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  #1  
Old 04-06-2009, 05:33 PM
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Switchover valve and VCV testing

I recently removed the EGR and ARV controls from my car as Brian Carlton instructed. The car runs much, much better.

I was also wondering if the switchover valve on the firewall next to the Alda switchover valve is really necessary? It looks like in the vacuum diagram that the switchover valve lines just make a loop. Then one of the wires goes over to a sensor mounted in the thermostat housing.

I have plugged my A/C vacuum lines and Door lock lines to begin vacuum troubleshooting under the hood.

I'm trying to get my transmission tip top for daily driving. I am expieriencing the common 2/3 shift flare.

In regards to testing the vacuum going to the VCV, do I pull the line off the top of the VCV and read the vacuum there? Or do I get a reading from the VCV a different way.

I'm trying to decide if I should try to adjust the bottom of the blue flying saucer or install a spring kit to correct the problem. I read somewhere that it was possible to adjust the flying saucer. But that adjustment is dependent on the vacuum reading at the VCV correct?

Any help in this area is greatly appreciated.
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Old 04-06-2009, 05:55 PM
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If you have a Mityvac, you should first check the vauum from the VCV to the transmission before you adjust the flying saucer on the trans.

It should read 12-15" at idle, and drop to 0 with full throttle.
If you're flaring, maybe adjust the VCV output to 11-12 at idle.
If you're still flaring, you can try adjusting the flying saucer clockwise to firm up the shifts. You can check if it's still working by seeing if it actually holds vacuum. If not, time to replace.
If you've done all this and still see flaring in the 2-3, time for the K1 kit.

The overboost protection valve going to the ALDA has nothing to do with the vacuum system to the trans. It can be bypassed, but you should just replace it if it doesn't work. What it will affect is your boost performance. First clean the banjo bolt and lines going from the manifold to the overboost protection valve, then the line to the ALDA. If it was clogged, you will see an increase in takeoff power.
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Old 04-06-2009, 06:35 PM
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Thanks a bunch! I'll get the readings and post the results tomorrow afternoon.

Using the mighty vac... Do I just "T" into the line after the dash pot going to the VCV for the reading? Assuming the same for the line to the trans? What should those readings be?

The Alda system is fine. Lines are all clean, etc... That is not the "switchover valve" I am referring to. There is another "switchover valve" on the firewall about 5 inches away from the one that controls the Alda. This valve forms a loop in the vacuum system and has a wire running over to a sensor in the thermostat housing. In the diagram below, in the upper left corner, valve #125 is the valve I am referring to. The wire goes to sensor #20.

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Old 04-06-2009, 07:55 PM
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Quote:
Originally Posted by snookwhaler View Post
I'm trying to get my transmission tip top for daily driving. I am expieriencing the common 2/3 shift flare.

In regards to testing the vacuum going to the VCV, do I pull the line off the top of the VCV and read the vacuum there? Or do I get a reading from the VCV a different way.

I'm trying to decide if I should try to adjust the bottom of the blue flying saucer or install a spring kit to correct the problem. I read somewhere that it was possible to adjust the flying saucer. But that adjustment is dependent on the vacuum reading at the VCV correct?

Any help in this area is greatly appreciated.
The '85 has a very unique setup and it's responses are totally different than any other combination. So, you've got to be very careful with any advice that you get........unless the member has the exact same vehicle.

I don't have that vehicle, but I did recommend that one member make a small adjustment to the amplifier (blue flying saucer). Under the device you'll find a plastic cover. Remove the cover and there will be a 4mm plastic adjustment screw. Turn the screw clockwise by two turns and put the amplifier back into the vehicle. Take it for a drive and see if the 2-3 flare is reduced. This attempt may work........may not.......but it won't harm anything to try it.
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Old 04-06-2009, 08:00 PM
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Quote:
Originally Posted by snookwhaler View Post
I was also wondering if the switchover valve on the firewall next to the Alda switchover valve is really necessary? It looks like in the vacuum diagram that the switchover valve lines just make a loop. Then one of the wires goes over to a sensor mounted in the thermostat housing.
That switchover valve is used to soften the shifts when cold. If the shifts are acceptable when cold, you can eliminate it if you wish.
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Old 04-06-2009, 08:13 PM
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Thanks Brian. I was hoping you would chime in.

I read the post about the 2/3 flare and your mention of adjusting the saucer to fix it. I did not want to hijack that post, so I did not chime in.

I guess the big question is do I need to have "X" vacuum at the VCV to be able to adjust the saucer safely or does it even matter?

I pulled vacuum on the line going down to the modulator before the storms came. That line and the VCV were good (with the mighty vac). They both hold vacuum. It is almost like the switchover valve is causing a leak?

I don't know? I'll get some readings, adjust that saucer and post the resusts.

Thanks,

AJ
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Old 04-06-2009, 08:26 PM
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Quote:
Originally Posted by snookwhaler View Post
Thanks Brian. I was hoping you would chime in.

I read the post about the 2/3 flare and your mention of adjusting the saucer to fix it. I did not want to hijack that post, so I did not chime in.

I guess the big question is do I need to have "X" vacuum at the VCV to be able to adjust the saucer safely or does it even matter?

I pulled vacuum on the line going down to the modulator before the storms came. That line and the VCV were good (with the mighty vac). They both hold vacuum. It is almost like the switchover valve is causing a leak?

I don't know? I'll get some readings, adjust that saucer and post the resusts.

Thanks,

AJ
You can adjust the amplifier independently of the VCV. On that system, the VCV doesn't affect the final result as it would typically on the older vehicles.

