transmission rebuild question

Hello everyone, My name is CJ and I have a question regarding what seems to be an inevitable transmission rebuild for a 1981 300TD (the station wagon).
Diesel. Unfortunately, I just bought this car last week. It appears to be a well cared for car - regular oil changes, attending to minor problems and the like. It had both an engine rebuild (by a mercedes dealership - I don't know if this is good or bad) AND a transmission rebuild about 150,000 miles ago - I have the receipt (388,000 total mileage). I believe the engine is in good shape, but a week into it I find the transmission slipping. This is heartbreaking for me, but what can you do, right? Through local word of mouth I am led to believe the couple who sold it to me were aware of this and were not honest with me about it. It appears to have been adjusted to compensate for the slippage. When I bought it ( and for the last week) it was shifting fine. Maybe too smoothly? Hard for me to say, I am new to both Mercedes and automatic transmissions, having always driven a 1979 4-speed Volkswagon van. But I really wanted to share in this grease car movement, so here I am. In any event, I have read a few postings about transmission rebuilds and have a couple of questions if anyone has the time or interest to share their wisdom. First, I am under the impression that you can get a true German made Mercedes transmission or the American made counterpart. And that the German made is of better quality ( and more expensive, I would assume). Is this the case? Or are the German transmissions no longer available? Secondly, I have always been a standard/manual transmission person. This is the first automatic I have ever owned. (also the most expensive car I have ever bought - too bad for me). If I am going to have to come up with the money to fix this problem, is it possible to put in a standard/manual transmission instead of the automatic? I had initially hoped to find a station wagon with a manual transmission but was told it was next to impossible to find this in the U.S. If anyone has any advice on this topic I would so greatly appreciate it. I don't really know what else to do. Best regards to all - CJ
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1) Change the trans fluid and filter, don't forget to drain the torque convertor. This alone may fix it.
2) A common source of slippage is too much vacuum getting past the vacuum modulator; the amount of slipage is controlled by this vacuum, there should be enouhg to make it comfortable but not enough to make it mess up shifts badly.
Unplug the vacuum that goes to the tranny. If it still slips when shifting you're screwed and need a new tranny (assuming 1 has been done). If however if shift HARD but works ok then you need to adjust your vacuum going to the tranny and the tranny is ok.

Never heard this.

Converting an auto to a manny tranny is fairly nontrivial.
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Richard also has excellent info on tranny diagnostic too at his website. http://www.mbz.org .
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"Richard Sexton" wrote:

Good luck finding a flywheel!!!
The 240D came as either auto or manual. You cannot swap transmissions because the crankshafts are totally different [part numbers too] and you cannot bolt the 240D manual flywheel on a 240D automatic crankshaft.
I have no idea as to what crankshaft is used in a 617 turbodiesel engine with a manual trans as I have never seen one in the USA. In the 27 years I have been working as a tech at a MB only dealership, I have seen a couple of Euro 300D's with manual transmissions but they have all been naturally aspirated.
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Apparanly there isn't one, that is, there has never been a manny tranny 5 cyl turbo. Legend has it MB trued using the 6.4 tranny and kept blowing it up. A few people have tried the swap and in six months, they blow up.
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From:        Richard Sexton - view profile Date:        Tues, Mar 14 2006 7:39 pm Email:          snipped-for-privacy@news.vrx.net (Richard Sexton) Groups:         alt.auto.mercedes Not yet rated Rating: show options
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Apparanly there isn't one, that is, there has never been a manny tranny 5 cyl turbo. Legend has it MB trued using the 6.4 tranny and kept blowing it up. A few people have tried the swap and in six months, they blow up.
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I've been running my 4 speed with the 300 turbo for about 4 years. No
tranny problems of any kind. I'm currently out of service with it, but
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Good heavens. That's the first I'd heard of this working, everybody elses blew up. Congrats.

Where are you?
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The mechanic who did the swap said it shouldn't be a problem. While I have since had some major issues with him, I guess he was right about that. I think I have somewhere around 15K miles on it since the swap. YMMV, but I've been very happy with it. Just wish I had a 5 speed <G>

