I just got a 1981 300SD 5 cylinder automatic transmission. Well I took it out for it's first drive after having it dollied to my house. It seemed to be shifting hard like you could feel it in the car. I thought this was normal. However after about 100 mile trip come cruising down a hill coasting into town, stop light up ahead about 100 yards so I gently stepped on the gas and it revs and no gear. Fortunately I was able to coast into a nearby gas station. I checked the tranny fluid it was fine, no drips, burnt smell or discoloration. Clean under the car - no leaks.

So thought it may have heated up sat for two hours and tried it a few times in between - nothing no gears just park. When I shifted through the gear shift it felt like there was nothing there. When I put it in a gear and pressed the gas peddle the speedo jumped like it was in gear but the car does not move.

Sometimes when I put it in gear heard a low growl but not every time. It did move the speedo everytime though. Checked the vacuum lines and wiring no apparent problem there.

So had to have it towed home - $500.00 touch for that.

Now I am at a loss. I came home did a more indepth of the vacuume and wiring. So decided to pull the tranny to look at the torque converter and rear end. All looks good. Torque converter is good, the rear end nice and tight nothing out of place. What is the problem that is my question. Is the tranny screwed?

 

For others do not ignore extremely hard shifting.
Also if you drive old Cars it is a good idea to be a member of one of the Auto Clubs that has at least some free towing. Also some Insurance Companies are also offering that.

You said you had it dollied to your house and the Rear Wheels were on the road: I don't know for sure but I believe I read that the older Transmissions do not have the 2nd pump; and if you tow it and the driveshaft is spinning there is no pump turning to lube your transmission.

If it where mine and the Transmission had been still on the Car I would have tried Changing the Filter First.
I had a problem where my Transmission was not going into first gear. I changed the Filter and the problem went away. That was a year ago.

I am not sure what transmission number is on your car but ASTG sells Thin Transmission Books for around $27 and shipping they still have books for transmission models 722.2-4 and up but no longer sell the 722.2 and below manuals.
You can Find them on eBay by searching Mercedes Transmission Repair manual.

I applaud your willingness to act and pull the Transmission but my thought is that by doing so you now can not trouble shoot it with out taking it apart and inspecting the parts.

Putting a Test Gauge on might have told you if the Pump had gone bad or?

 

I didn't say the rear wheels were on the road! I don't know where you see that... When the car was dollied the drive wheels were on the dolly because the car is rear wheel drive. So having it dollied is not why it's screwed up.

I admit it may have been premature to pull the transmission but everyone was telling me it was the torque converter.

When I checked the filter for the tranny it was like new.

Look at the pics... does everything look good to you? The transmission has the number 12v=087A3.82

The vacuume lines were secure, everything is smooth and nice.

 

Sorry My mistake concerning the "wheels on the Road" comment.

On my Transmission the Number is on the Passanger side; When on the Car it is hard to see due to the Exhaust Pipe.

Unfortunately the Transmission is not one of the items on the Car that there is a lot of info available on.
I have never had mine apart and only several People on the various forums have gone completaly inside. Some have changed the Spring Packs or Pistons (that sometimes crack).

Most simply find another used Transmission.

The ATSG book is not very detailed and the ones that are still available may not be for you trans model.

There was a guy on eBay who sold his homemade Transmission Rebuild Video but I have read that the lighting is not so good on it.

While the various forums have some bits of info there is to my knowlege no step by step type instructions for taking apart, inspeckon and assembly for the whole trans mission on any of the Forums that I have found.

When I looked in the ATSG Trans Manual for my model there was no specific comment for the transmission dieing. Only the symptoms for a transmission that was not running rignt.

This is a site that has an article on Transmissions concerning the Adjustment of the Vacuum and the Transmission Modulator.
http://www.continentalimports.com/ser_ic20242.html

 

When I went to take the drive shaft off I noticed there was a nut rattling around in there. So I pulled the drive shaft out of the car and unbolted the yoke from the drive shaft I realized it screws onto the end of the transmission output shaft so then I thought this MAY be the reason the tranny was "slipping" because IF the shaft slipped off far enough there would be "no connection" to the rear end making it seem like the tranny was slipping... but I guess I won't know until I put it back together ... "eyes rolling" but now that I have it out and it's soooooooo much work to R&R it... I think it's probably a good idea to check them out to make sure they ARE all right ... anyone know how to diagnose a torque converter...

I have a picture above of the torque converter above.

****If the pump failed in the transmission would this cause this efffect. However keep in mind that as I step on the gas every single time the speedo moved as if the car was in gear. But when I shifted from forward to reverse no clunk or grind like it was going into gear. However a few times it would grind when going from park to another gear. No sensation fo going into gear it's like there was nothing there no resistance... Could it be the vacuume module. I felt vacuume the doors lock and unlock so there is vacuume and I felt it was good.

 

If it turns out that loose nut is the cause of your trns issue and you still have the Hard shifting; not dealing with that will shorten the life of the trans.

 

I took the torque converter to a tranny shop and he checked it out said it is good, nice condition. When you look at my tranny pics does anything look out of place. There are no metal filings or bits of dirt when I took out the filter it was clean and so was the fluid. If the nut was out of place couldn't it have seemed like it was causing a hard shift?

 

You will just have to get it back together and see.

I have never had any Automatic Trans apart excep to change the Filter or a Seal on one of the drive ends so I am not the best personto answer on that.

 

Do you know someone on here or someone that can look this over and help me? I really can't afford to put a pile of money into this old car. I got it thinking it would be reliable and since it had low miles I wouldn't have to worry about anything major for at least a year or two not the first time out!

 

That was my arguement to my wife when I wanted to buy my '82 300DT. I paid $900 for her and spent about $3k since. And yet I have no complaints because she's fun to work on.