Are 124 transmission interchangeable?
 

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

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.

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

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

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.

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....

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!

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

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!

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

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.

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.

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

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

If you're looking for more off-the-line, look into some changes to your turbo and IP, you'll spin the tires with your stock gears.

Yes, I'll be doing that stuff (and more), but right now I need to address this needing-a-trans issue, and I might as well do a first gear upgrade while I'm at it, with a much more readily available trans.

Do you have a build thread for your OM603 car that I could learn from? Are there any others? I've actually been looking and all I can find is crazy turbo-sticking-out-of-the-hood kind of builds. I'd eventually like to have this car running low 14s but for now low-15s will do. Twelves are not needed here. Even GSXR doesn't seem to have a build thread anywhere. A lot of good info on his site, yes, but no actual build thread. A general internet search just produces the crazy stuff.

I also want to mention that in another thread I talked about how I proved that the fuel pump relay does indeed affect the shift points at WOT on my CIS-E cars. This proved that it wasn't just the bowden cable, modulator, governor, and valve body controlling the shifts. How would a trans that comes from such a car be controlled here?

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

I blazed my own trail when I hopped up my 400E. I had to be the one who did everything for the first time cause nobody else had ever done it before. I can't afford to be a trailblazer here. OM603s are too expensive and too hard to find.

I don't know of a build thread however, Dave (and later I also) did chronical some of his build here: http://www.peachparts.com/shopforum/diesel-performance-tuning/290694-om603-semi-super-pump-testing-fitted-bosch-6-0mm-elements.html

and another member posted some of his updates here: http://www.peachparts.com/shopforum/diesel-discussion/375617-om603-722-6-w124-adventures.html

There are others who have made changes to the 603-powered cars at different levels, these are the ones that come to mind first.

Thanks big time for those links Jeff!!

Still need to hear from OM603 owners who are running a gasser 722.3 trans.

And a link to that thread, if you please.

OK Frank here are the two posts where I documented my findings on the matter:

http://www.peachparts.com/shopforum/performance-paddock/245997-tuning-cis-21.html#post2792781

http://www.peachparts.com/shopforum/performance-paddock/245997-tuning-cis-21.html#post2793540

This Fuel Pump Relay discussion occurred as part of a larger discussion on tuning CIS-E cars. If you have the time, go ahead and read the whole thread after my first link. Lots of heady stuff in there if you are into CIS-E cars! In fact, better yet, read the whole thread from the beginning!

I have a good 87 300d trans that was rebuilt by the previous owner sitting in my garage. I swapped it out for a 5spd.

I'm re-reading that thread myself and according to Dave in the first paragraph of this post: http://www.peachparts.com/shopforum/2793063-post309.html on the 300D my klima relay controls the WOT shift point so hopefully the new gasser trans will obey the 300D's klima relay and shift earlier for it's new diesel partner. It would be nice if that issue is solved that easily. That Dave. Even when he's not around he helps.

Anybody out there actually done a swap like this?

Can I come clean out your garage for you?

Since the Klima relay controls the power supply to the Kickdown (KD) switch, when the set speed (RPM) is reached, power to the KD circuit is interrupted, causing an upshift. The KD circuit simply does not know the provenance of the transmission.

Could a defective Klima relay prevent an otherwise healthy trans from shifting into fourth gear and delay up-shifts in the other gears? If I could get to the bottom of this tranny's funky behavior I might not need to swap in another trans. I'm studying other threads on this topic as we speak and I'm trying different things. TBH, this trans seems too healthy and strong to be replaced. It's as if something (like a defective relay or kickdown switch) is telling it: "don't shift yet".

No, the relay is a power supply to the KD circuit; a fault in the relay that cut off power to the KD circuit would result in early WOT shifts.
A fault in the KD switch, or in the "B" switch in the gear selector, that caused the KD solenoid to be energized, would result in late shifts.

Please tell me more about the "B" switch.

4E:

Most selectors for the 722.3xx transmissions that start in 2nd have a notch to the right of the "L" position. The lever can be pulled back to the "L" position, and then pushed to the right, causing the trans to shift to 1st. Pushing the lever to the right closes a parallel circuit to the KD solenoid. In effect, it is a hand operated KD switch.

