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'80 300SD (W116), '81 300D, '89 560SL, '01 E320
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140 Posts
Discussion Starter #1
Hi guys...just bought a 1981 300D with over 250k miles (photos below). The car is pretty clean and runs great. There are the expected flaws in the paint, interior, etc. But the one big issue right now for me is that the transmission slips on acceleration. The fluid was very low (while running, it was not even showing on the dipstick but when turned off, it came almost to the lower limit mark on the dipstick) but we filled it with dextron iii (possibly a bit too high but only a tad over the upper limit).

After filling, we still have the slipping. On relatively hard acceleration (i.e. more than 50% throttle), the car sounds like it revs too high and slips, imagine depressing the clutch pedal on a manual while accelerating. If I release the throttle and then press again not too hard, everything is fine. It doesn't seem to slip once at speed.

Here are some photos of the car (anyone know why there is foil on the hose in the hood?):







 

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83 300D Turbo
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219 Posts
Congrats on the car. I would say that searching will be you best friend. There are thousands of posts on transmission issues. First you have to understand that the heart of the car is the vacuum system, if this is not working correctly no amount of changes to your transmission will fix the problem. Read up on vacuum troubleshooting, once you know and have tested your vacuum and it's all in spec, you can start to look at the other common issues. There are several great posts these transmissions, just do some searching here and in google.
 

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1981 300D with a funny tranny
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965 Posts
Hello,

Congratulations for the car!!
I had some tranny problems and I spent hours looking around in threads here and all over the web. I spent more than 500 dollars changing parts that didn't need to be changed. Nothing worked. I'm grateful for all the advice I got from everybody though.

Finally, I bought a Diagnose kit from mercedes source and I fixed the problem with just cleaning the engine with a diesel purge and replacing some vacuum rubber connections. Very cheap.

My advice, so you don't waste any money and get educated, is to buy the diagnostic kit from MS. You will learn so much, and will be able to troubleshoot and repair so many things that will save you hundreds if not thousands of dollars. It also includes a lot of info to make your engine run at its full potential.

Before playing mechanic, make sure you are going to be fixing and not making worse the problem. Learn first, order and read their manual it comes with vacuum gauges and some tools to diagnose but it does not include a hand vacuum pump (a very important and a must have if you own a w123) order that from them too. Its the best deal beacuse they give you a bunch of vacuum fittings and hose with it.

Welcome to the adventure, be wise and patient, this is the link that saved me from selling my car for cheap after everybody told me that the tranny was shot.

123 126 Diesel Transmission Ultimate Diagnostic and Tuning Kit | MercedesSource.com

and dont forget to order the hand vacuum pump!

Vacuum Hand Pump Tester and Brake Bleeder | MercedesSource.com

I repeat, don't waste your time and be frustrated. This is my most precious investment after I bought the car.
 

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Premium Member
W-1-2-3 Go!
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16,161 Posts
Search for "slipping" or "flaring" and you'll find tons of threads on where to start looking.

Thanks for the photos, I realized the Bundt hubcaps do work well on the W123!
 

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1981 300D with a funny tranny
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965 Posts
ohhh... and the foil. Somebody's mickey mouse fix, that is an AC pipe so it needs to be insulated from the cam heat.

Get that loose stuff out of there, before it ruins something.

Things you can do for now:

-Change air filter
-Change fuel filters (do a diesel purge if you know how to, MS sells a kit too)
-Add some injection cleaner additive.
-Change oil and oil filter.
-change any leaking fuel hose, specially in the injectors. (bad injection=bad shifting)
-Order the diagnose kit and hand pump tonight! =)
 

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Daily Drive 82 240D 4 speed
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291 Posts
judging by the picture, im afraid to see under that drivers side carpeting. I hope you had checked that.
 

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'80 300SD (W116), '81 300D, '89 560SL, '01 E320
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140 Posts
Discussion Starter #7
What *could* be under the drivers side carpeting?
 

