Once it started cooling off around here, I thought I had shelved the project for a while. I have a BMW 1 Series Coupe that I prefer to garage over the winter, which means the Benz gets driven full-time and I can't really afford for it to be down for anything longer than a weekend.

Well, the car had other plans. You may recall I mentioned the long cranks when warm, and we had theorized a fuel leak was to blame. I even noticed a little dampness on the top plate of the IP, so was pretty sure the DV seals were going bad. I figured it could wait until spring, and then I would decide what to do. But then all of a sudden my cranks got even longer - and weirder - starter would turn over really slow, like the battery was nearly dead, but then it would get better for a while, and then slow, slow, slow - until all of a sudden I was in a no start situation. Couldn't jump the battery, nothing.

So I took advantage of my roadside assistance plan and had the car towed to a local indy. Guy who specializes in Benzes and Sprinter vans. Tons of W123s and W124s in the yard, the kind of place that this car belongs. I figured it was something simple and not too expensive, but it was right before Christmas, and I didn't have the time or inclination to mess around diagnosing things and throwing money at parts that may or may not help. And I wanted the thing out of my driveway in the meantime.

Well, it turned out to be a couple of things: first, my 4-month old Bosch AGM battery is ****. It's funny, because I have the exact same battery in my BMW, only a little older, about a year. And it's also crapping out on me! So it looks like I have a warranty claim in my immediate future.

The second thing is in fact a fuel leak. DV seals, mainly, but also various hoses. So this guy wants a couple hundred bucks to fix the leaks, he's even going to throw in a "workshop battery" he had laying around from a previous customer's car to get me going. Once I deduct the cost of parts, I figure the balance is pretty reasonable for getting to keep from soaking myself in fuel.

But then I start thinking - it's pretty stupid to pay someone to do this job if I'm going to swap in this superpump I have sitting around in the garage. I've been wondering if I even really want to mess with it, it just seems like a whole 'nother rabbit hole to go down. But I bring it up to this guy anyway, just cause. I half expected him to tell me it was stupid, lol, and talk me into fixing the car up stock, but he's actually interested!

So I dropped the new IP off at the shop today. Guess it'll probably go in next week. Will have more to say about it then.

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Finally got the car back this week. It took my mechanic a while because, (1) he's pretty busy with the more routine jobs that are keeping his lights on, and (2) I think he had to do some research on getting this pump installed and set up right.

So, kind of a mixed bag. Besides the pump, a bunch of fuel hoses and clamps were replaced, and the fuel preheater was deleted. The motor starts right up as soon as you turn the key - hot, cold, whatever - it's very, very satisfying. It's a little "clackier" than the stock pump until warm. A little bit of black smoke until the turbo spools, but not bad. A lot of black smoke at WOT. The external ALDA is turned way down for the time being.

The bad news is my transmission is apparently shot. My mechanic says that he noticed the VCV on the old pump was maxed out, turned all the way up. Then when he went o pull vacuum on the tranny modulator, he says he got nothing, zero. Says the thrust pin was missing, which he replaced, and then was able to set it up to factory specs. But he says that so much time without vacuum likely ruined the transmission.

What I don't really get is that I thought that all the vacuum did was control the quality of the shift? IMO the car shifted fine, before this. In fact, I had another mechanic fiddling with the valve body shortly after I bought the car, and surely he would've noticed a lack of vacuum? Anyway, the quality of the shifts are worse than before, but still not terrible. The shift timing is a little weird. Off the line the car does pretty well shifting through the gears appropriately. But if I'm cruising in 4th, sometimes when I go to kick-down there's sort of a delay, and then the downshift comes a little too abruptly, and the transmission wants to hold onto the gear too long before upshifting.

My mechanic played around with pump and vacuum settings for a long time, but never did get it to a point where he was completely satisfied. He's suggesting a custom rebuilt 722.3, but hasn't given me a price yet. I'm not sure what the "custom" part is, but I wonder if the different gear ratios will be compatible with the car at all? In the meantime, I've found that after a couple of days of driving the car, I've sort of relearned the throttle sensitivity and mostly the car drives fine. Like I said, it's most noticeable during kick-down/WOT situations, which I'm largely avoiding anyway in order to keep EGTs down. I know the big thing these days is to retrofit a 722.6, but it requires an electronic controller, and overall is a much more complicated (and costly) proposition. Cool, though.

Which leads me to something else: I've kind of opened up a can of worms, at this point. Of course I knew it was coming, but taking this first step has obligated me to take a few more: I need to fix the turbo situation - it's obvious that the motor needs more air flow. I need to intercool - I have my eye on a kit that should work, I just need my mechanic to commit to the project, as it requires skills outside my repertoire. And I probably want a freer-flowing exhaust.

But, one thing at a time!

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Bob, I just realized your previous post said fuel delivery was set to 90cc. That is HUGE, should be enough to support nearly 300hp, and it's why you are seeing so much black smoke. Definitely turn it down if possible. For reference, a 6mm element pump maxes out at less than 80cc; and a stock OM603 six-cyl pump is ~52cc.

