shift. Have K1 kit as well.

Good on you "The Gears"
 

As the guy who started this THREAD so long ago and in my early POSTS spoke of how these cheap restricted orifices were the German’s way of fine tuning these cars as they came off the line and readied for shipment… let me compliment you for your innovation in using a needle valve.

I have watched many times as my Mercedes INDY mechanic friend punched a stiff wire through the restricted orifices that are integral to the "Tees" that branch off the main vacuum line supplying vacuum to the engine/tranny control systems and other vacuum using components… and the Safety Engineer that I am flinched for I still contend that we must be careful NOT to open up these restrictions too much for this could starve the power brake booster system of some of its “power/boost” and that would not be good in an emergency where a vacuum line close to one of these “Tees” ruptured. So I compliment you for coming up with a way to fine tune the amount of vacuum being supplied to these control systems that are much less important than the brakes! I would caution you to try another innovation that has been discussed… namely to install cheap clear plastic paper in-line fuel filters upstream in these various vacuum lines so that dirt does not get into the system, carry down, and clog up your vacuum regulating needle valve and thus cause an imbalance and poor shifting again. I first installed a fuel filter on the vent line that goes through the firewall and terminated open under the dash. Next I put one on the IP shut-off vacuum device and routed it so that it was readily visible in the engine compartment… this to serve as an early detection of the oil that would be sucked along this vacuum line IF the shut-off device’s diaphragm were to begin to leak. Finally I put one in a visible location on the vacuum line that runs down to the tranny modulator. All of these are to help keep debris out of the system and thus clogging the orifices/needle valves on their way to being sucked towards the vacuum pump. In your case, I would put an in-line filter just before your needle valve!

Now... can you describe this needle valve... make/model/source/$??

Good on ya,

I have all the above tranny shifting problems with my beater benz 83 300D turbodiesel and am completely mechanically inept. I have already discovered in 9 months of ownership that most mechanics in my area are grossly inept. Does anyone have a reference for a competent indy within reasonable driving distance of Roswell, NM?

Hi Samuel.
The valve is from an Auto Supply store, about 15 bucks. It takes 1/4" copper tube in compression fittings. Real easy, 2" of tube on each end. A 1/8 turn will make a noticeable difference in the shift.
Use a hot wire or drill bit to open the Tee orifice. Don't want drill chips in the vacuum pump valve

I thought you might have used a 1/4" x 1/4" straight thru valve...
 

Yes, I thought you probably used a 1/4" x 1/4" straight thru model "needle valve". I saw these at my local ACE Hardware for ~$8-9.00. Your comment about it being sensitive to the point that 1/8 turn makes a considerable difference does not surprise me... even IF you opened up the orifice in the "Tee" coming off the pump-to-brake assist reservoir. For this very reason I think I will try to find a 1/8" or 3/16" needle valve of a design that gives more precise control.

This, possibly in combination with using a restricted orifice, might give me the best of both worlds... more precise adjustability AND a vacuum control system that will NOT starve the vacuum brake booster too much IF it ruptures out on some mountain road! I think this is one of the things the car's German designers had in mind when they used the restricted orifices in the first place. The various sizes of orifices were a necessity to fine tune to the subtleties of each engine coming off the production line. I think I am supported in this belief by the fact that they later designed the models after our W123(s) with a separate electrically powered vaccum system for the door-lock system which is one of the most likely vacuum systems to cause a major loss of vacuum... this because the system works the buns off of the 5 vacuum elements every time you lock and/or open the doors !

I'll let the readers of this my aging THREAD know how well a smaller needle valve works for me. Together with filters to catch the dust/dirt that gets into this vacuum control system... this adjustible vacuum control valve should make it a lot easier to set up these transmission shifter control system.
Regards,

Sam;

Please post some pics with the details of how and where you mounted the needle valves. Kudos to TheGear for thinking of this.

Could you also post some pics and details of how you installed the in line vacuum filters?

Merry Christmas.

John

That's an answer I've been looking for, for a while. Remove T's that go to valve cover...connect left and right sides together.

I think one of the "T" connectors is on the IP though, I guess I can just plug the end of it up instead of trying to remove.

It'll work on my '83 with EGR, yeah?

You're not looking for that answer.......because it's not meant for you.

The vacuum system for the 616 is different than the 617 and, typically, you cannot remove the transmission control lines from the valve cover 3-2 switches.

D'oh :( I'll just BB the EGR and keep at it then.

Your 616 can be replumbed slightly to eliminate two of the lines to the plug.........the EGR controls. But, you cannot eliminate all the lines in most 616 configurations.