Transmission / driveline clunks, 3-4 shift flare, delay+clunk into R and D
 

Hi everyone. First let me thank this forum for being so helpful this far. I've had my '84 300D turbo (first time W123 owner) for less than a week and have learned so much from this great resource.

I have searched the forums and websites long and hard but I can't seem to find a concrete solution (or solutions) to my tranny problem.

First of all, when I shift from Park to Reverse or Drive, there is a substantial delay and then a hard CLUNK when it does shift. And when I let off the gas while driving, I can hear something clunk in the drivetrain. Fairly loud. There is no vibration when accelerating though, so I don't think it's a flex disc or support bearing (I don't think.) Diff mount maybe?

It also clunks when it downshifts coming to a stop, and the shift from 3-4 at any throttle input is much softer than it should be, and flares occasionally. I know that the 2-3 flare is common and fixable with the K1 spring kit, but my question is, would that kit fix this problem as well? I haven't yet pulled vacuum on all vital components of the system but I am getting there. The vacuum line from the little green check valve to that plastic valve on the injection pump is shot. That green valve may very well be shot too. I looked at the vac. valve levers on top of the engine and they don't look too bad. I think they still have a little life left.

I am going to change the trans fluid and filter tomorrow but I might hold off if anyone thinks I should try the K1 upgrade. 1-2 and 2-3 are bang on, and very crisp at WOT, but 3-4 is the problem area.

I'm pretty sure there is a vacuum issue somewhere about the car. The door locks can be finicky and very very slow at times. Sometimes the RR door doesn't even lock when I lock them. I'm starting to think that little yellow check valve may be leaking too, it looks like its the original one haha.

Any help is much appreciated,
By the way these cars ROCK!

Patrick

re
 

^^^

Fill in your "Signature"...
 

a little more thoroughly... somewhat like mine below, and this will tell us the important mileage numbers your car, tranny etc. have on them.

re
 

Done. Thanks for the advice. :) I've done a little more looking at it seems this could be a B2 piston problem. Or is that just totally inaccurate.

The thing I am most worried about is the severe clunking when I let off the gas.

Patrick

how hard is it clunking?
 

Ours just had the drive shaft bearing and rear tranny mount done.
Before it was fixed, when it kicked down, the drive shaft popped into the floor boards. It wasnt so good. It was really loud and violent. It wasnt too bad under acceleration compared to how obvious in was dunring deceleration.

It drives ALOT more smoothly now. It is a little lumpy but I cant really tell- I haven't driven enough Mercedes 300D's to know if it was right, or or needed tweaking.

i had a clunk when i would put my car in reverse and drive backwards. that was a bad rear axle. after replacing that, i had no more issues. just food for thought.

Check the differential gear-0il level 1st...
 

When we took possession of our 1980 300D, I found the rear-End gear oil only ~half full... so be sure to check this... and consider trying a heavier oil as a diagnostic test as to this being worn differential gears!
Regards,

Check your flex disc's, transmission mount and differential mount as well.

Check Vacuum
 

You indicated a need to check vacuum. I believe this is your biggest contributor to off-throttle downshift 'clunking'

Get a vacuum guage and see if you can pull vacuum on the line going down to your transmission.

Mine was not connected, when I did connect with new tubing it would pull vacuum but not hold vacuum for very long. Shifts are smoother now under throttle but can still clunk off-throttle.

Reverse and drive clunking when shifting into gear - I defer to previous posters - rear axle/diff???

My Transmission Problems
 

I'm also currently having transmission problems with my 83 300DT. It has 280K miles and here are the problems.

The biggest issue is every now and then when going up a very steep hill the transmission will completely slip ( this could happen when the car has been warmed up or cold, but usually more likely when cold). The shift lever is really loose and usually I have to take is it out of gear and reshift back into Drive.