I think the 722.6 is a bit bulkier (size-wise) and might need modification to the chassis to make it fit whereas I don't think that would be necessary going from 722.4 to 722.3 on a W124

This OM603 powered W124 already has a 722.3 unlike the later OM602 powered W124s which have the 722.4 trans. I'm simply pondering a 722.3 gasser trans swap in place of my 722.3 diesel trans.

That "to the right" position exists only on my 400E and my E420, but not on any of my other W124s, so I guess that just leaves me with the KD switch. But even here there is confusion. I appear to have a KD switch under the go pedal (can't call it a "gas" pedal), and I also have a KD switch under and just forward of the bowden cable under the hood. What's the story on that one under the hood? What is it for?

The engine-mounted microswitch that is actuated by the throttle linkage is to provide WOT cancellation of EGR, and shutoff of the A/C compressor.

Oh, OK, that would explain why the 4th gear problem wasn't helped by the disconnection of that switch. Thanks for your help Frank!

So where should I go from here?

Back to this post;
1) How about a detailed description of the shifts, both part-throttle, and WOT, as you are driving now.
AND
2) The behavior of the shifts with the wire removed from the KD solenoid. [Tape the wire terminal.]

Part throttle shifts are delayed. Wants to hold it's gears forever. Only shifts when you let off the pedal or let it wind out till it finally shifts on it's own. When it does shift they are firm, with no clunking or jerking, or flaring, or any other behavior that would indicate trouble with the trans itself. WOT shifts are perfect, and occur when they should (except 4th of course).

I pulled the plug to the KD switch under the pedal, no change. Do I still need to pull the wire from the KD solenoid too?

There is a tranny "cold shift softener" switch over valve, as seen here on Dave's site http://www.w124performance.com/images/OM603_injection/cruise_fix_before.jpg
Could a malfunction here cause an issue? I haven't tryed to bypass that thing yet cause I wouldn't know where to start.

The thought behind disconnecting the solenoid is that there could be a fault (short between the two wires) in the KD switch harness.

The "cold shift softener" increases vacuum to the modulator before the engine is up to temperature. It is possible that a leak to atmosphere in the modulator vacuum hoses could raise the shift points; that leak would make all the shifts quite harsh.

Although the modulator has some effect on part-throttle shift points, they are primarily controlled by throttle position, via the Bowden cable.

I'll disconnect the solenoid and report back Thursday.

You have a PM.

No change, still no 4th.

Today I noticed something I hadn't noticed before. I don't seem to have any engine braking in 2nd gear. Could this possibly be related? Now I'm not so sure about the condition of this trans. Diesel or not, I'm still supposed to have engine braking in 2nd aren't I?

Tjts1, please get back to me about your trans.

Tjts, could you please PM me back about this trans?

Did the "T" bar mod today. Went 5 and a half turns, till I felt some resistance. Very unexpected results. Part throttle shifts are now right on time, and nice and crisp. It now tries to go into 4th, but can't, it just free revs instead. After a couple of miles with the trans now properly warmed up, it goes back to it's old behavior, which was and is just staying in 3rd, making no attempt to go into 4th. So now I'm thinking that it's a K-2 piston issue, but reverse is also dependent on K-2 and reverse seems fine. So still no 4th but I'm still glad I did the T bar mod anyways because the first three gears are working splendidly now.

So what is the final verdict here? Tjts1 isn't sure if he wants to sell his trans. I can get a gasser trans for next to nothing anyways, and now get the benefit of a lower first gear ratio to boot. Can I use a gasser 722.3 trans?

Once again, yes; see post #11.

Yes, post #11 :

I had taken that to mean how it should be done, but I wanted to know for sure that that is how someone has already done it. In other words, we are talking about something that has actually happened, correct? Somebody has actually done this swap and this is how they did it, correct? Not just theory, but fact? I just really need to be sure here. As I said before, I can't afford to be a trailblazer here. I have neither the time or the money right now.

Please don't get me wrong here, I really do appreciate your help Frank. You know how easily the printed word can be misinterpreted. Just trying to get the facts right.