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Discussion Starter #1
So yesterday my 722.4 trans decided to start exhibiting really odd behaviors. It would start up-shifting almost immediately upon off-idle throttle, so that it was already in third by the time I reached 20mph--drove like a dog. I had been planning on driving it down to Salem today, but ended up taking the gf's Audi. I know I might be able to diagnose the problem, though I've checked the kickdown cable and fluid levels, but nothing seems obvious. I have a 722.3 trans from an '87 300TD I recently stripped. It came with documentation showing that it was an MB factory rebuild about 60k ago, so I'm going to swap it in there. I think I'll just use the forward portion of the six cylinder driveshaft, since the two transmissions are physically different lengths. I guess I'll use the 722.3 torque converter too, but I've heard the later 722.4 trans have a different stall speed. I'll take pics and document my journey over the weekend.
 

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The output flange, cooler line banjos and NSS connector are different.

Just replace the kickdown cable?
 

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The speedo output is different also. You will need to transplant the drive mechanism from the 722.4
Different 1, 2, 3 gear ratios also.
 

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Discussion Starter #4
I dropped the trans this evening. I did not enjoy the experience. I'll take pics tomorrow when I'm tanned, rested and ready. The NSS is definitely different, as is the forward driveshaft section. I didn't measure, but I think the pump drive input is smaller on the 722.4 TC. I'll dissect this thing at a later juncture, but I've really never been happy with the trans in the car, and have been looking for an excuse to step up to the superior 722.3. Fact is, I have three spare 722.3 transmissions taking up space in my shop, so it's not a huge investment except for all the frustration and annoyance. I've never pulled one of these things without also yanking the engine at the same time.
 

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Discussion Starter #5
OK, I've taken some pics of the two transmissions, and there are a striking number of differences.





722.4
  • front drive shaft section = 76.5 cm
  • torque converter pump drive = 35 mm
722.3
  • front drive shaft section = 73 cm
  • torque converter pump drive = 43 mm
Additionally, as mentioned the NSS is different, as is the kickdown cable. I'm hoping the 722.3 NSS harness and cable can be swapped over. I'll be glad to finally get rid of the funky 722.4 drive shaft harmonic dampner that was ready to shred at any time. I suppose I should mention that the trans output yoke is larger on the 722.3 unit.





 

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Discussion Starter #6
And as mentioned earlier, the cooling line banjos are indeed different, so add those to the mix. I'm not sure about the speedo drive though, as they look identical.
 

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Discussion Starter #7 (Edited)
SUCCESS!

Wow, that was a really unpleasant little project, but the end result exceeds my expectations. Some background--I'm a bit of a claustrophobe, so crawling around under the mid-section of cars, with grease and dirt falling into my eyes, ears and hair is pretty taxing. This job would be so so so much easier with a proper lift, but I had to make do.



I ended up using the complete 722.4 driveshaft, because the 722.3 forward section ended up being too short coupled to the former's rear section. My 722.3 driveshaft also had a sketchy support bearing and rear flex disc. So unfortunately I had to pull the smaller yoke off the old trans and fit it to the new one. Since my engine already pumps out more power, I'm not pleased about this, so I'll rebuild the 722.3 driveshaft and install it later.



I'll bet most of you haven't seen one of these bellows before, as I'm pretty sure they're nearly all AWOL on these older cars. Part # 202 411 04 97



In addition to the NSS cable and cooler lines, I also needed the 722.3 shift rod and dipstick tube.





The left side cooler line pretty much installed exactly as before, but the right side needed some creative tubing bends in order to clear the turbo drain pipe and sump "hump". Don't forget to replace the dead or missing rubber tubing clamp bushings. I used plastic cable wrap cut to size.