It feels like even the power output (when it initially slips and I put it back into gear) is not as great as it should be. it doesn't really grab the road, and its like the torque coming up the hill has been downgraded. it almost sounds like its slipping but my RPMS don't go through the roof or anything, I can only describe it as not as much torque. sometimes to shift the car into its last gear I have to bring the shift lever obove drive almost in between N and D. shift lever linkage is deff in need of some help.

usually I have problems, (the car not pulling up a hill good) when I have to start out from a stop. its interesting because the car is sluggest at slow speeds (Pickup isn't what it should be) but the turbo is deff working while I'm on the highway and seems to kick in later at around 70 MPH or so. I've owned other 300DT. my previous deff didn't feel as sluggish off the gate. I don't think its the turbo boost sensor. I cleaned the banjo and replaced the line, and the turbo is deff working on highways and higher speeds, where shifting isn't needed. The other issue with the vehicle is a low vacuum condition. when I drive the vehicle when its cold (engine, after it sits overnight ) I don't have any brakes. usually once vacuum picks up, usually in about 15 seconds, breaks are fine. (I recently preplace my brake booster and before that didn't have any vacuum assisted brakes). So I guess my question here would be could low vacuum suction to the vacuum modultor cause poor torque conditions to the transmission? I'm going flush the transfluid and replace the filter and all that stuff. shifting and power deff improves/increases once the vehicle is warmed up.
The only other piece of the puzzle I would like to add is this. When usually cold and when I try and hammer the car, you know really hit the gas the vehicle surges, almost feels like the engine is reving to 3000 rpms then backing off. at first I thought this was an engine issue, but now I'm thinking its the trans slipping real quick then ingaging again. it does this especially when going up a hill (thats when its not completing slipping and I have to reset the shift lever) doesn't usually do these high quick bursts of hi revs when warmed up.

Vehicle shifts good when warmed up , and transmission problems aren't very noticable at operating temp conditions. I guess the transfluid is thinner/hotter.

In my head I'm thinking the possible issues are:

1 ) torque converters, do these go out on these cars? are there any similarities between my car and a bad converter?

2) vacuum modulator/ low vacuum condition. thow doesn't this just control shift points? hard shift does occur at times, sometimes it shifts nice and smooth.

3) shift linkage just being out of wack and inbetween gears, if this is possible. my cars shift lever is deff the loosest I've felt in one of these cars

Thanks for any advice you may add.
Ben.

Ditto "Running-Snail "s above and a little more FREE advice too...
 

Ben,
Believe me when I say it's easy to spend a bunch of money on a fix-it transmission project by just throwing parts at your MBZ ! I wholeheartedly agree with " Running-Snail " above and also recommend you invest in a basic hand vacuum punp/gauge [ IF you haven't already ] and start what will most likely turn into IMPORTANT lessons learned about your MBZ's engine/tranny vacuum control system(s).

Next [ IF you haven't already ], read and gain a greater understanding of these engine/transmission vacuum control systems by reading Steve Brotherton's article at:
http://www.continentalimports.com/ser_ic20242.html and this should help you to sort through this mystery.
Next take a read of my THREAD at:
http://www.peachparts.com/shopforum/diesel-discussion/158216-its-critical-how-you-set-your-transmissions-vacuum-system-your-diesel-mbz.html?highlight=Critical
I don't think tranny " fix " is a " quickie " unfortunately so settle in and LEARN now for it will stead you well in the long run. No matter how much we on this forum might try to help you, IF I'm correct that this is not a simple " fix ", then YOU need to gain much more first-hand knowledge of this "CRITICAL" vacuum control/actuator system. A systematic step-by-step approach based upon a reasonably good knowledge of how these various vacuum components work... this will help you more in the long-run!
Regards,

re:
 

Thanks again everyone. I have read quite a bit of information about these systems, including Brotherton's extensive article. I guess the next step is a hand vacuum pump. The line going down to the trans vacuum actuator is the one just past the green dashpot right?

Patrick

[quote=Samuel M. Ross;1303988]Ben,
Believe me when I say it's easy to spend a bunch of money on a fix-it transmission project by just throwing parts at your MBZ ! I wholeheartedly agree with " Running-Snail " above and also recommend you invest in a basic hand vacuum punp/gauge [ IF you haven't already ] and start what will most likely turn into IMPORTANT lessons learned about your MBZ's engine/tranny vacuum control system(s).


great this sounds like a good idea. I'm deffinately not up to full speed on the scope of the vacuum control system and how it effects these transmissions. but I coud imagine if vacuum pump isn't pulling enouph vacuum in the beginning to assist in breaking what would it be doing to the tranny. I do have a gauge and I'm going to start testing vacuum at different points in the system.

Thanks.

We need to split things up guys!..........
 

OK guys, I'm not an official of this FORUM or anything but I sincerely suggest:

That you Ben [ aka = " Britten " ] start a new THREAD using much of what you included in your POST: http://www.peachparts.com/shopforum/1303929-post10.html
It's not fair to you Patrick [ aka = " pwalsh53 " ] for I think it is detrimental to both of your IF we try to help both of you on the same THREAD… for I feel it dilutes participation by those of us who want to give new users of the FORUM a hand.

Ben – I suggest you give us a final POST regarding your MBZ on this THREAD by giving us the title of your forthcoming new THREAD… I suggest something like: “Auto Transmission Problems – Please HELP! [1983 300D TurboDiesel ] ” this way those of us reading this [ Patrick’s THREAD] can easily recognize and add and monitor your [Ben’s] new THREAD to our automatic e-mail list... AND your THREAD title will be more informative in the future sitting there in the archives.

Otherwise I’m afraid both of you will NOT receive the attention/HELP you need.
Regards

re:
 

Thanks Sam.

As for my car, does anyone think I need the K1 spring kit? My transmission cross section is:

1-2 crisp and fine
2-3 just fine
3-4 always too soft (flares sometimes)
long delay and hard clunk into reverse
clunk when i let off the throttle
softer clunk when gears downshift

Anyone think I might need the K1 spring kit or B2 piston?

Patrick

re:
 

Update 1: Blocked off the vac lines going to the door locks (and shutoff valve incidentally) from right off the main brake booster line.

Result: Yep, locks stopped working as expected but trans problems are all still there. While I still suspect a small leak in the door lock system, I can now at least rule that out as being the cause of the transmission problems.

I'm thinking I'm going to get a hand vacuum pump this week and get to testing the trans vacuum system.

Question: the big vacuum distribution box on top of the valve cover (3/2 switch is it called?)...Ideally that should have three vacuum lines coming out, correct (84 non-CA turbodiesel)? Ok so two are coming out, and I blocked off the other one which went to the EGR. When I bought the car the line was broken anyway so I just stopped the vacuum leak.

So what about those other empty holes? Should they be plugged?

I'm beginning to think my problem is either with the green dashpot, trans modulator or the lines in between because I know the system is getting good vacuum from the pump, checked it the other day. Don't remember the number though.

Updates to follow...
Patrick

To answer your questions and points...
 

Patrick,
Until you get that pump/gauge, we will be stumbling a bit... but here are some comments that correspond to the "NOTES" I have inserted above into your last POST:
[<-Note-1] - the big vacuum distribution box on top of the valve cover (3/2 switch is it called?)... well to answer your question, lets call the big box what the diagram calls it... #64a and #64b which is the designers way of telling you that this is the " switchover valve " that switches off certain thing(s) at idle and other thing(s) at full throttle... and I canNOT remember which is when. But for now let's not worry about these for until you get your pump/gauge, you will not be able to test this multi-function vacuum switching valve. You might end up abandoning this valve anyway for one of the things being shut off is the EGR and until you decide you need this needless system, I recommend it be left out or until near the END of your repair project!
[<-Note-2] - Yes, I'm all-but-positive the switchover valve has only 3 vacuum lines in/out of it... and the other "stuff" you see illustrated on the diagram to the left side of #64... these are the internal pieces of the idle and full throttle vacuum switch-off parts of #64. When I blow up this diagram here and try to look close, the line that goes down and to the EGR, appears to be labeled #1 on the SwitchOver vavle... and the line that goes down and around to the "Y" or 3-way connector to the right of the VcV, this line, this line appears to come from #2 on the SwitchOver valve... and finally the line that goes directly to the right to two 3-way connectors [with the #63 written between them (a restricted orifice - more on these later)], #63 above the VcV & DashPot, well this line appears to be coming from #3 on the SwitchOver valve. I hope I did not confuse you with the above!?
Q1 - Do you see any numbers on the SwitchOver valve?

[<-Note-3] - For now you might want to either put golf "T"s to plug up these lines that are shown going to #2 & #3 on the SwitchOver... OR if these lines are no longer there, plug up the "T"s in the 3-way connectors where these lines are shown going to [described in Note 2 above].
[<-Note-4] - No way... see my THREAD:
http://www.peachparts.com/shopforum/diesel-discussion/167513-try-%93dashpot%94-your-pre-1981-auto-mercedes.html as it sort of explains the fine-tuning purpose of the green DashPot!
[<-Note-5] - No... the vacuum modulator [on the tranny] will not figure into this troubleshoot until we get the vacuum control components under the hood tested, working right, plugged off, balanced and/or working correctly with one another... and then the very last thing we will address is the vacuum modulator!

I hope all this has not confused you, but I thought I would respond to your specific question(s) and points in your last post... to get a jump on things as it were. Please expedite obtaining your vacuum pump/gauge combo!
Regards,

I'm trying to be kind here Patrick... but put plainly, it is premature to talk about the internals of the transmission before we finish troubleshooting the engine/tranny vacuum control system and then tweaking the vacuum modulator to get the tranny shifting its best with whatever improvements we make. And I might have a K1 or K2 spring kit I'll discount for you IF it turns you really need one.
Sorry IF I answered this one out of order!?
Regards,

re:
 

Not a problem at all, Sam. I really appreciate your help. Taking this project on with no prior knowledge of M-B was a challenge and you and this board have helped greatly in my education.

I have read through the big "how to fix your shifting" article on mbz.org that goes through chronological steps for diagnosing shifting problems. I am going to get a vac pump hopefully this week so I can get to testing. I intend to fix anything within the engine bay first.

Speaking of engine bays, I noticed today how the W123 hood can be partially unlatched and point straight up into the sky for easier access...love it. When I discovered it I remembered my friend's S420 had that exact same feature. Why can't BMW think of that one? ;)

Anyway, I shall keep everyone updated on the diagnosis. Currently the only things I have done are replace the crumbling vacuum hose between the green dashpot and the IP valve (which made the car turn off alot faster incidentally) and plug the EGR vacuum hole on the 3/2 valve.

Patrick

To clarify...
 

Patrick,
(1) To be certain that I am not misunderstood, IF you see any "crumbling" vacuum hose during the course of this troubleshoot project, you have my permission to replace it! As a matter-of-fact, you shoud go ahead and purchase a yard or two of vacuum hose... but make sure it fits the more plentiful size hard vacuum line you see under the hood!
(2) Something to keep in mind... I leave on Nov 1st for a 3-week trip out of the country and will not like have many opportunities to check my e-mail!
Regards,

re:
 

Okay, here we go.

Pulled some vacuum and such. Everything seems to hold vacuum just fine except for the brown line running through the firewall...not sure what this is yet. The door lock system seems to be fine. Which is strange cause sometimes the locks are slow or nonexistant after it's been parked for a while.

Also, the car was producing proper vacuum at idle and the trans got a signal of just over 10"Hg at idle and it went down to zero at WOT. Seems fine to me.

Anyway, I disconnected and removed all the EGR and 3/2 switchover stuff and made the appropriate connections because I believe the 3/2 setup was leaking. Things pretty much remained the same except a bit less clunking on downshifts.

Then I disconnected the line going down to the transmission. Now THERE are some downshift clunks, wow. Doing that made 1-2 and 2-3 a bit harder (since it thought it was getting full throttle without vacuum), but the 3-4 flare was still there in all its glory. So looks like we have an internal trans issue :(

Does anyone know where I should proceed from here? I am thinking I might do a fluid/filter change this weekend. Are there any of those B1 / B2 piston kits or K1 spring kits that usually fix a 3-4 flare? The downshift clunking is pretty much nonexistant and I have traced the other clunk (I think) to a worn diff or trans mount or driveshaft coupler. So the only real problem now is the 3-4 flare.

Thoughts?

