Another 603 vacuum adjustment/shifting thread... help Brian, Dave, etc.!

[AlexTheSeal]

Hi guys,

I have a hard-shifting transmission on my '87 300D. I've been doing a lot of diagnostic work and parts replacement and have read just about every thread here on the issue, but my symptoms aren't quite the same as any I've read about.

My vacuum pump, vacuum control valve, and transmission vacuum modulator are all new. I have been through literally every vacuum line and connector on the car and replaced quite a few that tested bad; there are no leaks to speak of. In particular, the lines to the EGR and ARV are capped, and the ACC vacuum subsystem is tight (tested at the manifold behind the glove compartment). The ALDA could stand a tweak, but off-the-line performance is adequate so I haven't done it yet. The transmission fluid and filter are fairly new (10K mi or so) and I think the level is correct, although I always have a hard time reading the dipstick.

The new vacuum pump is putting out a steady 25 inches of mercury. When I replaced the VCV, I adjusted it to output 14 inches at idle. I have a tranny pressure test gauge, and I adjusted the new modulator correctly (with the vacuum line disconnected, and to the pressure from the TDM [I forget what the spec is now]).

I've been driving the car with my MityVac teed into the line from the top of the vacuum amplifier to the transmission modulator, and am seeing pretty consistent behavior:

• At a warm start, the vacuum amp puts out about 5 in. If I leave the car idling, this slowly (over the course of a few minutes) rises to about 12-13 in.
  
• Any accelerator input, even a very light touch, drops the output back to 5 in. For example, the amount of "throttle" needed to keep the car going a steady 25 mph on a flat road puts the vacuum amp output at a steady 5 in.
  
• Pushing the accelerator down any further causes the MityVac gauge to drop to zero almost immediately. When I let up on the pedal, it slowly (over ten seconds or so) rises back to 5 (or higher if the car is just sitting and idling).

From my reading of how the vacuum amp is supposed to work, this doesn't seem right. I expected output at idle to be nearly as high as the reading directly from the VCV (even allowing for the MityVac bleeding off some vacuum). And output above idle, I think, should be inversely proportional to accelerator position, in other words gradually tending towards zero as the pedal goes down. Last, I would think that response to letting off the accelerator would be quicker, so as (for example) to smooth out an upshift after accelerating to cruising speed and letting off the pedal.

Any thoughts here? If it's just that the vacuum amp is bad, that's fine---I've replaced practically everything else, and I wouldn't be surprised if the flying saucer were bad too! But I want to make sure there isn't anything else I'm overlooking.

[aersloat]

If you think that your ALDA needs a tweak then start there. My shifting changed dramatically when I adjusted the ALDA. Where in Portland are you? Removing and adjusting the ALDA only takes half an hour or so (including removing the windshield wiper reservoir) once you have done it a few times, which I have. Drop by some time-- we could probably adjust it pretty quickly.

[AlexTheSeal]

I understand how cranking up the ALDA could affect part-throttle shifting, but it shouldn't have any effect on vacuum coming from the amplifier at idle, as I understand it.

[gsxr]

1) The ALDA has a significant effect on part throttle shifting - I would definitely adjust the ALDA. It has no effect on full-throttle (redline) shifts.

2) The VCV (on the side of the IP) is not adjusted with a vacuum gauge. This MUST be adjusted per the factory procedure. It's a black/white, zero/one, yes/no, binary adjustment. It's either correct or it's not, there is no gray area. I've tried to adjust shifting softer/firmer by moving it a little one way or the other in the slots, and all it does is make the tranny shift screwy. I can't explain it, I don't understand it, I just know that on several '87 300D's it's done the same thing. The factory procedure is at this link (200kb PDF file). Note that the adjustment is done with the engine off and there is no mention of setting to a particular vacuum reading. Usually it will end up right in the middle of the adjuting slots.

3) The modulator pressure should be set with the gauge as a rough guide, but otherwise it's set by seat of the pants. Basically you want it so there is zero flare at full throttle shifts, and no firmer. This is not always where the pressure gauge says it should be. There's even a note in the WIS about ignoring the gauge when the shifts are off. You might want to check out the 722.3 diagnostics at this link (1.5MB PDF file).

