Bad Transmission

[Deja Stu]

I'm looking for input from those of you who have had a tranny "transplant". Let's face it, if money was no problem, I'd just drop it off at the dealers, and let them have at it.( I was quoted $3711 to replace the transmission in my 1985 300 TDT) I hear a Mercedes exchange program transmission for my car runs about $2000. no doubt reliable, a sure thing. I see a "mail order" rebuilt transmission out of Indiana, in this months Hemmings motor news for $1195. How much shipping cost on a transsmission? it has to be costly, making the drive to pick it up in person is an option......dropping the transmission out of the car will be no problem, I've done this on other cars, and I have no problem with doing the mechanical work myself. A third option sounds best to me,what do you think?A nearby independant shop will do the complete job for around $1450. This is his price with the transmission still in the car. He sounds knowledgable, and reports that he prefers to do the whole job, he wants to "set it up" after the rebuild. What do you think:confused: Stu

[Tom Hanson]

If you found a reliable independent shop to do this job for $1450 then go for it. make sure they have an iron-clad guarantee. This sounds about right for a "routine" rebuild. Insist on Genuine MB parts !!!

[VLayton]

I'd say his request is reasonable. Price isn't bad either, I hope it works out. Automatic transmission is a subject I feel I'll never know, and I have learned many MB intricacies when doing repairs that aren't always obvious or thought of. I hope your guy knows what they are if there are any regarding this one. Any 1st time repair/shop/mechanic is somewhat of a gamble, but if you don't try, you won't find "service gold"

Best of luck, keep us posted

Vince

[familydieseldr]

I went with the factory rebuilt option for a new transmission in our 1983 300TD. (I just did not want to take and chances with it)
I took out the old transmission so I could take it with me to exchange it as a core when I made the trip to the MB dealer to pick up the new transmission.
My local MB dealer gives a few percent discount to MBNA club members, that helped reduce the cost a little.
While I had the trans out, I put in a new rear mount.
I also bought a new torque converter. I found out later that it was not needed, the old converter is still working fine at 330,000 miles.
The only hard part was getting to some of the bell housing and starter bolts, and I needed the "thin wrenches" to get the drive shaft off.
Frank

[Deja Stu]

thanks Frank, any trouble with setting it up after you got it installed? I guess what I mean to ask is, was it just a bolt in swap? It shifted at the correct times and all that jazz? Is there a procedure for setting the modulator pressure that needs to be done? Stu

[Robby Ackerman]

Check out this article re adjusting the transmission:

http://www.mbz.org/resources/articles/trans/

[Robby Ackerman]

Here are some transmission notes I had in my file that were written by Dr. Marshall Booth.

Date: Sat, 24 Feb 2001 17:43:58 -0500
From: Marshall Booth <mbooth+@pitt.edu>
Subject: Re: [DIESEL] Early shifting

Kevin, NO the transmission is NOT vacuum shifted! The transmission shifts when the ATF pressure reaches some pressure level. The precise pressure to trigger a shift is a function of the position of the control rod (old) or cable (since the mid/late '70s) that is controlled by the linkage to the accelerator. Vacuum ONLY changes the force or firmness of the shifts and low/no vacuum equates to a firm/harsh shift while high vacuum gives a soft shift. If the transmission is shifted prematurely (or
the shift is delayed 'til well past the appropriate shift point) the
most likely culprit is improper adjustment of the cable or failure of
the regulator that the cable operates.

There ARE conditions that will manifest themselves as improper shifting points when the linkage IS properly adjusted, but the engine is not working correctly (as when the banjo fitting or switch over valve are clogged) but these apparent shift anomalies are the result of having to push the pedal further to obtain a level of power and the linkage is PROPERLY adjusted to signal at the design level of power with the pedal in that position - not the reduced power that inactivation of the ALDA
circuitry imposes. (Was that a sentance? Did anybody understand it?)

This particular malfunction results in changes in both shift point AND firmness, but both are corrected when the ALDA pressure signal is restored and the engine runs PROPERLY again.


Dwayne, If the cable is incorrectly adjusted, the shift points will NOT coincide with the vacuum signals which control the firmness of the shifts. Inproperly adjusting the cable in one direction will make the transmission shift earlier cause the shifts to be early and I believe and a bit soft while improper adustment in the other direction will cause the shifts to be late and possibly harsh. I expect that you will do little damage to either the transmission or the engine running with this improperly adjusted for a while (providing engine/tranmission wear is not at the extreme limits) but it would be desireable that the adjustment be correctly set. I have NOT adjusted a W123 turbo in many years so will leave it to someone that has done it at least THIS decade to supply the details, but it's EASY and very straightforward! Do NOT try to "tune" the way the car runs with this adjustment - simply make
according to the "book" and if things are still WRONG, look for another cause (like the fingers that operate the vacuum supply to the modulator and EGR are worn or out of calibration - or the banjo fitting/switchover valve is clogged) and repair/fix that!

