Apologies-yet another vacuum question...

[lbj.lbj]

I hate that I'm posting yet another one of these when so many exist. I've been going through the archives, I've looked at several vacuum diagrams for an 82 300d and none match and my brain is just fried from parting one car, swapping interiors, and trying to fix this one. Please help.
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I was degreasing my engine to hunt for an oil leak and I have disconnected SOMETHING and now my transmission is a disaster. It drove perfectly, and now its flaring, clunking, and a total mess.

I'm sure I've made it far worse reconfiguring lines according to diagrams, and then undoing when it didn't help


Attached is a photo of things that are...clearly wrong.



I'm not sure what broke off of the line to the booster where the hard white remnant is, I'm comparing it with my other 82 300d and that just made a bigger mess.

I have plenty of spare lines and branches from the car I'm parting out, even just an actual photo of a correctly configured system in someones car would be a huge help.

Could someone help me here? the system was holding pressure fine, and
I don't have my mighty vac here, I'm stuck and frustrated.

Many thanks as always,

LBJ

[Jarod]

This is going to be complicated. I modified your pic to possibly help but looking at it, it looks confusing, and I'm not 100% sure its correct.

The issue you have is you've got vacuum on both sides of the vac modulator, the brown hose going to the bottom of it should not be there, that should be a black hose that vents to atmosphere.

B that has the splitter and yellow hoses is for the central locking.

The 4 way splitter that has C on it should connect D, B, The green one currently on the 4 way C as well as the brown one going directly above C to the bottom of the transmission vacuum modulator.

Where the brown one on the vacuum modulator was should be connected to a black one that appears to be dangling near C (or it may not exist at all, thats a vacuum bleed essentially, it disappears into the firewall but is open to atmosphere)

A should be connected to the 3 way that was connected to the 4 way as part of C.

Maybe that makes some semblance of sense? maybe someone else can chime in to correct whatever mistake I've made in the pseudo-diagram

[lbj.lbj]

thank you so much, the diagram does help, as always, very appreciated.

the plot thickens- I disconnected the line to the trans and teed off the source and got hard shifts, but consistent, and not lurching. I crawled under and the line had come off the modulator at some point during this debacle so there was no vac to the transmission.


Added a new connector there, hooked it back up, drove it again and it just feels strange, I take my foot off the accelerator and theres a long lag before I feel it disengage. very odd feeling the car 'run' while coasting downhill.

I'm guessing I can chalk this up to the vacuum mess I have going on (besides the line from the control valve to the modulator, which is firmly connected) but I do want to check the pressure asap, going to run out for a new mity tomorrow once I re-route as I have NO idea how old the modulator is on this car.


Jarod, I just want to clarify, you're talking about the vac control valve and dampener here right?

Originally Posted by Jarod

The issue you have is you've got vacuum on both sides of the vac modulator, the brown hose going to the bottom of it should not be there, that should be a black hose that vents to atmosphere.

B that has the splitter and yellow hoses is for the central locking.

The 4 way splitter that has C on it should connect D, B, The green one currently on the 4 way C as well as the brown one going directly above C to the bottom of the transmission vacuum modulator.

Where the brown one on the vacuum modulator was should be connected to a black one that appears to be dangling near C (or it may not exist at all, thats a vacuum bleed essentially, it disappears into the firewall but is open to atmosphere)

A should be connected to the 3 way that was connected to the 4 way as part of C.

[tyl604]

LBJ - if you had the line to the vac modulator disconnected, you should get very good upshifts and it should only clunk on the downshift. The VCV is designed to bleed off vac to your tranny as soon as you hit the throttle which mimics a gas engine.

If you are getting hard upshifts with that line disconnected from the tranny, you need to adjust or replace the vac modulator.

[lbj.lbj]

Following up—

I’ve attached a pic of the changes I’ve made.



My ignition key doesn’t match the doors at the moment, so if I eliminate the locking system by teeing off everything flagged in white, would my setup be somewhat correct?

(EDIT- it wasn't correct, I didn't have shutoff until I connected the two ends in my had tagged in white)

The line you mentioned in the thread that looked like it’s dangling runs to the oil filter, I don’t have a black vac line running into the cabin.

The circled open arm on the 3 way splitter is where the black bleed line would be?

Looking at two cars from the same year and how wildly different the vac setup is between them (and from ANY diagrams) is...fun.

Originally Posted by Jarod

This is going to be complicated. I modified your pic to possibly help but looking at it, it looks confusing, and I'm not 100% sure its correct.

The issue you have is you've got vacuum on both sides of the vac modulator, the brown hose going to the bottom of it should not be there, that should be a black hose that vents to atmosphere.

B that has the splitter and yellow hoses is for the central locking.

The 4 way splitter that has C on it should connect D, B, The green one currently on the 4 way C as well as the brown one going directly above C to the bottom of the transmission vacuum modulator.

Where the brown one on the vacuum modulator was should be connected to a black one that appears to be dangling near C (or it may not exist at all, thats a vacuum bleed essentially, it disappears into the firewall but is open to atmosphere)

A should be connected to the 3 way that was connected to the 4 way as part of C.

Maybe that makes some semblance of sense? maybe someone else can chime in to correct whatever mistake I've made in the pseudo-diagram

[Jarod]

Based on what I can see on the new photo it does look correct, the underlined white taped ones are for vac locking to the best of my knowledge, it may be possible that one of the lines on that circuit is responsible for the shutdown pod.