4) Make sure the pressure line from the ALDA to the BFS (blue flying saucer) is clean and all the lines (both vacuum AND pressure) in that area have solid rubber connectors... sometimes the ones underneath, out of sight, can crack and leak. (Don't ask how I know!)

[AlexTheSeal]

So, an afternoon's work and a few test drives later...

1. I R&Rd the ALDA, which wasn't hard at all---I don't know why I was so scared of it all this time. Did the requisite one-and-a-quarter turn counterclockwise. Wow, what a difference! I wish I hadn't broken the nipple off the top of the shutoff valve with the Channel-locks, though.

2. I adjusted the VCV according to the PDF above, and while I had the ALDA out and access was improved I also followed the procedure in the FSM to set the length of the linkage rods, the Bowden cable, etc... everything was messed up there. How could the vertical rod that goes roughly from the end of the accelerator cable down near the kickdown switch be two centimeters shorter than spec? (You do measure them between the centers of the sockets, right? That's the only way that made sense to me.) I guess somebody tweaked the linkage to improve shifting and didn't know what they were doing.

3. I have crisp but not clunky shifting in all gears now at part throttle, very light shifting at idle, and, at full throttle, a little bit of flare on the 1-2 shift but not on the others. Guess I need to adjust the modulator one direction or the other.

4. I went over the system again for vacuum and pressure leaks and did indeed find them in the connections under the BFS. In fact, I replaced every soft air line under the hood and tested all the hard lines individually with the Mity-Vac (none needed to be replaced). I still have a slight vacuum leak somewhere, I believe, based on the Mity-Vac readings on the line coming off the BFS to the modulator:

• I'm now seeing about 15 inches at idle, 10 at part throttle, and 5 at full throttle.
• However, the vacuum at idle only reaches 15 inches after the car's been sitting for a minute or so. Whenever it drops (i.e. with accelerator operation) it takes a LONG time to come back up.
• Also, the reading doesn't seem to be affected at all by whether the turbo is spinning or not. I don't have a boost gauge yet, but I am pretty sure I'm getting decent boost, and isn't the change in manifold pressure when the turbo comes online supposed to influence the BFS?
• Nor does adjusting the hidden plastic adjustment nut on the bottom of the BFS seem to affect its output at all. (I was afraid to turn it more than a complete turn in either direction, though.)

So it seems like there must still be a problem somewhere. But I have no idea how to test the BFS independently for proper operation, nor the two pressure switches next to it. The lines to and between them are clear and tight, I know that---but how do I know that those components are working and not leaking? In particular, the BFS and the switch next to it both connect pretty directly to the vacuum pump, so if they're leaking I fear all my other adjustments are in vain.

[justinperkins]

I don't have anything to offer this thread, but I am watching it closely as I need to do the same thing to my wagon as I am experiencing flaring at full throttle between 3-4 and sometimes 2-3.

I am very thankful at the knowledge shown in this thread by Dave and Alex. Thanks guys

[AlexTheSeal]

Justin, if the only symptom you're seeing is flaring, it's more likely that your tranny is just low on fluid and/or could benefit from a fluid and filter change.

[gsxr]

Originally Posted by justinperkins

I don't have anything to offer this thread, but I am watching it closely as I need to do the same thing to my wagon as I am experiencing flaring at full throttle between 3-4 and sometimes 2-3.

I am very thankful at the knowledge shown in this thread by Dave and Alex. Thanks guys

Justin, for a FULL THROTTLE flare, first check fluid & filter as Alex said (or just change it, if it's due). Next, adjust the modulator about 1/2 turn at a time until the flare goes away. It's not likely you'll need more than 1 or 2 turns. If it's not going away, try a test run with the vacuum line removed (to make sure there's no vac signal present at full throttle). If the shifts are firm, you have a vac/plumbing problem. It's more likely that you just need to tweak the modulator a little.

Note that Alex's problems were at PART throttle, which is totally different.

[gsxr]

Originally Posted by AlexTheSeal

3. I have crisp but not clunky shifting in all gears now at part throttle, very light shifting at idle, and, at full throttle, a little bit of flare on the 1-2 shift but not on the others. Guess I need to adjust the modulator one direction or the other.

Yes - for a full-throttle flare, tweak the modulator *slightly*. You want it just at the point where flare is zero. Probably won't be more than 1 turn, maybe less.

