It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ... - Page 14 - PeachParts Mercedes-Benz Forum

Brian Carlton · #**196** 12-16-2006, 04:04 PM

Quote:

Originally Posted by Samuel M. Ross

IF YES to the above, then take a healthy 3 full turn to the right on the modulator "T" key adjuster. [/B]

Adjusting the modulator to the right (clockwise) will increase modulator pressure.........AFAIK.

Samuel M. Ross · #**197** 12-16-2006, 05:46 PM

Quote:

Originally Posted by Samuel M. Ross

DD - Don't give up after coming so far.
Clarify how the tranny is shifting when you drive... is it shifting quickly from 1-to-2-to-3... and 4th gears?
IF YES to the above, then take a healthy 3 full turn[s] to the right on the modulator "T" key adjuster.
Regards,

Above is the full text of what I said... maybe I should have said "softly" AND quickly.
What the heck does "AFAIK" mean anyway Brian ?
Keep talking to us " DD " so we will know for sure what's happening!
Regards,

Brian Carlton · #**198** 12-16-2006, 06:23 PM

Quote:

Originally Posted by Samuel M. Ross

Above is the full text of what I said... maybe I should have said "softly" AND quickly.
What the heck does "AFAIK" mean anyway Brian ?
Keep talking to us " DD " so we will know for sure what's happening!
Regards,

AFAIK: "as far as I know"

If the modulator is turned clockwise, the pressure will increase, as far as I know..........this would cause the shifts to get intolerably harsh.

Samuel M. Ross · #**199** 12-16-2006, 07:16 PM

Quote:

Originally Posted by dieseldan44

the saga contnues...
i swapped out my modulator last night and went for a test drive today. i am very sorry to say it made no appreaciable difference...
Please advise... dd

... yes, I made a concerted effort to find what your shifting symptoms were DD... so would your repeat them so I can advise how you might want to adjust the mid-range setting on your modulator!
Regards,

dieseldan44 · #**200** 12-17-2006, 12:41 AM

Here's a detailed description of whats going on:

-all shifts are somewhat late. they seem to be inconsistent, somewhere between 2500-4000. i know i need to make a bowdern cable adjustment here.
-1/2 is the harshest. shifts strongly into gear, car pops forward.
-2/3 is harh, less harsh than 1/2
-3/4 is harsh, but a little better than 2/3. maybe its better just because the car is moving faster.
-downshifts are similar to the upshifts of the same gears
-shifting into gear while stopped car noticeable hard shifts into gear. going into reverse the car 'snaps' to attention, the back end lifts up a couple inches noticeably. could this be due to slop somewhere else in the drive train?
-all of these symptoms seem a little inconsistent. because the car needs other work i have been relucant to cruise around anymore than necessary in fear of making something else work. therefore, i dont have a ton of time behind the wheel wiith the problems happening.

The part of this that's troubling to me is that these symptoms haven't changed through all of the vacuum fixes. especially now that I *know* that at least some vacuum system signal is being correctly delivered to the vavle body.

My next step is to adjust the bowden cable and modulator again and just seem if theres a difference. should I adjust the modulator or VCV first?

what task am i looking at if the vacuum signal reciever in the valve body is not working? i'd imagine that since the transmission is shifting strongly that I am not in rebuild territory....but first things first, i havent given up on this.

Brian and Sam, thanks again for all of your help. what kind of data can I give you guys that would be helpful? would a movie of driving and looking at the tach be helpful?

thanks again,
dd

Samuel M. Ross · #**201** 12-17-2006, 01:12 AM

nursing a bad back so let me get back to ya tomorrow a.m. I thought your car had the more traditional soft/early shifts... but there are some ideas roaming around in my head that MIGHT help. Just a thought... a GOOD dealer man can take the tranny's S/N and compare it to the VIN and tell you IF it is original to the car! How many miles to you think the car has?
Regards,

dieseldan44 · #**202** 12-17-2006, 09:48 AM

the car has a legit 206k miles. the trans does look newer. in fact it looks downright new sitting under there. ill find out from my dealer Monday. where's the serial # under there? i havent seen it yet in my undercar travels...

Sam, sorry to hear about your back...

dd

Samuel M. Ross · #**203** 12-17-2006, 10:51 AM

Quote:

Originally Posted by dieseldan44

the car has a legit 206k miles. the trans does look newer. in fact it looks downright new sitting under there. ill find out from my dealer Monday. where's the serial # under there? i havent seen it yet in my undercar travels... dd

On our 1980(s) models the # are on the right side [looking forward]... just above the tranny pan... along the edge of the case of the transmission.
There are typically two #(s) E.g. - 1232703201... & 722.118.02.098161. I think the last of these includes a S/N where the 1st is the MBz P/N.
I still intend to go over your previous POST and get back to ya. I'm thinking that you need to turn the modulator adjuster " key " to the left but wait until I can examine you POST.
Regards,

Samuel M. Ross · #**204** 12-17-2006, 01:46 PM

WELL……….. you sure have a lot running through your mind about this project!!!... maybe too much? Let’s see if we can sort things out a bit… one thing at a time !

You had a lot in the POST below so I have edited it and put my comments [in RED] inside the quote box so it’s easier for you and others to follow along with my thoughts without going back-and-forth!