See what the amplifier does........if it doesn't do what you want.......then we'll see what we can do with the VCV.
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Old 04-06-2009, 08:41 PM
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Nice thread thanks, as far as the thrust pin or k1 spring i wouldnt hessitate to change it, the new one is beefier and for 5-7 dollars its nto a bad buy in your way to trouble shoot the system, i have seen many a diesel benefit from a k1 spring.
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Old 04-06-2009, 09:03 PM
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Thanks for that. Is it the K1 or K2 spring? I have read about both springs in the search. I wish I would have known about this a few weeks ago. I have already drained and changed the trans. oil and filter. I can drain the pan again to do it. I just wish I would have known. It sounds pretty simple to change.

I spend more time searching and reading old threads more than I read the new ones. It all kind of runs together after a while.
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Old 04-06-2009, 10:41 PM
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You will not need to drain the TC nor change the filter, but you will lose the 3-4qts in the pan.

I don't know if the gasket being new, will stand one R&R, haven't tried that one. However, the K1 spring is a simple job: P/N 126 270 44 77
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  #11  
Old 04-07-2009, 03:45 PM
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Readings

Ok... Here is what I got for readings.

I disconnected the vacuum line at the top of the VCV and "T'd" into that line between the dashpot and the top of the VCV. The reading there is 12.5 in. at idle and drops rapidly when the throttle is pressed. I also pulled vacuum with the mighty vac on the VCV. It holds vacuum.

I also disconnected the line running from the flying saucer down to the modulator and got 13 in. at idle. Pushing the throttle gave some drop but much slower than over at the VCV. I also pulled vacuum on the line going to the modulator. It holds vacuum.

I guess my next step is to disconnect the 50 degree switchover valve and eliminate it from the system to see if the shifts improve? Then adjust the bottom of the saucer if that fails? I'm guessing here.
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Old 04-07-2009, 03:57 PM
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snook,

I recently went through a similar debug on my 85 and I think I have a pretty good handle on the workings of the system. When I took my EGR switchover valve and ARV valve out, I had flaring too. The ARV valve leaked badly, and a past tech must have adjusted the VCV to compensate for it. It shifted great WITH the leaky valve. Once that valve was gone - flaring. I was at about 13 mmHG when I was getting the flaring. I went down to about 8 mmHG at idle by VCV adjustment and the car shifts wonderfully.

*Your next step is to adjust the VCV to give you less vacuum at idle* You need an 8mm little wrench. There is a plastic cap on the VCV itself, its small and points to the driver's side shock tower. Pull that off, you will see a brass adjustment piece with 8mm flats. T your gauge into the line that dives down to the vacuum modulator (the black line that goes down behind the engine to the transmission area). Start the car. You will read something on the gauge. Turn the brass adjustment piece clockwise for more vacuum, counter clockwise for less. You will want LESS. You will probably need about a 1/4 turn to get down to the 8 mmHg range. (tip: hold the rack while you are making adjustments, or it will want to rev the engine - youll see what I mean) Set it there, remove the gauge, go for a drive and see where you are at. You can make micro adjustments one way or another without the gauge if you need to fine tune.

Its far easier to adjust the VCV than the blue flying saucer. Go that route. Try to remove the saucer to get at the adjustment and you'll see what I mean.

The top switchover valve behind the brake booster is a temp switch to allow for softer shifting when the engine is cold. Its a nice feature. My 82 shifts more harshly when cold. The 85 definitely adjusts accordingly and it's nice - don't eliminate that feature unless you can find a fault.

Hands off the spring kit till you have exhausted the possibilities here This process is so delightfully easier.

dd
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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
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'83 300TD Cali Wagon 210k, wife's car

Last edited by dieseldan44; 04-07-2009 at 04:13 PM.
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  #13  
Old 04-07-2009, 04:41 PM
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DD,

Thanks a bunch! I already adjusted the saucer and went for a drive before I read your post. Doing 2 turns as Brian suggested would not go. 1 1/4 turns was all the way in. So, I left it at 3/4 turn and went for a drive. The transmission is not flaring like it used to and I would call it fixed, BUT the power has noticeably dropped off? It looks like one of the lines from the saucer also goes to the Alda. Have I somehow cut the signal to the Alda by adjusting the saucer?

I think I may go put the saucer back to the old setting and try what you have suggested. Is there a specification for vacuum at the VCV or do I just need to adjust it by feel?

Also, if I adjust the vacuum at the VCV, do I need to adjust anything on the IP? You mentioned the rack. Just curious.

Thanks,

AJ
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Old 04-07-2009, 05:27 PM
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AJ,

I don't understand how the blue saucer interacts with the boost signal - but - maybe its leaking boost somehow? Maybe the hose that carried the boost signal from the ALDA got cracked and is leaking since you moved?

I think the saucer just senses the boost level to adjust shifting.

Id do what you are already thinking of - put the saucer back and make your adjustments from the VCV. I think you'll be all set after that.

dd
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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car
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  #15  
Old 04-07-2009, 05:48 PM
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DD,

That worked like a champ. I removed the saucer, put it back at its original position, adjusted the VCV down to about 9.5 and it shifts smooth now. It shifts so smooth that the first couples shifts are almost undetectable unless your foot is on the floor. Now, when I floor it, the shifts are firm and precise. No flaring at all. I did get back a bit of a clunk in the rear. But I think that is related to a different issue I am working on in couple days (replacing the rear diff. mount). I adjusted the trans. Bowden cable so the shifts are mostly between 2500 to 3000 with moderate pedal pressure... WOT puts the 1/2 shift around 3,800 RPM, the 2/3 shift around 4500 RPM and the 3/4 shift around 4500 RPM.

Works great!

Thanks!

AJ
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