Idaho
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Thank you Richard. I will try your test of unplugging the vacuum. Many thanks for the info. -CJ
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Always, always first try the simple things - there's always time later for the complicated and expensive.
How do you KNOW the transmission is slipping?
These boxes start off in 2nd gear by default and that makes the car a slug - so you may think it's slipping.
Try this: At a DEAD stop shift into L. Start off - that's 1st gear. Upshift to S and IMMEDIATELY BACK to L to hold 2nd gear.
Then shift to S for 3rd and D for 4th.
Do you still believe it's slipping??
The smoothness or harshness of the shifts is controlled by a vacuum valve on the throttle and a modulator on the transmission. The more the throttle is opened the LESS vacuum to the transmission and firmer the shift - conversely the less the throttle is opened the MORE vacuum to the transmission and the smoother the shift will be. That said, don't expect this old hydraulic box to shift like an electronically controlled box on a 2006 model - it won't, for it never did.
Since you're new to this car you should know its maintenance schedule. Engine oil & filter change at 5K miles, valve adjustment at 15K miles and air, fuel filters and transmission fluid and filter at 30K miles. Repair parts are widely available from second sources like www.thebenzbin.com, www.performanceproducts.com, and www.autohausaz.com, etc.
I've owned a diesel since 1980 and don't understand the fascination of biodiesel but here's a site: http://www.biodiesel.org
The more care you give this old car the more service it will return to you.
Good luck with it!
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Many thanks for the advice. I will try the shifting test when I get home this eve. What you wrote makes sense . I thank you also for the maintenance advice - I actually just had the valves adjusted as I noticed it was slower to start on a couple of our colder mornings. The mechanic I took it to said the valves were too tight and adjusted them. He actually told me he overcompensated and made them a little looser than they should be so they would "settle" into the right spot. I don't know what I think if this. All I know is since I have gotten the car back from him it seems to run much rougher and something around the air filter housing seems loose and is rattling. Maybe not the best mechanic, although he was recommended by word of mouth. If you have any thoughts on this feel free to write me back. I hope I don't offend you with the biodiesel application. They are so lovely, these Mercedes; I would never want to do anything that would ruin a car's integrity. It is such a simple conversion, though, and it still allows me to run straight diesel in the car if I so choose. I half believe that it is either the thickness of the vegetable oil on a cold morning that is impeding the start or maybe worn out glow plugs. I am going to drain the tank of the SVOil and put real diesel in to see how the car runs on that. Just as a note of interest, I read somewhere that the person who developed the first diesel engine designed it to run on peanut oil. Again, many thanks and all the best to you -CJ
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There's nothing wrong with running an engine on veg. oil. You should know however, that 100% biodiesel (from the pump) will dissolve old fuel deposits in the fuel system and carry same to the fuel filters, 20% Biod. apparently is free of that sin.
A burned out glow plug will still allow the engine to start (on the other 4 cylinders) but cause an initial misfire for the first 10 seconds or so. You should know that there's an 80 amp fusible link under the glow plug relay's cover (on left fender); these cost only about $1 so carry a spare fusible link for without it there are no glow plugs and the motor won't start except in warm weather.
A valve adjustment ought to make the engine idle better, not worse. Valve adjustment is something you can do if in doubt.
Rattling from under the air cleaner may be due to a broken broken rubber mount or a broken support bracket. Try to lift the air cleaner, if it lifts something needs attention.
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Yes, I have also heard that about new veg oil vs. used veg oil. The people who did the conversion on the car had advised to run a tank or two of NEW veg oil through the engine first, watching the filter for debris let loose by the oil. If all seemed O.K. ( not too much sediment coming out), then they suggested running a couple of tanks of waste veg oil through - again keeping a close eye on the filter. They recommened this course of action because the waste veg oil loosens the debris in the engine at a much greater rate than even the new veg oil (or so I'm told). I guess they want you to "break it in" slowly. I was unaware that true biodiesel had a similar effect, altough logic would lead one to that assumption based in the straight veg oil information.
By the way, thanks again for the invaluable tip regarding the fusible link & the glow plugs. I am hoping that changing out glow plugs should be no more difficult than switching out spark plugs. Hope I am correct!
As a side note, I think the valve adjustment was fine. I just put some true diesel in the tank and I think it was just settling in to the various adjustments & changes. Interestly enough the engine fired up so much more quickly this morning with the regular diesel. I do not have the dual tank conversion so I think it is just that much harder for the engine when the veg oil is cold and thick. Best regards, CJ
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I am hoping that changing out glow plugs should be no more difficult than switching out spark plugs.
Very similar, be sure to buy either Beru or Bosch GPs.
And, use a 1/4" metal drill to cut the carbon from the cavity so the new GP goes in easily. Just twirl it in the hole using your fingers - that's sufficient to do it.
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Yup, that's the right thing to do. as they build up a little carbon they now sit exaclty on spec. This trick saves you a few months before your next one. ALWAYS get them adjusted in the fall (if you want to start all winter)

The air filter bracket lasts 2 months then breaks. They ALL do. What has workd for me is to add an addional mount - a small block of rubber between the uh, um, don't remember, but it's beteen the air filter bracket and the motor. Mine's lasted 4 years this way now, a new indoor record apparanly.

Los of poeple run waste vegetable oil or biodiesel in these things.
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