Transmission compatibility questions - PeachParts Mercedes-Benz Forum

NCfriend · #1 04-26-2011, 10:33 PM

Would some of the more experienced members please set me straight:

What models could I use a 1984 300D turbo 5 cylinder transmission with?

What models would accept a 1979 300SD turbo 5cyl transmission?

What models can use a 1977 300D non-turbo 5cyl transmission?

And finally, would any of the above trans work in a 1986 300SD?

I should probably know the different part numbers, but I am not very good at finding those on different year transmissions. I believe options are increased if you are willing to change yokes, drive trains, and/or rear differentials to match????

All your advice is greatly appreciated!
If you need any of them please message me. All drivable now.

barry123400 · #2 04-26-2011, 11:09 PM

I can only answer a couple of your questions. The 77 300d non turbo transmission is not the best ideal to use in a turbo model. It is less robust. Plus there are differences in control configuarations I think.

No 123 transmission bolts up to a 1986 engine either. The starter is on the wrong side.

Stretch · #3 04-27-2011, 03:13 AM

I've asked a similar question and I've got some answers for you that might help

Just dreaming - 300D automatic gearbox replacements?

I wouldn't go backwards in time - if you see what I mean - don't downgrade to an older transmission.

I think that if you change transmission adapters / get transmission adapters custom made, change "tail cone" sections on the end of transmissions, change bell housing sections on the front of transmissions, get custom made propshafts, hook up bowden cable assemblies if needed etc etc etc almost anything is possible - but it will be expensive.

In short this sort of work can be quite involved and expensive - you need to be keen to want to do it. There seem to be very few plug and play solutions... the easiest option is to stick with what you've got. But don't let me quench the desire to fit in a VW DSG or something like that (I would if I had the cash and the time!).

NCfriend · #4 04-27-2011, 11:25 PM

Thanks for the input guys. The thread within a thread from Army helped a bit. Obviously I need to get some numbers off these donor transmissions so I don't sound like such a novice boob!

Till then, let me narrow the question down a bit.
Is it too difficult of a job for:

A 1984 300D turbo trans working with any years of 300SD?

Lastly, is the trans from a 1979 300SD good for any other year or model?

Thanks for humoring me!

vstech · #5 04-27-2011, 11:34 PM

Quote:

Originally Posted by NCfriend

Thanks for the input guys. The thread within a thread from Army helped a bit. Obviously I need to get some numbers off these donor transmissions so I don't sound like such a novice boob!
Till then, let me narrow the question down a bit.
Is it too difficult of a job for:

An early 1977 300D trans work with a 240D auto?
should be the same, or close enough.

Or a 1984 300D turbo trans work with any years of 300SD?
81 300TD is exactly the same transmission... but rare.
81-85 SD's should accept the 84D transmission, if you swap the speedo sender, and gear/tail piece.

Lastly, is the trans from a 1979 300SD good for anyone else?
should fit in an 80SD... different in anything else I think...

Thanks for humoring me!

Skippy · #6 04-28-2011, 06:04 PM

That '79 SD transmission should also work in a '78 SD.

Edit: 1600th post.

ROLLGUY · #7 05-08-2011, 04:27 PM

Quote:

Originally Posted by NCfriend

A 1984 300D turbo trans working with any years of 300SD?

I just put an '85 300D trans in a '81 300SD. Three problems: (1) The neutral safety switch and reverse light wiring connectors are different = easy fix by soldering the connector from a donor harness that fits the D trans. (2) The speedometer on the SD trans is electric, and the D trans is cable. (3) The shifter arm on the D trans is shorter, making the shifter gates not line up. The shifter I could probably live with and/or easily fix, but I do need a speedometer. I thought about putting a cable speedometer from a 300D in the SD, but then I would need to drill a hole in the firewall, and that is not an option. The D trans was available, and I did not know about the differences until I had the trans installed. I thought I could change the tail housing, but they are completely different internally, and bolt pattern different on the housing.
Anyone have any ideas how to make the electric speedometer work with the cable trans?

NCfriend · #8 02-16-2012, 08:24 PM

So, I am refreshing this thread with this new question:

Will my newly acquired 1984 turbo 300td WAGON transmission work on earlier 300D sedans?
(specifically bolt onto an '82 turbo sedan without any mods)
I need to add that this donor trans may be more like an 1985 as "It has the 'blue flying saucer' in the vacuum system to improve shifts..."

I will try to get the actual part number off the transmission as soon as we dry out here

Is there any reference section or earlier thread that covers ALL the w123 transmissions and cross compatibility (or necessary modifications) between different years?
Sure would be nice from someone that knew the answers...

ROLLGUY · #9 02-17-2012, 12:53 AM

1982 & newer 300D trans is 722.4XX. The D, CD, & TD used the same trans from 1982-1985. 1986 & newer has the starter on the other side. 300SD trans (722.3XX) is similar, but has electric speedo. 1981 was vacuum only (no mechanical kick down) on all but the SD, and 1980 & earlier (722.1XX) had a kick down rod (not cable).

mach4 · #10 02-17-2012, 03:07 AM

Quote:

Originally Posted by ROLLGUY

Anyone have any ideas how to make the electric speedometer work with the cable trans?

Wow, I had no idea you've been working on this issue since May '11 Hang in there we're really close.

rs899 · #11 02-17-2012, 07:00 AM

Quote:

1982 & newer 300D trans is 722.4XX. The D, CD, & TD used the same trans from 1982-1985.

I respectfully dispute this info. The 82-84 trans is 722.315 (the 81 TD is also 722.3xx, I think). The 85 is 722.4xx

Stretch · #12 02-17-2012, 07:49 AM

Quote:

Originally Posted by NCfriend

...
Is there any reference section or earlier thread that covers ALL the w123 transmissions and cross compatibility (or necessary modifications) between different years?
Sure would be nice from someone that knew the answers...

I started this thread a while back

FSM + EPC data => Chassis / model / transmission / drive train information

I posted it in DD but it got quickly relegated to "General Information" where nobody will read it! I can understand why - it is my own fault - I should have used the key words / phrases "Diesel" and "my 300D" in abundance!

If any of you experts can add to the thread that would be great.

ROLLGUY · #13 02-17-2012, 12:00 PM

Quote:

Originally Posted by rs899

I respectfully dispute this info. The 82-84 trans is 722.315 (the 81 TD is also 722.3xx, I think). The 85 is 722.4xx

After looking back at the EPC, I stand corrected. However, with the exception of SD (electric speedo),all D, CD, TD trans's from '82-'85 should be interchangeable?
I think that is basically the OP's question.

NCfriend · #14 02-17-2012, 12:23 PM

Quote:

Originally Posted by ROLLGUY

After looking back at the EPC, I stand corrected. However, with the exception of SD (electric speedo),all D, CD, TD trans's from '82-'85 should be interchangeable?
I think that is basically the OP's question.

That is my most recent quadry and if the above holds true in practice, we are golden!

My late edit was to see:
if this end of '84 production year wagon, happens to have "The 85 is 722.4xx transmission", will it cause any difficulty to swap into an earlier model sedan (back to 1982)?

ROLLGUY · #15 02-17-2012, 12:54 PM

Quote:

Originally Posted by NCfriend

That is my most recent quadry and if the above holds true in practice, we are golden!

My late edit was to see:
if this end of '84 production year wagon, happens to have "The 85 is 722.4xx transmission", will it cause any difficulty to swap into an earlier model sedan (back to 1982)?

Although there may be differences, I am reasonably sure the two are compatible. I know you probably don't want to pull both of them and compare them side by side, but that would be the best way to know for sure.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode