Are 124 transmission interchangeable? - PeachParts Mercedes-Benz Forum

broken4door · #1 10-04-2009, 01:11 AM

Hello everybody, I am new to Mercedes diesels automobiles and would appreciate some information please. I purchased a 1987 300d with a bad transmission, the car was ran with very little fluid, and what trans fluid came out looked like mud. Are Mercedes W124 transmission interchangeable between 1987 300D and 1989 300e? I have a 722.31702 transmission in my 1987 300d and found a very low mileage wreck 1989 300E with a 722.358 transmission and a 103983 12 156859 engine. An help will be much appreciated, I was miss lead by the person that sold me this vehicle, it drove very well for 2 days then fell apart, the maintenance records receipts that were provide ended up being from another Mercedes, so know I am trying to deal with issue. I am broke and poor, so any information would much be appreciated,

Thank You very much

pawoSD · #2 10-04-2009, 01:49 AM

My guess is that the trans would work fine and would interchange just fine. There is a user here on the forum (bsmuwk) who has a diesel W124 trans in his gasser....and it was working fine for him.

Will_w202 · #3 10-04-2009, 03:18 PM

the overall answer is that the V8 and I6 trans is not interchangeable; just stick with the gas I6 trans and it will fit

bsmuwk · #4 10-04-2009, 03:41 PM

It should work. Just need to swap out the tail ends of the transmissions as the diesel one is larger than the gasser one.

babymog · #5 10-04-2009, 04:04 PM

What is wrong with the transmission, perhaps we can help.

They are interchangeable, but:

The 300E transmissions start in 2nd gear, extremely annoying IMO. If you can find an E320 transmission for the 1st-gear-start, or another '87 300D it would be simpler.

Also, is your torque-converter good? The torque-converter will have a different (higher) stall-speed on the 300E, not a deal-breaker but you will probably lose just a little fuel mileage.

If the valve-body is okay in your 300D, that is another option, use the 300D valve-body in the 300E transmission to retain the 1st-gear start.

If I remember the gearing is also slightly different, but 4th-gear is 1:1 (minus TC losses) on both so you'll be fine there.

Last, I'm not sure where the speedometer ratio is changed for the different diff-ratio, likely in the speedometer but I'm not sure, someone else might know if this swap will affect your speedometer.

bsmuwk · #6 10-04-2009, 04:17 PM

Quote:

Originally Posted by babymog

What is wrong with the transmission, perhaps we can help.

They are interchangeable, but:

The 300E transmissions start in 2nd gear, extremely annoying IMO. If you can find an E320 transmission for the 1st-gear-start, or another '87 300D it would be simpler.

Also, is your torque-converter good? The torque-converter will have a different (higher) stall-speed on the 300E, not a deal-breaker but you will probably lose just a little fuel mileage.

If the valve-body is okay in your 300D, that is another option, use the 300D valve-body in the 300E transmission to retain the 1st-gear start.

If I remember the gearing is also slightly different, but 4th-gear is 1:1 (minus TC losses) on both so you'll be fine there.

Last, I'm not sure where the speedometer ratio is changed for the different diff-ratio, likely in the speedometer but I'm not sure, someone else might know if this swap will affect your speedometer.

The speedometer will be effected when the differential is changed. Changing just the transmissions won't effect the speedometer. From reading his Benzworld post, he's using 225/55 tires so he's off on his speedometer anyway.

pawoSD · #7 10-04-2009, 05:22 PM

Quote:

Originally Posted by babymog

What is wrong with the transmission, perhaps we can help.

They are interchangeable, but:

The 300E transmissions start in 2nd gear, extremely annoying IMO. If you can find an E320 transmission for the 1st-gear-start, or another '87 300D it would be simpler.

Also, is your torque-converter good? The torque-converter will have a different (higher) stall-speed on the 300E, not a deal-breaker but you will probably lose just a little fuel mileage.

If the valve-body is okay in your 300D, that is another option, use the 300D valve-body in the 300E transmission to retain the 1st-gear start.

If I remember the gearing is also slightly different, but 4th-gear is 1:1 (minus TC losses) on both so you'll be fine there.

Last, I'm not sure where the speedometer ratio is changed for the different diff-ratio, likely in the speedometer but I'm not sure, someone else might know if this swap will affect your speedometer.

The torque converter on the 300E is a higher stall speed? What is it on the diesels? Its only 1600rpm on the M103 300E's.....too low in my opinion....

400Eric · #8 08-29-2016, 05:31 PM

Hi all.

Old thread I know, but it doesn't seem right to start a new thread on this topic. Much better to just pick up where this one left off.

I too want to use a gasser's trans in an 87 300D. Reasons being:
1) The 89 and later 722.3 trans has a lower 1st gear ratio --- 3.87 vs. 3.68 --- more giddy-up out of the hole!
2) Where am I gonna find another trans for a 87 300D? (The later W124 300Ds only use the puny 722.4 trans.) I suppose a W126/W140 OM603 trans could work but, again, still too rare.

I realize that there will be WOT shift point issues to overcome. Anything else?

Is there anybody here who has actually done such a swap?

Any help is appreciated!

Phillytwotank · #9 08-29-2016, 05:38 PM

You could look into going with a 722.6 transmission and add the electronic controller. I hear that is a bad ass upgrade

400Eric · #10 08-29-2016, 05:45 PM

Yes, that would be, but it's also more than I'm willing to try to tackle. This needs to be relatively cheap and simple for me or else it will never get done.

That swap would be especially nice because it would also allow me to run lower gears (higher numerically) in back for even more giddy-up!

Frank Reiner · #11 08-29-2016, 06:02 PM

Quote:

Originally Posted by 400Eric

Hi all. Old thread I know, but it doesn't seem right to start a new thread on this topic. Much better to just pick up where this one left off.

I too want to use a gasser's trans in an 87 300D.

The simple solution is to install the diesel trans valve body, vacuum modulator, and governor in the gasser trans.

Rrrockhound · #12 08-29-2016, 06:44 PM

Quote:

Originally Posted by Phillytwotank

You could look into going with a 722.6 transmission and add the electronic controller. I hear that is a bad ass upgrade

Not to hijack, but what would something like that run for a 300E? I hope my tranny lasts forever (well, 50K more miles) but I'm considering my options in case it doesn't.

Phillytwotank · #13 08-29-2016, 08:15 PM

Quote:

Originally Posted by Rrrockhound

Not to hijack, but what would something like that run for a 300E? I hope my tranny lasts forever (well, 50K more miles) but I'm considering my options in case it doesn't.

Just did a little quick searching. Looks like a used 722.6xx for diesel can be had for about $500. All the parts for the standalone tcu setup would be about a grand. Sure there are other things, driveshaft work maybe. Probably around two grand all in maybe.

400Eric · #14 08-29-2016, 10:54 PM

Philly, yes, it could be made to work, but again, there would be more time, effort and money than I am willing or able to invest.

Quote:

Originally Posted by Frank Reiner

The simple solution is to install the diesel trans valve body, vacuum modulator, and governor in the gasser trans.

That's my thinking too but my question is has anybody actually done this? Are there any unforeseen issues with compatibility?

Rrrockhound · #15 08-30-2016, 08:00 AM

Quote:

Originally Posted by Phillytwotank

Just did a little quick searching. Looks like a used 722.6xx for diesel can be had for about $500. All the parts for the standalone tcu setup would be about a grand. Sure there are other things, driveshaft work maybe. Probably around two grand all in maybe.

Thanks for checking. I assume a competent MB factory trained mechanic would be familiar with what needs to be done.