Thanks!
Patrick

One more coment on vacuum. There is a black vacuum line that comes off that little white plastic thingamajig on top of the IP that goes through the firewall and connects to nothing. I coulndt figure out where it went so I plugged it. Afterwards it downshifted extremely hard making me think the differential was going bad. Later I learned this line is a vacuum release to leak off vacuum!

Interesting.

Well since I have found no serious leaks in the vacuum system even with the small leak plugged up from the brown line, and since unplugging the vacuum to the modulator didn't change the 3-4 flare at all, it's time to go internal.

I believe what I shall do next is install the Superior Shift kit and put a stronger spring on for the 3-4 shift (K2 I think) and maybe a softer one for 1-2 since it likes to fishtail a bit in the rain. In addition to this I'll change the fluid and filter at the same time.

Updates to come soon...

Once again my current situation is 1-2 hardish, 2-3 crisp but fine, 3-4 bad flare, delay and lurch into R and D.

Patrick

:(
 

Ok. Today I changed the fluid, filter, seal, and did the Superior Shift correction for the 3-4 shift.

Well, the clunks into R and D are pretty much gone, but it still flares. So I guess its just internal wear. :mad:

Oh well. Any other suggestions before I just decide to leave it?

Thanks!
Patrick

Be careful plugging those vacuum lines which seem to go nowhere. Could be just a simple vacuum vent line and needs to be left open. they usuall run inside the cabin and left open ended or as my 87 was had a filter in the line under the hood to protect the whole vacuum system from junk in the air. :D
Bud

Hows your kickdown cable?

re
 

Would the cable cause only one gear to mess up?

Patrick

Did you ever get a chance to figure out what was causing the 3-4 flaring?

Yes Patrick, you have kind of left us....
 

... left us hanging here. In re-reading your last few POSTs you seem determined to condem your tranny as having "internal" problems much too quickly... even after it improved after your fluid/filter service.

Bring us up-to-date and I hope that does not include your notice that you have just invested $2K or more in a rebuilt tranny [Dealer =~$4K+].

Regards,

I'm having the exact same problem with the 3/4 shift flare. It occurred after I changed the fluid/filter.:confused::confused::confused::confused:

Patrick. What's the status of your problem now? What's the latest update please?

Here are the specifics of my problem. I don't want to hijack your thread, so here's the link.

http://www.peachparts.com/shopforum/diesel-discussion/179646-3-4-flaring-after-fluid-filter-change-83-300d.html

Patrick???..where'd you go??

No Reverse or engine shut-off during cold weather
 

Hello everyone, thank you all for the wide range of good postings. I resently acquired a very expensive vehicle (1979 300D, 174,880 miles) for the bank breaking price of $175.00. The car's been sitting in a field for over 8 years, just one step to the junk yard until I stepped in. Well thanks to a fello diesel car driving friend and I, we got the engine started, that's all it took, now I'm hooked. Did some massive preventive maintenance, still have a few vacuum problems, especially when it's real cold outside. No reverse or able to shut off engine, except manually. I'm more concern about the transmission, I had it flushed out a week ago. It's always been sluggish, now no reverse. Anyone have any ideas how to isolate if it's a vacuum problem, (already have vacuum gun).

Tony

Flushing might have caused your loss of reverse...
 

Tony,
Was the REVERSE not working before you flushed the transmission?
IMHO, your lack of a REVERSE has nothing to do with the vacuum system!
With your hand vacuum pump you can test your IP/Engine Shut-Down device that is located on the rear of the IP, between the IP and the oil filter. You should be able to very easily shut off the enigne by connecting the hand pump to the port on top of the IP's Shut-Down "Box" and pumping once or twice. IF you canNOT get the engine to shut down, then either someone installed the IP Shut-Down Box incorrectly or the diaphragm has ruptured. You will readily know if the diagphragm is leaking for you will find that you have been sucking engine oil out of the box's vacuum port! IF you end up replacing your Shut-Down Box, be sure you have the "hook" properly engaged inside the IP or you could cause a run-away incident and destroy your engine!
Report back with your findings BEFORE you try to replace the IP/Engine Shut-Down "Box".
Regards,