Are 124 transmission interchangeable? - Page 3 - PeachParts Mercedes-Benz Forum

400Eric · #31 08-31-2016, 01:43 AM

Quote:

Originally Posted by Stretch

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.

400Eric · #32 08-31-2016, 01:53 AM

Quote:

Originally Posted by Frank Reiner

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.

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?

Frank Reiner · #33 08-31-2016, 12:23 PM

Quote:

Originally Posted by 400Eric

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.

400Eric · #34 08-31-2016, 05:55 PM

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?

Frank Reiner · #35 08-31-2016, 06:28 PM

Quote:

Originally Posted by 400Eric

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".

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.]

400Eric · #36 08-31-2016, 06:54 PM

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.

Frank Reiner · #37 08-31-2016, 08:09 PM

Quote:

Originally Posted by 400Eric

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.

400Eric · #38 09-01-2016, 03:04 AM

I'll disconnect the solenoid and report back Thursday.

400Eric · #39 09-01-2016, 03:07 AM

Quote:

Originally Posted by tjts1

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.

You have a PM.

400Eric · #40 09-01-2016, 03:43 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.

400Eric · #41 09-09-2016, 02:43 PM

Quote:

Originally Posted by tjts1

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.

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

400Eric · #42 09-13-2016, 02:50 PM

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?

Frank Reiner · #43 09-13-2016, 04:04 PM

Quote:

Originally Posted by 400Eric

Can I use a gasser 722.3 trans?

Once again, yes; see post #11.

400Eric · #44 09-14-2016, 04:07 AM

Yes, post #11 :

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.

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.