Setting up a 722.4 with a Superpump
Setting up a 722.4 with a Superpump
So any advice on setting this up properly? I'm messing around with the Bowden cable to try and get the timing right, and then I will try to firm up the shifts a bit by messing with the vacuum modulator - but is there anything else I should be doing?
My mechanic thinks the transmission is shot, and thinks I should swap in a 722.3. But the things is, the tranny didn't seem to have this problem with the stock pump, and wouldn't a 722.3 have the same issues as a 722.4, since it is vacuum-controlled? I know a 722.6 is sort of the cool thing to do, but I'm afraid it would incur too much expense, and require too much expertise, to retrofit easily. What I'd really love is a manual transmission, but that is a pretty involved project, too, obviously.
I guess what I need to know now is if there is anyone with specific experience getting the 722.4 to work as well as possible while I research better options for a definitive fix. I know if I continue down this road, I will probably need something stronger than the 722.4 anyway, but I'm just trying to make the car more drivable in the meantime.
Bummer-Bob
02-24-2018, 12:35 AM #1So I recently put a Dieselmeken 7,5mm Superpump in my 1992 300D 2.5. For those of you who don't know, this is the US-version of the 250D (W124), with the OM602 engine and the 722.4 transmission. Motor runs great with the new pump, but the transmission is misbehaving slightly. I think the VCV is different than stock, but (at least the way I have it set up now) the shift quality doesn't seem to be suffering to much...well, it's not harsh, at least. I think the transmission might be flaring a little. The shifts are soft, and the tranny kind of hunts sometimes. When I activate kick-down, it takes a couple of seconds to downshift, and then often holdes the lower gear for too long before upshifting again (usually I have to ease off the gas to prompt the upshift). And any times the shift points just seem odd.
So any advice on setting this up properly? I'm messing around with the Bowden cable to try and get the timing right, and then I will try to firm up the shifts a bit by messing with the vacuum modulator - but is there anything else I should be doing?
My mechanic thinks the transmission is shot, and thinks I should swap in a 722.3. But the things is, the tranny didn't seem to have this problem with the stock pump, and wouldn't a 722.3 have the same issues as a 722.4, since it is vacuum-controlled? I know a 722.6 is sort of the cool thing to do, but I'm afraid it would incur too much expense, and require too much expertise, to retrofit easily. What I'd really love is a manual transmission, but that is a pretty involved project, too, obviously.
I guess what I need to know now is if there is anyone with specific experience getting the 722.4 to work as well as possible while I research better options for a definitive fix. I know if I continue down this road, I will probably need something stronger than the 722.4 anyway, but I'm just trying to make the car more drivable in the meantime.
all that aside to verify the vac controller system is functioning look at the vac supply going to your VCV from the pump it should be 15-22"HG vacuum then verify the vent line on the side is clear. if all thats good check the modulator on the trans and the line going to it for leaks the output from the VCV to the modulator should be slightly below the input vac at idle and quickly decrease to zero vacuum as you feed it throttle. once you verify everything is working ok then i would start tuning the bowden for your shift points and the modulator to prevent flaring. depending on which style modulator you have you may be limited by how much more you can give it. if it is the style with the T handle i would start with a full turn and add or remove from there depending on if it is flaring during shifts with heavy throttle. if it had a molded plastic handle that can only turn 1/3 or so i would just max it out. it would also be a good idea to go ahead and change the fluid and filter on your transmission to help head off any issues with loss of line pressure or fluid degradation.
85 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
the main issue is the 722.4 transmission is significantly less robust than the .3. i doubt it would last long behind a 7.5mm pump as they regularly die behind 2.8 m104's and the stock 602's. i have had to replace 3 in the last year on customer cars that are entirely stock they let go at the rivets on the first clutch pack.
all that aside to verify the vac controller system is functioning look at the vac supply going to your VCV from the pump it should be 15-22"HG vacuum then verify the vent line on the side is clear. if all thats good check the modulator on the trans and the line going to it for leaks the output from the VCV to the modulator should be slightly below the input vac at idle and quickly decrease to zero vacuum as you feed it throttle. once you verify everything is working ok then i would start tuning the bowden for your shift points and the modulator to prevent flaring. depending on which style modulator you have you may be limited by how much more you can give it. if it is the style with the T handle i would start with a full turn and add or remove from there depending on if it is flaring during shifts with heavy throttle. if it had a molded plastic handle that can only turn 1/3 or so i would just max it out. it would also be a good idea to go ahead and change the fluid and filter on your transmission to help head off any issues with loss of line pressure or fluid degradation.
85 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
I might be getting rid of my .3 soon, but shipping might be a nightmare....
(02-24-2018, 07:23 PM)polarisrmk Throw away the 722.4 and get a 722.3
Aren't the transmission internals configured differently for gas vs. diesel? The torque ranges are quite different. By the time the gas engine is starting to really pull, the diesel is in need of the next gear. Can that be compensated for?
(02-24-2018, 07:23 PM)polarisrmk Throw away the 722.4 and get a 722.3
Aren't the transmission internals configured differently for gas vs. diesel? The torque ranges are quite different. By the time the gas engine is starting to really pull, the diesel is in need of the next gear. Can that be compensated for?
85 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
the transmission gearing is the same between the gas and diesel. there is a slight difference in the governor tuning but that can be adjusted on the valve body easily. also the diesels rev relatively high while the gas engines are mostly not that fast turning. so it works out similar. the main difference is the rear end gearing.
85 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
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