Quote:

Originally Posted by dieseldan44

Here's a detailed description of what’s going on:

[a] - all shifts are somewhat late. they seem to be inconsistent, somewhere between 2500-4000. [I’m taking this to mean hard shifting ]
[b] i know i need to make a bowden cable adjustment here.
[I have absolutely NO experience with Bowden cables… but IF we trust what is said in this POST: 1992 w124 Vacuum Control Valve Operation “The Bowden cable only controls shift points (speed/RPM), not shift firmness.” ... maybe this does need to be done. Let’s see IF Brian will make comment on this.
[c] - 1/2 is the harshest. shifts strongly into gear, car pops forward.
[ Well my first inclination is to ask you to make sure you have a functioning green “ dashpot ” chamber installed on the top of the VCV to reduce “surge” which is typically worst for the ½ shift. I have added these to both of our 1980 models for this reason. Vacuum test the chamber to make sure it does not have a crack. If you do find a crack somewhere airplane glue should fix it. ]
…. -2/3 is harsh, less harsh than 1/2
…..-3/4 is harsh, but a little better than 2/3.
……maybe its better just because the car is moving faster.
[d] - downshifts are similar to the up-shifts of the same gears
[e] -shifting into gear while stopped car noticeable hard shifts into gear. going into reverse the car 'snaps' to attention, the back end lifts up a couple inches noticeably. could this be due to slop somewhere else in the drive train?
[f] -all of these symptoms seem a little inconsistent. because the car needs other work i have been reluctant to cruise around anymore than necessary in fear of making something else work. therefore, i dont have a ton of time behind the wheel with the problems happening.
[ In response to ALL the above, I would take a healthy 3 to 5 full turns TO THE LEFT on the vacuum modulator “ T / Key ” adjuster and see if this makes any noticeable difference. This is a good time to suggest a diagnostic step that I used that is somewhat similar to what Brian has related… namely after make a 5-turn to left adjustment you drive the car with all the vacuum control system hooked up… note how the tranny shifts… and immediately disconnect the vacuum line to the modulator (in engine compartment) and note how the tranny shifts again – report back the results) ]

The part of this that's troubling to me is that these symptoms haven't changed through all of the vacuum fixes. especially now that I *know* that at least some vacuum system signal is being correctly delivered to the vavle body. My next step is to adjust the bowden cable and modulator again and just see if there’s a difference.
[ I canNOT help you with this but I know there are tons of POSTs on the FORUM to help you and IF my back allows will do some research to see what I can come up with !]
[g] should I adjust the modulator or VCV first?
[ I think it is safe to say the VCV is at least close to the proper setting… so lets work with your new modulator for now ]
[h] what task am i looking at if the vacuum signal receiver in the valve body is not working? [ not sure what that component is… let’s not go there yet ]

[i] i'd imagine that since the transmission is shifting strongly that I am not in rebuild territory [ I agree ] … but first things first, i havent given up on this.

Brian and Sam, thanks again for all of your help. what kind of data can I give you guys that would be helpful? would a movie of driving and looking at the tach be helpful?
thanks again,
dd

Merry Christmas Dan !,

H-townbenzoboy · #**205** 12-17-2006, 04:48 PM

Well, I need to update you guys on my problem. As you may remember, I had a VCV that would not hold any sort of vacuum whatsoever. Not wanting to spend over $200 on a new one, I was able to find a good, used one on eBay. I installed it, and my shifts are nice and smooth, no more head jerking! I just need to make some throttle linkage adjustments to make everything perfect.

dan_the_welder · #**206** 12-17-2006, 05:27 PM

Hey dieseldan44, check this.

This may sound obvious, but I did a big vacuum clean up on my girl's 82 300D and the shifting got worse.

Modulator time right? So I get down under there and the hose is not ever connected!

I guess I pulled it off accidentally while working on something else.

So I replaced the greasy messed up piece of rubber vac hose and voilla, gooder shiftin'

Samuel M. Ross · #**207** 12-17-2006, 06:34 PM

Quote:

Originally Posted by H-townbenzoboy

Well, I need to update you guys on my problem. As you may remember, I had a VCV that would not hold any sort of vacuum whatsoever. Not wanting to spend over $200 on a new one, I was able to find a good, used one on eBay. I installed it, and my shifts are nice and smooth, no more head jerking! I just need to make some throttle linkage adjustments to make everything perfect.

H-TownBenzOboy... what did you pay on E-bay for your VCV?
Regards,

dieseldan44 · #**208** 12-17-2006, 06:58 PM

dan - thank you for the tip - i will make sure again my modulator is holding vacuum and that i havent yanked the vac line off of it.

htownbenzboy - im envious of your fix, congrats!

sam - youre right, lot is running through my mind on this. the car has a lot of issues, all of which i think can be resolved, but the trans is the biggest one and i want to get it figured out before i invest further.

ill follow the adivce given here and report back, probably tomorrow night. in the meantime ill do a little more reasearch on valve body.

H-townbenzoboy · #**209** 12-17-2006, 07:25 PM

Quote:

Originally Posted by Samuel M. Ross

H-TownBenzOboy... what did you pay on E-bay for your VCV?
Regards,

About $36.

Samuel M. Ross · #**210** 12-17-2006, 07:48 PM

Quote:

Originally Posted by dieseldan44

... the car has a lot of issues... but the trans[mission] is the biggest one and i want to get it figured out before i invested further...

Entirely understandable. Before I invested ~$2,500 in the rebuilt tranny in my Son's 1980 300D, I also felt I had to first get the engine running right and thus serve as a measure of proof that the car was worth that investment. In my case all it took to get the engine running dramatically better was to effectively reinstall the " BB " in the vacuum line line to the EGR!

I've read that it's not unusual for these tranny(s) fail starting at ~250K so knowing that our 300D's tranny had 300K made my decision to go ahead on the investment a bit easier... but when the MB trained [in trannies] mechanic couldn't even get the rebuilt set up and running right, well that's when I decided I had to learn about these Engine/Tranny/EGR vacuum control systems!!
Regards,