Originally Posted by AlexTheSeal

• I'm now seeing about 15 inches at idle, 10 at part throttle, and 5 at full throttle.
• However, the vacuum at idle only reaches 15 inches after the car's been sitting for a minute or so. Whenever it drops (i.e. with accelerator operation) it takes a LONG time to come back up.
• Also, the reading doesn't seem to be affected at all by whether the turbo is spinning or not. I don't have a boost gauge yet, but I am pretty sure I'm getting decent boost, and isn't the change in manifold pressure when the turbo comes online supposed to influence the BFS?
• Nor does adjusting the hidden plastic adjustment nut on the bottom of the BFS seem to affect its output at all. (I was afraid to turn it more than a complete turn in either direction, though.)

15" is normal... the VCV drops the vac pump feed of 25" down to 15". The function of the BFS is, mainly, to prevent "full hard" shifts unless boost is present. However you need to have the engine under significant load to build boost. It helps if you have a boost gauge to watch. Usually, the BFS doesn't fail, and never requires adjustment, unless you're really picky about shifting. I only know one guy (Justin Dobbs, aka 'JRD') who adjusted the BFS and improved shifting a little bit. I've never touched mine.

Originally Posted by AlexTheSeal

So it seems like there must still be a problem somewhere. But I have no idea how to test the BFS independently for proper operation, nor the two pressure switches next to it. The lines to and between them are clear and tight, I know that---but how do I know that those components are working and not leaking? In particular, the BFS and the switch next to it both connect pretty directly to the vacuum pump, so if they're leaking I fear all my other adjustments are in vain.

I don't think there's still a problem, other than removing the slight full-throttle flare. You do want to make sure the boost signal tubes (and fittings) to the BFS are clean, and make sure the switchover valves near it are not plugged. One is the overboost protection, the other is the "cold shift softener", which disconnects the boost signal to the BFS when the engine temp is below 50°C. (The 50°C switch is directly above the thermostat, btw.) I disconnected this on my car because it would cause a FLARE when the engine was cold! I intend to remove the valve and change the plumbing too, but I haven't had time. If there is a third solenoid, your car has the "cruise surge fix" installed... I also removed this, because it reduces part-throttle power, by adding a restriction in the line from the manifold to the ALDA except at WOT. Killing the EGR and ARV cured the cruise surge. Here's photos from my old white '87:

Before:


After:

[AlexTheSeal]

Originally Posted by gsxr

Yes - for a full-throttle flare, tweak the modulator *slightly*. You want it just at the point where flare is zero. Probably won't be more than 1 turn, maybe less.

Is one full turn a slight tweak? I thought maybe the notches into which the T-handle in the modulator fits were there to indicate the preferred tweak interval.

You do want to make sure the boost signal tubes (and fittings) to the BFS are clean, and make sure the switchover valves near it are not plugged.

OK... how do I know that they are not plugged and/or leaking? Apply vacuum with the MityVac to the vacuum inputs on the one? See if the other passes pressure through when energized or vice versa? I'm at a loss. Do they act more like relays (on/off) or more like transistors (sensitive to variable voltage or resistance?

[gsxr]

Originally Posted by AlexTheSeal

Is one full turn a slight tweak? I thought maybe the notches into which the T-handle in the modulator fits were there to indicate the preferred tweak interval.

Try a half-turn at a time. "Slight" is one or two notches. If you go too firm at WOT, all the part throttle shifts will firm up also, which you don't want.

Originally Posted by AlexTheSeal

OK... how do I know that they are not plugged and/or leaking? Apply vacuum with the MityVac to the vacuum inputs on the one? See if the other passes pressure through when energized or vice versa? I'm at a loss. Do they act more like relays (on/off) or more like transistors (sensitive to variable voltage or resistance?

Basically you need to blow through each tube and make sure it's clear. Or just replace every single one... the old Tecalan tubes get brittle with heat, and they're cheap. You can replace everything with fresh tubing for about $20, it's a few bucks per meter.

The switchover valves are basically relays, they are on or off. A plunger inside moves up & down. I believe the center port is routed to the bottom with no voltage, and routed to the top with voltage applied. You should be able to easily blow through them. If they're plugged, they can be very hard to clean out, they can't be taken apart. Usually the only one that gets clogged is the one between the manifold and the ALDA, it can get plugged with oily sooty goop from the intake.