EDIT: Yes, I believe the circled tee outlet should be the "vent" which was normally a black line that ran into the cabin/firewall somewhere and just vented excess vacuum

How is your transmission shifting now?

The vacuum modulator/vcv/whatever its called is supposed to hold a certain amount of vacuum and as throttle is increased it should drop the gauge back to 0 or at least lower than it started.

Somewhere I have the specs for it, if I locate them I'll post them as well, as getting the transmission shifting nicely makes a world of difference in how the car feels

I'll go take some pics of both of my cars tomorrow, which are both 82 300d models, one is automatic and fairly untouched in terms of the vac system, the other grey car no longer has the automatic trans, so it is a bit different, but some of the stuff is still there because I didn't bother removing it when I swapped in the 4 speed.

[tyl604]

The vcv should be set to produce about 12-15 inHg. When you hit the throttle it goes back to zero very quickly. You need vac for downshifts only. Because it bleeds to zero with throttle, it is readily apparent that upshifts use no vac.

[lbj.lbj]

Thank you both VERY much for your help.

I’m just going to buy a spare mity at this point. Left Brooklyn because of pandemic and ended up in VT temporarily with limited tools so of course I’m doing a full interior swap and part out because I found a great part out/interior car up here. Lord help me.

Will update on how she’s shifting once I put a drivers seat back in today..

[lbj.lbj]

So I just took her out, with AND without the vac line to the trans connected its not driving well, just... different kinds of not well with and without the line to the modulator attached.

Amount of flaring varied, but overheated within 10 min either way ( I'm in the mountains so I have a huge uphill either way I go)

Not getting 4th with the vac line to the transmission attached.

Everything was fine until I knocked things loose degreasing and now it's essentially undriveable, if I didn't know better I would think my trans was toast, its that bad.

I'm going to get under and see if the line has come loose from the mod again...

Jarod-Looking forward to the pics of your setup, hoping it helps me sort this all out.

[tyl604]

Ok - going back to your original post, you said you knocked something off and the tranny is clunking and flaring. The clunking is obviously during downshifts because it needs vac; you knocked the line off the vac modulator. Hook it back up and that should go away.
tun
Was it flaring before you started the degreasing? I would guess that it was. You can try adjusting the vac modulator a bit to give crisper upshifts; turning the dial CW gives crisper upshifts.

However the flaring could be the result of a bad K-1 valve or maybe the B2? I forget. I will look for the chart and post it. You need to know exactly when it is flaring and then match that with the chart; this will possibly tell you what needs to be replaced to stop the flaring. Will look now.

Here it is:

Moderator - maybe make this a Sticky?

This Peachparts Wiki is great and could tell you all you need to know:
http://www.peachparts.com/Wikka/TransVacTune


Read this thread too. Kerry notes that too much vac will create a flare; news to me. Together these two should help.

[lbj.lbj]

TYL604-

I wasn’t having any flaring at all before this whole mess. I’ve had the 1st/2nd reverse b2 issue before and it doesn’t feel like that..k1 I don’t have any experience with.

As it stands, I don’t have 4th gear...

Thanks so much for your help, I’m going to order a new mod as well, it can’t hurt...

[tyl604]

No flaring? Interesting. Not sure what to recommend other than a study of the Peachparts Wiki.

[Jarod]

In my experience too much vacuum to the transmission causes flaring, no vacuum causes rubber burning shifts.

When I knocked the trans vacuum line off on my 1980 300SD it drifted corners when the 1-2 shift hit (factory LSD I believe, either way it broke both tires loose with ease when that hose was off, I'm sure that was not great for the flex disc guibo things nor the rest of the drivetrain)

The easiest way I can relate it is the vacuum to our trans is like 1/2 of what the TV does on chrysler transmissions. the other 1/2 of that is the bowden cable.

The vacuum controls the line pressure which dictates how harsh or soft shifts are, and the bowden cable varies the shift timing based on the "detected load" determined from the throttle position.

I'd check to see that the vacuum is diminishing properly with throttle movement on the line going to the transmission. I'd disconnect part of the throttle linkage so you can move the arm on the modulator valve thingy without revving the engine to the moon

Some light reading: It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ...


Gotta go snap some pics quick, I'll post those momentarily

[Jarod]

Ok, here is some photos of my vacuum stuff.

Although it appears there was a horrible theft that resulted in some EGR related hoses vanishing while I wasn't looking.

So the front outlet on the brake booster hose goes through a little teeny tiny oriface (seen inbetween the Y/T connector that goes to the green thing on the top of the VCV valvey thingy and the supply from the brake booster line)

I suspect that oriface might be what you're missing. you have a little fuel filter thing in there as a coupler where there should be one of those orifaces.
Its visible the best in the 2nd picture just above my pointer finger. teeny little yellowish looking goober.

Here is a quote from that thread I linked moments ago:
"It appears that my “T” that branches off from the main pump-to-booster vacuum line had been replaced and no longer had its 1st stage of restricted orifice"

everything else looks the same to me, but not having that oriface would provide excess vacuum to the VCV which would make your transmission shift very soft.

EDIT: Oops, holdon, I see the little restriction thingy in one of the pics, its inbetween your two tee/Y things that one goes to the EGR stuff and the supply.

[tyl604]

Jarod - excess vac causes the upshift to be hard, not soft. The vcv is designed to bleed off vac when you hit the throttle. More throttle means less vac. When you hit the throttle, vac almost instantly goes down to zero to give smooth upshifts. You get clunky downshifts (not upshifts) with no vac.