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'80 300SD (W116), '81 300D, '89 560SL, '01 E320
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140 Posts
Discussion Starter #8
Got results from Mechanic on this car

I brought it over for a checkout by our friend the MB mechanic and here's what he says:

*lower control arm bushings need replacement ($90 parts, 4 hours labor, will throw alignment in for free)

*oil cooler lines leaking ($175 for 2 hoses, 2-2.5 hours labor)

*All belts are showing cracks (2 belts are cracking, may as well replace them all. $45 for belts, 1 hour labor)

center carrier bearing and boot is torn, (center support of driveshaft, can knock on driveshaft tunnel. for now, it's just an annoyance, but should be fixed eventually) ($75 for bearing and boot, 2 hours labor)

sump pump on transmission by torque converter is leaking tranny fluid by screen. tranny has to come out to seal leak ($800) eventually it will leak worse. The slipping is most likely caused by bad seals inside. Tranny can not be fixed unless it's removed from car and serviced. Plan for $800 - $1000. Could burn out the tranny if it leaks too much)

cooling system - on top of radiator - coolant is leaking at top tank. not leaving puddles yet but should be fixed before summertime. ($395 for radiator, 1 hour labor)

motor mounts are flat, but not completely, plus tranny mounts are aging. This can wait. ($80 for 2 motor mounts, 2 hours labor)

That's it. This car cost $650. I wonder if it is worth fixing. The transmission part is quite worrisome for me. I do remember that one guy selling another 300D had offered to give me for free a 4-speed transmission he had sitting in his garage. He said he had considered putting it in. I wonder if I can get it from him...no guarantee it'd even work or fit. Should I just get rid of this car?

Thanks!
 

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1984 Mercedes 300D Euro Spec
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462 Posts
I say keep it! Inca red is a rare color only offered from 1979-1981. You'll have a hard time finding another one in that color:thumbsup:
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,446 Posts
Although some have been lucky, 81 transmissions are bad news. Don't put any money into that transmission. Read, read, read. You may be able to sort out some vacuum leaks and get it shifting well again, but if it's worn, then you should consider finding a different transmission. It's a crummy system which uses vacuum for both shift point and shift quality. The newer units have added a bowden cable which controls the shift points (timing), leaving vacuum responsible only for shift quality. Much improved. Much easier to trick into shifting properly.

Keep your eyes peeled for junker turbo models with good engines and transmissions. The turbo engine is a nice upgrade if you wanted to go all the way, but the 82+ transmission with the Bowden cable is a much better unit, and has a lot more available adjustments which you can use to compensate for wear. Chances are you can find a transmission to swap with yours that will run fine for quite a while.

You could also comb junkyards for used transmissions. If it comes down to having a transmission rebuilt, you're much further ahead to have the better transmission rebuilt than to have yours rebuilt.

When looking at junkyards, grab the brackets on top of the valve cover, you'll need them to attach the bowden cable that yours doesn't have.

Not much on these cars are difficult to DIY... you could consider that. If you had an MB mechanic inspect the car for you, hopefully he found everything. If so, get everything fixed, swap in a used trans, and enjoy. It'd be worth it.
 

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1981 300D with a funny tranny
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965 Posts
I brought it over for a checkout by our friend the MB mechanic and here's what he says:

*lower control arm bushings need replacement ($90 parts, 4 hours labor, will throw alignment in for free)

*oil cooler lines leaking ($175 for 2 hoses, 2-2.5 hours labor)

*All belts are showing cracks (2 belts are cracking, may as well replace them all. $45 for belts, 1 hour labor)

center carrier bearing and boot is torn, (center support of driveshaft, can knock on driveshaft tunnel. for now, it's just an annoyance, but should be fixed eventually) ($75 for bearing and boot, 2 hours labor)

sump pump on transmission by torque converter is leaking tranny fluid by screen. tranny has to come out to seal leak ($800) eventually it will leak worse. The slipping is most likely caused by bad seals inside. Tranny can not be fixed unless it's removed from car and serviced. Plan for $800 - $1000. Could burn out the tranny if it leaks too much)

cooling system - on top of radiator - coolant is leaking at top tank. not leaving puddles yet but should be fixed before summertime. ($395 for radiator, 1 hour labor)

motor mounts are flat, but not completely, plus tranny mounts are aging. This can wait. ($80 for 2 motor mounts, 2 hours labor)

That's it. This car cost $650. I wonder if it is worth fixing. The transmission part is quite worrisome for me. I do remember that one guy selling another 300D had offered to give me for free a 4-speed transmission he had sitting in his garage. He said he had considered putting it in. I wonder if I can get it from him...no guarantee it'd even work or fit. Should I just get rid of this car?