That softness would lead me to speculate that pressure is a bit low and/or the clutch related to the 3/4 shift (K-2) is glazed or worn - now lets see if that REALLY makes sense. Well according to the ASTG manual that's their diagnosis too - at least for starters. They suggest check and adjusting modulating pressure and then examining and renewing or reconditioning the inner plate of K-2 OR replacing the shift valve housing!

Marshall

[familydieseldr]

Deja,
I was pretty simple, I think the MB rebuilt did not come with a modulator or the mechanical/electrical shift linkage module, etc. the MB usit was just the basic transmission, so I moved all the external bits from the old one to the new one.
I just had to adjust the shift cable, done.
Frank

[Deja Stu]

Thanks for the input guys, I have decided to let the shop handle the rebuild of my transmission. After visiting the shop a second time, talking with the owner, and getting a look at what a clean, orginized shop he runs, I feel I can't go wrong for the estimate of $1350. I'll let you know in a few weeks how it went. Stu

[Deja Stu]

Well thinking I was going to get out of there for $1350 was pretty foolish on my part.You NEVER know what a rebuild will cost untill you open her up and see what you are dealing with. Total cost $2306. Still not bad, Let me tell you how it went. First off let me say I had three other jobs included in this rebuild. First we found my drive shaft carrier bearing to have seperated from it's rubber mount, so it was replaced,I had purchased in advance a rear transmission mount, good thing, because the old one was shot.No installation charge there.They also did a lower oil pan gasket, and a valve cover gasket, plus 6 qts oil.My tranny needed some internal goodies, so this added to the price. This shop gives a 12 month, 12,000 mile warrantee, and I think thats pretty good for a car with 212K My transmission guy said he wished he only had to warranty Mercedes Benz transmissions, because 12,000 miles on them is no sweat, it's the others he rebuilds that he has to worry about. He was amazed that I "drove in" with my transmission in the shape it was. A testimonial to the Mercedes Benz. They never quit, and now mine has a new life. I'm very happy. See you on the road! Stu

[Robby Ackerman]

Interesting. Thanks for the update.

[VLayton]

Fabulous. Does it shift and engage like "glass"? (I've never had a new or rebuilt unit, but I've tuned some to be quite nice)

Sounds like a good deal, that's a lot of work. Now I'd check the timing chain for replacement, and with maintenance your drivetrain should get you the the big 500, if your odometer keeps working! (Zatt ist a little joke, yah?)

I finished a timing chain Monday, at 276,000+ miles, wow, what a difference! She deserved it.

Later, all

Vince

[Deja Stu]

It shifts fine. It's such a big difference. I really have nothing to compare it to. It is smoother when it warms up a bit. I'll let you know in 6 months hows it doing. Now whats this about a timing chain? What are the classic symptoms of a worn timing chain? Is this a job that can be done by the amateur? Stu

[VLayton]

The timing chain is a big part of getting into that 500k+ range.
The w123 diesels use a heavy duty double row timing chain than holds up a long time, sometimes over 300k for a well maintained example. However, lately I've been driving a poor example of maintenance that wants one at only 140k. Most modern engines have a belt, which does no damage if it breaks, with recommended replacement of 30 to 90k. With these, one can play it more by ear. 616, 617, and 617a engines require a valve lash check and adjustment every 15,000 (or so) miles. This is when I inspect the timing chain for looseness. You should not be able to lift the chain up off the cam sprocket at all. If I can pull a link up even half a millimeter I'd say do it. With new chain I'd also replace the tensioner, tensioner slide rail, and the guide rail. The replacement of the lower inner and outer rails requires dissassembly of the engine, so I skip these for a in-car chain replacement. For good measures, one can also replace the cam sprocket, but the crank gear again requires engine dissassembly.

When the chain gets sloppy you should be able to hear it. Occasional odd clinks and clanks at rpm are also an audio giveaway.


A good system, yes, I prefer it to a 30k rubber belt, but chain wear must be caught, because if it goes arwy, it's time to rebuild the engine. Doing it yourself is subject to debate, and requires special tools, but I won't be the one to tell you "you can't"
It is intense, and must be right! I think a good price for chain, tensioner, tensioner rail and guide rail and cam sprocket is about
$775, installed with new coolant, and why not add all new belts for another $50-60 (if they'll give you a break).

I hope this was enlightening and helps you keep up on your car's life.

Regards,

-Vince

[familydieseldr]

Hi,
We changed the timing chains on our 300TD and 300SD at about 200k "just because".
It was actually easy except for one part.
I ground the head off the pin at the top of the sprocket and tapped it out.
Then I used the pin to connect the new chain to the old chain, rotated the crankshaft by hand while my wife guided the new chain in & old chain out.

The hard part was swaging the pin end in place.
I tried using a motorcycle chain breaker/pin swager,
but it did not do a good job, so plan "B" was to TIG tack weld the pins in place.

Now the 300TD has 130,000 on the new chain, the 300SD had 70,000 on it's new chain. Well, I guess the chains aren't actually new any more......

Frank

[Deja Stu]

2/1/05 Just checking in to let you know my tranny is doing great. No problems. I'm very happy with my independant shop rebuild.