The transmission is a separate topic. A "shot" transmission will either not shift or go into gear, or slips / flares badly, and I haven't heard you mention any of those maladies. You are correct, the vacuum modulator controls shift firmness. With no vacuum it would shift firm all the time, which isn't pleasant at light throttle. Has a known-good vacuum modulator been installed and adjusted? Also, remember that the diesel vacuum modulator receives a vac signal entirely based on throttle position, more on this below.

Shift timing (rpm) is entirely based on throttle position, via the Bowden / control pressure cable. If the injection pump is pushing too little fuel (bad ALDA, stock pump out of adjustment, etc) this can result in late upshifts. The late upshifts will also be too firm because your foot is further into the throttle, reducing vacuum, making the shifts firm. The opposite is also true, with lots more fuel you aren't moving the throttle as much, so you would normally end up with early, soft shifts; maybe evening slipping/flaring if the vacuum level is high. I don't know what Dieselmeken recommends to get the transmission shifting appropriately.

Once your power gains become significant - basically once you get a larger turbo - the stock 722.4 transmission will be inadequate for the amount of torque produced. At that point you'll need to upgrade to a 722.3 which if built propery, can handle anything the 602 can put out with your Uberpump. The "custom" part likely just means an extra clutch pack internally (used on 6L M119 and M120 engins making 400hp with the 722.3) and possibly some fancy aftermarket friction discs. Nothing special should be needed. The donor trans will probably need to have a diesel valvebody in order to shift properly, I don't think a gas tranny will work without a lot of effort (if at all). If your mechanic hasn't done this stuff before, find a place that knows what they are doing! The driveshafts may also need to be replaced due to different lenghts.

BTW, what kind of EGT's are you seeing now, assuming you have an EGT gauge? It's possible that with a turbo upgrade and sensible fuel delivery settings you could avoid an intercooler for now, but an IC will be needed if you want to really turn the power up. Check out the liquid-to-air IC used on this S124 wagon build with a 606. Posts 7, 30, and 33 show a good amount of the plumbing:
https://www.*********.com/forums/showthread.php?t=11236

Edit: Replace the asterisks above with "500E board", with no space in between. Apparently, PeachParts has a problem with 500E's. Lame.

Apparently your mechanic doesn't understand how the vacuum system works. The vacuum portion of the transmission system is there to affect the quality of the shift. The VCV is a "set and forget" thing, there's no "adjustment" you can do to it. Make sure the throttle is against its stop (WOT), turn the VCV until you feel resistance, tighten bolts. That's pretty well it.

Adjusting the modulator is something you can do by the seat of your pants, or if you want to do it right, you can hook up a pressure gauge and tune it that way. Once it is set, leave it alone.

Shift timing is set with the bowden cable. Since you're making more horsepower than stock, you may need to play with it a bit to get the shift points right. If the gears are hanging too long, you may need to slacken up the cable a turn or two. Running without any vacuum to the modulator will cause abrupt/excessively-firm shifts, but shouldn't damage the transmission. A firm/abrupt shift is actually easier on the clutches and bands than a soft/sloppy shift is.

Does the '92 use the blue-ufo vacuum amplifier? If it does, make sure all of your vacuum and boost sense lines are going where they should be.

Keep in mind that you have an engine making more power than stock, so the stock settings may not be good enough anymore. Some fiddling will surely be required to keep it comfy. As long as you don't have real long delays shifting into gears or having flaring between gear changes, I'd say the transmission still has life left in it. I'd be far more worried about it if it were slow and mushy!

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

What part of the linkage gets adjusted exactly? Just any of the nuts to slacken the assembly, or does it have to be a specific one?

Not my pic, but for illustration purposes:


EDIT: Never mind! I looked more closely in real life and there's only one real way to adjust it; it's super easy. I made a minor change and noticed an immediate difference. I'll need to play around with it and test drive, of course, but it's pretty reassuring so far.

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It'll take a few tries to get the shifting in the right place. Once you get it where you want it, you can adjust the firmness by adjusting the modulator pressure. There's a rubber cover on it, pull it off then turn the T handle one increment at a time. CW is firmer, CCW is softer. I went through this dance with my SDL since it has the 3.5L injection pump on it. Once you get it dialed in, it should be pretty responsive and smooth.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

So I’m a little confused - I’m adjusting the throttle linkage, which certainly makes the pedal more sensitive (kind of like a throttle position sensor on a newer car), but isn’t really making the transmission behave differently, per se. It just means I can be less aggressive with the input. Am I adjusting the wrong thing?

In your photo above, the Bowden cable is on the passenger side of the valve cover. You should be adjusting that linkage that goes across the valve cover. It will tension or slacken the bowden cable. If the bowden cable has a threaded end, try turning it instead.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

On second thought I think the tranny is flaring. The upshifts seem soft and often late. In kick-down situation, the car really hesitates to downshift, and once it does, it is reluctant to upshift again, usually requiring me to ease off the gas a little to prompt the gear change.

Obviously, I will play around with the Bowden cable for a while, and then move on to the transmission modulator - but is there anything else I should be doing? I guess if it's flaring, then the transmission could really be bad - but it didn't seem to flare with the stock pump. Maybe because the vacuum was set to compensate?

