1987 300SDL Tranny, No Reverse - PeachParts Mercedes-Benz Forum

Gregory · #1 01-24-2011, 12:45 PM

I posted last month about my 1987 300SDL and how reverse gear failed. I bought a used transmission off the Dallas craigslist for $400 and shipped it to Idaho for $250. The seller said it was off a wrecked 1987 300SDL and has 170xxx miles.

My indy has just pulled the original out this morning and is now replacing the rear main oil seal to fix that leak before installing the replacement tranny. He said it looks different from the original. I asked him for the numbers:

My original Trans:
on case, drivers side: 126-271 21 01
Lower, near the pan: 126 270 51 01 722 321 02 886062

The replacement trans:
Lower, near the pan: 124 270 00 01 722 317 02 876840

Can anyone advise as to this swap-out, and let me know if this project is a bust? Thanks!

Gregory · #2 01-24-2011, 01:23 PM

Here is a link to the ad in Dallas.

http://dallas.craigslist.org/dal/pts/2115836435.html

The photos show the engine and tranny. The engine is still for sale. He is specifically saying:

"Mercedes Diesel Engine 603 961. 1987 300 SDL. 176k miles came from a wrecked car Complete except turbo."

Is the 1987 300SDL a W126, or is it a W124? What is the difference between the two, and how easy are they to be confused with each other?

winmutt · #3 01-25-2011, 11:34 AM

SDL is a w126. The difference in the tranny's will be the speedo pickup which is electronic on the 126.

Renntag · #4 01-25-2011, 12:48 PM

Quote:

Originally Posted by Gregory

Is the 1987 300SDL a W126, or is it a W124?

As stated above and in your other thread, the "S" class is built on the W126 chassis. That being said, it shares the same motor (OM603) with the W124, move on to your next question:

Quote:

Originally Posted by Gregory

What is the difference between the two, and how easy are they to be confused with each other?

Surely anyone can confuse the two cars if they are not familiar. Prior to discovering an interest in Mercedes, I couldnt tell you an S from an E or a 300 from a 500 with out looking at the trunk badge. It would seem reasonable to assume that your seller may have many more well meaning country boys involved in the process and one hopped out of his dust covered chevrolet and mentioned that it was "one of them SDLs I think..." and thus here we are. Innocent as it may be, you are 650$ deeper into this project.

As I consider parting out my 617 powered 300SD, I asked another local enthusiast if I could use the tranny as a spare for my W123 300TD. I was told, "Yes, but the tail of the trans has to be swapped, as the W126 has an electronic speedo. There is a special tool to do this, my friend has it".

So with that, I imagine a little more research may find you swapping the tail of the trans and using what you have.

Your other option is to continue to search for a trans, sell the one you have, or consider repairing what you have.

Please update us.

For those searching in the future here is W126 info:
http://en.wikipedia.org/wiki/Mercedes-Benz_W126

Gregory · #5 01-25-2011, 03:05 PM

My indy just called and needs more info about the "special tool" to swap the tail pieces.

Would a shop like Aamco have that tool? Can it be swapped without that tool? And where can the tool be gotten from? Thanks

Renntag · #6 01-25-2011, 05:14 PM

I have put in a request for more info.

winmutt · #7 01-25-2011, 05:53 PM

I would say either live without a speed (its not that hard) or find another trans and sell the one you have.

Hit Man X · #8 01-25-2011, 09:32 PM

Quote:

Originally Posted by winmutt

sell the one you have.

Do this and just rebuild the existing one. It can be done for around $1k if you shop around... the 722 is a very basic automatic trans.

If all your forward gears work fine, you can just replace the reverse clutches easily too. This should be within the scope of any competent independent mechanic as it is one of the most common failures in the 722... while it is out, reseal the entire thing.

Renntag · #9 01-26-2011, 10:04 AM

Quote:

Originally Posted by Hit Man X

... the 722 is a very basic automatic trans.
.

How many here have rebuilt their trannies themselves? I have had manual boxes apart and together, but never an auto.

Just curious if this is something I can do myself in the future.

Hit Man X · #10 01-26-2011, 03:39 PM

Quote:

Originally Posted by Renntag

How many here have rebuilt their trannies themselves? I have had manual boxes apart and together, but never an auto.

Just curious if this is something I can do myself in the future.

If you have rebuilt a manual you can rebuild an auto. I have never been in a 722 minus servicing and playing with the valve body, but I have been in a few AODs and a TH350 plus countless others for shift kits. The 722 just has three clutch packs and two bands. It is simple as can be and durable.

Just keep everything surgically clean and pay attention to the orientation of everything. Something backwards or in the wrong place can lock the gear train or cause failure.

There are a few funky tools you want to pick up or if you are handy you can make them. Basically just to compress the clutch drums to R&R the seals within. You could get by without, but that is just halfassing the job and can potentially induce an internal hydraulic leak... not what you want.

I have the ATSG book (not too much help really) plus the factory PDF that is floating around. I believe Sixto sent it to me years back and I just forward it on to help others. It is about 7kb I think, so PM me with your email and I can send it to you.

whunter · #11 01-26-2011, 06:31 PM

Quote:

Originally Posted by Renntag

How many here have rebuilt their trannies themselves? I have had manual boxes apart and together, but never an auto.

Just curious if this is something I can do myself in the future.

Gregory · #12 06-29-2011, 03:50 PM

I just want to update this thread. I recently noticed that since I swapped out the tranny, my fuel mileage has increased about 10%, from 21-24 mpg to 23-27 mpg.

I think the two trannys are geared differently. The 124 is definitely giving better mileage than the 126 tranny did. Can anyone confirm?

Hit Man X · #13 06-29-2011, 06:42 PM

Considering top gear is still 1:1, I would attribute the fuel economy gain to being back on summer fuel versus winter blend. Seeing as how you started this thread in January and are now updating in June.