[AlexTheSeal]

Originally Posted by gsxr

Try a half-turn at a time. "Slight" is one or two notches. If you go too firm at WOT, all the part throttle shifts will firm up also, which you don't want.

OK. Clockwise hardens the shifts, right?

Basically you need to blow through each tube and make sure it's clear. Or just replace every single one... the old Tecalan tubes get brittle with heat, and they're cheap. You can replace everything with fresh tubing for about $20, it's a few bucks per meter.

All the hard lines hold vacuum just fine, so I'm going to be cheap and not replace them quite yet (at least not until I have Rusty on the phone again so I can order the right colors). What I was worried about was more the switchover valves...

The switchover valves are basically relays, they are on or off. A plunger inside moves up & down. I believe the center port is routed to the bottom with no voltage, and routed to the top with voltage applied. You should be able to easily blow through them. If they're plugged, they can be very hard to clean out, they can't be taken apart. Usually the only one that gets clogged is the one between the manifold and the ALDA, it can get plugged with oily sooty goop from the intake.

OK, that gives me enough to play around and see if they are functional and/or leaking. That's what I have a Mity-Vac and a bench power supply for, after all. I'll post my detailed findings on their operation, if it'll help anyone. I'm still concerned about the fact that my BFS takes so long to come up to full vacuum at idle, but I don't have any other symptoms of a leak in the vac system (intermittent climate control, slow rear headrests, etc.).

[aersloat]

Dave

My plumbing doesn't look like anything like the other 603s I have seen. I am curious how things can be cleaned up similar to what you did. I have mapped out what is going on and taken a picture. I have three switchovers - two right next to the BFS. My cruise doesn't work and I have removed my EGR and all the plumbing over under the air filter. My ALDA has been turned about 1.75 turns CCW and I cleaned out the intake nipple and SO. I recently replaced my neutral safety switch and shift bushings.

I get no flaring at WOT and but some, mostly 2-3, under normal throttle. Before I did the ALDA, NSS, bushings, EGR, and fluid/filter, I would get very hard shifts. I haven't tried to manually adjust anything for shifting. I also haven't put a gauge on anything. I must admit that I am hesitant to just start removing things as I don't have a very good handle on which part is doing what. Thanks.

[Brian Carlton]

Originally Posted by AlexTheSeal

I'm still concerned about the fact that my BFS takes so long to come up to full vacuum at idle, but I don't have any other symptoms of a leak in the vac system (intermittent climate control, slow rear headrests, etc.).

Check two things for this:

1) The vacuum amplifier (BFS) has an input from the vacuum pump. Measure the vacuum at this line to be sure you have full pump vacuum (above 20").

2) The amplifier also has an input from the VCV. T into this line and run the gauge to the cabin and drive the vehicle. See if you get a quick 15" from the VCV at idle and the delay in vacuum rise is eliminated. If so, then you've confirmed that the culprit is the amplifier.

[DonBaker]

I'd like to tap into this thread since I'm frustrated with diagnosing my transmission as well. I've got a 91 350SD with what I think is the 722.361 transmission. I'm trying to interpret the PDF that is mentioned above for setting the VCV. I've read this before and it didn't make sense to me then either.. :>)

As way of my question, let me interpret what I think it says: First you connect your vacuum tester to the damper ( the line coming out of the bottom?) and take a reading at idle speed. Mine should be 385 mbars.

Then "when engine is switched off, move accelerator control to full-load stop. Specification: 0 millibars".

Huh? You shut engine off, move the accelerator to stop and you should get 0 millibars? Sure you should, you just shut off your vacuum?

Then to set the VCV, you "slacken fastening bolts, run at full throttle until control lever of injection pump is resting at full-load stop. Turn VCV in direction of arrow (right) until a resistance is felt. Tighten.." This isn't suggesting you throttle up to full power and fiddle with setting this, right? Is this really done with the engine off?

They way you set the earlier VCV valves is with a gauge and adjusting the spread, say around 12 in hg down to 0 at full throttle. Please help me out here, what am I supposed to be doing with this thing?

Don