As mentioned, I'm very pleased with the outcome. The shifts are firm and crisp, with zero lag from park to either reverse or drive. The big one for me is the fact that I can now drop the hammer and downshift immediately under both low and high speeds. I never could get the 722.4 to consistently replicate these downshifts. I got used to manually downshifting when the situation called for it. I doubt very many of you will follow suit, but if the opportunity presents, I highly recommend this upgrade. Just remember the following 722.3 additional parts:

  • NSS cable
  • Dipstick tube + dipstick
  • Shift rod
  • Cooler lines
  • Torque converter
  • *optional complete driveshaft and diff yoke
 

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Discussion Starter #9
Thanks. What's a good test of TC performance I can use to judge? The overall responsiveness is like night and day
 

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That is odd...my 87 260E has a 722.4 and the housing is not like yours...Its shaped like the 722.3.

Maybe they changed the look of the housing? Also, that flex disk looks different too. I checked the part # on the side of my transmission and it states 722.4.

Odd :confused:

I personally can't tell a difference between the .3 and .4...in fact, my .4 shifts much firmer and quicker than the .3 even after its been rebuilt! Its almost like it has a race shift kit in it.

EDIT: Now I look at your photo's, something doesn't add up -- why do you have a rear pump? Unless my eyes are bad, its definitely got a rear pump.
 

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All MB trannies had rear pumps up until around 1993 or 1994, I think? Then they deleted the rear pump as a cost-savings measure. During a rebuild, the pump is usually removed and replaced with a blank plate instead (again, cost savings).

Casey, on my '87, I notice that the revs will go up to near 3k under medium/heavy throttle, even when the car isn't moving anywhere near fast enough to warrant those RPM's. And when going on/off the throttle at freeway speeds, the rev swing would be like 600rpm.

On the '93, I recall the converter being "tighter" where it wouldn't shoot to 3k at low speeds, and when going on/off the throttle at freeway speeds, the rev swing was only like 200rpm. However, I haven't driven the '93 in a few years since I sold it to my sis...

:)
 

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I thought that no 722.4 had a rear pump and it was included only on the 722.3...
 

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I thought that no 722.4 had a rear pump and it was included only on the 722.3...
EPC shows that a secondary pump was included on the 722.4 up to a certain transmission number. If yours doesn't have it, either your tranny was past the cutoff point, or it was rebuilt in the past and the rebuilder deleted the pump.

:eek:
 

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I always had this funny feeling its been rebuilt...but no proof other than the fact its immaculately clean and rest of the engine and transmission tunnel is oily.

Maybe that's it then. It shifts incredibly. When I eventually part it out, I'd love to pass it on to someone on here (I'd reseal the front pump) since its really, really impressive.
 

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You can check the serial number on the tranny against the EPC datacard. If they don't match, it's definitely a rebuild.

If the serial numbers DO match, it could be that a shop rebuilt the original trans, rather than buying an "exchange" unit and returning a core, which is the more common method.

:)
 

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OMG!!!

I thought that this is a Plug&Play swap. I have a 722.3 ready to be installed in my 300E. Now I see that I need more parts...

If I have the 722.3 shifter with the wiring harness, do I need to swap NSS?
 

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A 300E should already have the 722.3 from the factory. I'm not aware of any M103 motors being supplied with the 722.4 trans. That was only on the W124 diesels, such as the 300D, 300TD and E300 DIESEL in both turbo and non-turbo flavors.
 

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Discussion Starter #20 (Edited)
OMG!!!

I thought that this is a Plug&Play swap. I have a 722.3 ready to be installed in my 300E. Now I see that I need more parts...

If I have the 722.3 shifter with the wiring harness, do I need to swap NSS?
I haven't checked the wiring diagram, but I assume the NSS plugs into a starter relay from the plug in the drivers side footwell. Theoretically you can probably cobble together an NSS harness (not recommended), but the most important things to gather are the cooler lines meant for a 722.3. The Shift rod and dipstick tube can probably be modified to work, but it wouldn't be much fun to try and solder on the correct size and orientation banjos on the end of the cooler lines.

Just to be clear, the two different NSS cannot be swapped, as they are physically quite different.

edit: I'm also wondering if you need the coolant lines (and possibly the dipstick tube) from an M104 engine, rather than an M103
 
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