Thanks!
Would it be worth to spend $122 to find out what needs to be done yourself and then decide what you want to do?

There will be some reading and understanding. If you are not willing to learn how to work on your car yourself, then you will have to pay that much to keep it. :eek:

I had a worse diagnosis. The total of things to fix it was about 4000.

I repaired it slowly myself for about 500 at the most. :thumbsup:

Although, if I could afford to get it fixed for 4000 I would have done that instead.

Anyways, be patient and read:D

Mercedes Benz Owners Best Source for D.I.Y Repairs, Diagnostics, and Quick Fix / Kit Solutions | MercedesSource.com
 

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2001 Volvo V40
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2,954 Posts
Although some have been lucky, 81 transmissions are bad news. Don't put any money into that transmission. Read, read, read. You may be able to sort out some vacuum leaks and get it shifting well again, but if it's worn, then you should consider finding a different transmission. It's a crummy system which uses vacuum for both shift point and shift quality. The newer units have added a bowden cable which controls the shift points (timing), leaving vacuum responsible only for shift quality. Much improved. Much easier to trick into shifting properly.
Up to a point, Lord Copper. If you've got the shift points correctly (they are in the FSM) on the vacuum-only transmission, you know that the modulation pressure (that controls the shift quality) is OK. With the seperate system, if you want to do it correctly, you have to connect a pressure gauge to the transmission to get the modulation pressure in good order.
 

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Registered
1981 300D with a funny tranny
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965 Posts
Up to a point, Lord Copper. If you've got the shift points correctly (they are in the FSM) on the vacuum-only transmission, you know that the modulation pressure (that controls the shift quality) is OK. With the seperate system, if you want to do it correctly, you have to connect a pressure gauge to the transmission to get the modulation pressure in good order.
I agree, and read read read!:thumbsup:
 

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Registered
'80 300SD (W116), '81 300D, '89 560SL, '01 E320
Joined
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140 Posts
Discussion Starter #14
Although some have been lucky, 81 transmissions are bad news. Don't put any money into that transmission. Read, read, read. You may be able to sort out some vacuum leaks and get it shifting well again, but if it's worn, then you should consider finding a different transmission. It's a crummy system which uses vacuum for both shift point and shift quality. The newer units have added a bowden cable which controls the shift points (timing), leaving vacuum responsible only for shift quality. Much improved. Much easier to trick into shifting properly.

Keep your eyes peeled for junker turbo models with good engines and transmissions. The turbo engine is a nice upgrade if you wanted to go all the way, but the 82+ transmission with the Bowden cable is a much better unit, and has a lot more available adjustments which you can use to compensate for wear. Chances are you can find a transmission to swap with yours that will run fine for quite a while.

You could also comb junkyards for used transmissions. If it comes down to having a transmission rebuilt, you're much further ahead to have the better transmission rebuilt than to have yours rebuilt.

When looking at junkyards, grab the brackets on top of the valve cover, you'll need them to attach the bowden cable that yours doesn't have.

Not much on these cars are difficult to DIY... you could consider that. If you had an MB mechanic inspect the car for you, hopefully he found everything. If so, get everything fixed, swap in a used trans, and enjoy. It'd be worth it.
Wow, that's great advice. I am just getting to this now. First, I am going to try new filter and fluid, as many people have said that often helps, especially if it hasn't been changed in a long time (which I suspect is the case). While I am having that done, I was planning to replace the K-1 spring/piston (I found the kit for about $7 wholesale).

If that doesn't work...I guess I do have to find another transmission. I have been looking at two junkyard cars -- one is an 85 300TD, and one is a slightly older (I think 80) 300 Turbo Diesel wagon.

Thanks everyone for all the comments and suggestions. I'll update after this transmission service.
 
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