What I'd really love is to just go to a manual tranny and take total control of my shifts, but that would obviously be a very involved and complicated (not to mention expensive!) proposition.

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When you're in a "kick-down situation" are you pressing the button behind the accelerator pedal, or are you just pressing the accelerator and expecting an automatic downshift? If the former, you could have a gummy downshift solenoid, or a bad kickdown switch (both are very common). If the latter, the transmission is entirely mechanical, if you want to force a downshift, hit the button to force one.

If you are triggering the downshift button, you have to back off it if you want the transmission to shift up at the normal RPM range. If you hold the downshift button down, the shift point will be several hundred RPM higher than normal. Useful if you're trying to accelerate very quickly!

Flaring is characterized by a sudden RPM increase right as the gear changes. Instead of the RPM rising as usual, then suddenly dropping when the gear changes, you'll have the RPM rising as usual, a sudden 2-300 RPM spike in engine RPM, then the gear change. If the shifts are just late and soft, that's a tuning issue not a wear issue.

Bowden cable will set WHERE the transmission shifts (it is formally called the load control cable). It's input will alter the governor's shift point based on throttle position. Tension the cable for higher/later shift points and slacken it for lower/earlier shift points. At WOT without engaging the kickdown switch, you should be changing gears somewhere around 4300-4500 RPM. 1-2 will usually happen a little earlier, but 2-3 and 3-4 should be roughly similar.

Vacuum modulator affects the quality of the shift. Without the vacuum input, all shifting would be very abrupt and firm. On a gasoline engine, the manifold vacuum is highest at idle and nearly nonexistent at WOT. On a diesel engine, there is no vacuum so it comes from the pump. The VCV is there to relay a "fake" vacuum signal based on throttle position. If you have the blue UFO vacuum amplifier, things get taken even further by adding in a boost signal to modify the vacuum signal even further.

Since there is a lot that's changed on your car I'd do the following (in order):
1: get a hold of the FSM for your year model and set the throttle linkages to the stock lengths. This will give you a baseline to adjust everything else.

2: Use the FSM procedure to adjust the VCV to its stock position. There's no point in trying to "tune" it, it won't do anything for you.

3: After doing 1 and 2 above, adjust the bowden cable until you just have tension on it.

4: Tee in a vacuum gauge in the line going to the transmission modulator and go for a ride. Sitting in idle, you should have something like 12-15" of vacuum going to the modulator. As you progress in throttle position, you should see the vacuum bleed off to 0. If you have the blue UFO, you'll see the vacuum at a given throttle input drop on its own as the turbo builds boost.

5: If the vacuum signal is where it should be, play with the bowden cable until you get the shiftpoints where you want them. Tightening the cable will delay the shift and make it happen at a higher RPM.

6: Once you have 1-5 done above, you can play with the modulator. If you're feeling ambitious, there are posts on this forum and elsewhere giving a chart for the modulator hydraulic pressure based on transmission model. Tie in a gauge to the modulator test port and test the pressure. Adjust the modulator until the pressure is where it should be. Alternately, you can play with the T handle until the shifting quality is acceptable. If too soft, turn 1 increment CW, if too firm, turn 1 increment CCW at a time. You should not have a silky smooth shift, you want a moderate, but refined shift. Too firm and you'll shatter your spine. Too soft and you'll wear the clutch packs prematurely.

Manual tranny swaps are certainly an option, but keep in mind that the auto will actually be faster since the boost doesn't drop off during every gear change. The 722.4 is a relatively "weak" transmission. Since you're making more power than stock, you may consider upgrading to a 722.3 at some point in the future. I'd personally ride that 722.4 into the ground, then replace it just to maximize my investment in the car (but I'm also cheap!).

Also, if you're still reading....sorry for the long post!

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thanks for the in depth post - I appreciate it! Will get started and try to get it sorted out myself.

And I'm with you - I plan on sticking with this tranny as long as possible. Given the way it performed beforehand (with the stock pump), I'm inclined to believe it's more a matter of not being set up right at the moment, than anything else.

__________________

I LOVE THIS THREAD SO MUCH...

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1991 300D 2.5 "Rocinante"
2002 Golf TDI "Teen Spirit"
--------------------
1984 300D
1966 Mustang I6 3sp
1985 Mazda RX-7 GSLSE
1982 Toyota Supra
1977 Datsun 280z
1971 Datsun 240z

Thanks!

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You know, after playing with the throttle linkage length a little bit for a few days, and relearning smooth but assertive inputs on the go pedal, I think I've got the car set up pretty sweet. Even chirped the tires a few times! I find I'm almost never up over 3000RPM before I'm going to fast for the roads around her, that is, unless I'm merging into traffic from a dead stop or something.

I probably still will play with the tranny modulator a little next time I'm under the car, and I'm really prioritizing a turbo swap, maybe this summer, when I'm back to DDing the BMW. I think the power band will just be so much sweeter with a little more whoosh, plus I reckon it will run cooler and with less smoke.

The 722.4 seems to be doing fine. I mean, it probably won't last forever, but for now it seems okay.

The other big piece is the chassis work. I have probably 2/3 of what I need, not counting the time, of course.

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