Transmission Questions
 

First of all, I have been able to hear a slight whistle from under the car (assuming the trans) when I have the car in reverse. It's very subtle, and is there only about 1/2 the time, and it's not loud. I can only hear it when I'm next to an object to bounce the sound. Nothing in archives regarding.

Also, I want to know what variants there are that can adversely affect the operation of a transmission, given the transmission itself is still good and in no need of a rebuild. I ask this because I *think* my transmission shifts weird under hard acceleration from 2nd to 3rd and somewhat from 3rd to 4th. This symptom may be psychological, because no one else notices it in any way. And it obviously can't be major due to it's lack of apparantness. It seems as though it "flares" ever so lightly between these 2 gear changes. But I thought flaring would be the other way around? When accelerate slowly, everythings seems fine, but when I accelerate hard, it "seems" as though the shift takes a little longer. I hope this makes sense... to my question: What can I check? Aren't there vacuum lines that can affect this? Do I have an adjustment (bowden?)? Everything else is absolutely fine with the trans otherwise. I just had new fluid and filter put in (last one done 15k miles ago, better safe than sorry since I drive the **** out of my poor trans!). Also, I Fletcher Jones only charges $75 for this! I was shocked... so cheap for them!

Thanks in advance for any help anyone can give.

Well on my way home from work tonight, I decided to really analyze the shifting. I made a few quick runs from 40-60, to make a 2-3 shift. I really think that the new fluid may have improved shift quality slightly. And there probably is NOTHING wrong with it... Probably just paranoid me..:eek:
But just for reassurance... could there be an ever so slight vacuum leak in one of the lines that works the trans?
Thanks again.

hey David,
so what kinda fluid did you wind up using? is that place a dealer? so did you wind up using MB Dexron III? like you said it's cheap insurance. i'm planning on switching everything, tranny and diff, to Swepco on my 300e-2.8. i hear a bit of a whine - not much but the fact that i hear something is unacceptable to me at this point with only 52k...

HEY!! Stevebfl?

:mad: :confused: :eek: ;)


Can anyone help?

JSmith,
I believe they use Dextron III (which is what is supposed to be used for 722.4 trans.) and they use Valvoline @ my dealer.
BTW, will post some pix of kickdown switch, I finally got the new one in there... a very frustrating 10 minutes!!

re: kickdown - i thought you already fixed that. did it break again? i am having my pedal / switch setup checked out by a local mech when i put the swepco diff oil in.

keep us posted.

David,

You can make some simple adjustments to suit your style and desire in shifting. Based upon your comments I would adjust your modulator clockwise three quarters turn and slightly hasten the control pressure shift point.

Thanks Steve!
I am glad to know there is such an adjustment. But where is it? Can you be specific? Thanks a bunch! I really hope it helps. Thanks again.

JSmith, No, I finally got around to fixing the kick-down. It would work, but it was just a crappy contact and it would stick.

The modulator is at the front drivers side of the trans (after the bellhousing). The adjustment is probably under a anti-tamper adjustment cap. If you could get to it there is a point which when squeezed would release the cap. In the car one will have to pop the cap with a screwdriver (possibly destroying it - have a spare).

Beneath the cap is a metal adjusting tee. Turn the tee 3/4 turn clockwise for stronger shifts.

A simpler adjustment is the control pressure cable. The cable housing has one adjustment. To make the shift earlier the cable housing will need to be adjusted shorter (the cable in effect made longer). This adjustment is a plastic, 13mm wrench size, nut at the cable attachment. By making the shift earlier it usually causes the shift to be made harder (as one doesn't tend to let up on the throttle).

David,
I just took my kickdown switch off- it was just squeeze clips and came off in 10 seconds. Then the connector was another 10 - what was the difficulty? You do have to have the seats all the way out but otherwise it was cake. Now I tested the two pairs off pins with an ohmeter. One pair was constant on and the other was constant off. I don't think this is documented in the manual but I think it is probably working. The receptacle seemed intact and it clicked right back in. I'm wondering though if the plug was stuck in wrong. Time for a test drive...

whoa, hey i think it's working now! could it have been the plug was in the wrong way? if it was possible to do that then it would make a difference since the pairs have different configs. i have to verify this new behavior tomorrow going to work.

btw, i notice that it is shifting early at 4k rpm, it should shift at redline when you have it in kickdown right? or is that symptomatic of something else?

My msg just got lost in cyberspace! GRRR.

I think i found the modulator control, but the 8mm seemed too small to adjust, and the 10mm seemed to big. I gave up after only a second or two of trying when the thing shot sparks at me! I have posted a picture, have I found the correct adjustment? The cap came off easily. Is there anything I'm doing wrong?

Also, where is the control pressure cable?

Thanks again Steve. You are great.:)

David,

You really got me. I don't know what you have pictured, but it is not the modulator.

I am enclosing a link which will show you everything you ever wanted to know about rebuilding a 722.3/4 tranny. There will be a picture of the modulator somewhere. I am having a great difficulty with my DSL line and it took me 10 minutes to get the link, so I haven't reviewed it for the actual page. You will find very nice pictures of every part of the trans.

http://www.transonline.com/electroPublisher/website/index.cfm?pageID=2877#

Ok, I had trouble with the page too.

just go to www.transonline.com, then go to TotalTech Database (on the left), then SHOW ME 'Mercedes' and then click on Oil Pressures. That's where you'll see the picture (2nd pic down i believe).
Now the only thing i'm confused on is which one do i turn 3/4 turn clockwise? The one on the left in the image? The bigger one? And the other one, which way and how much should i adjust it?
Thanks for all the help. I just cannot wait to for the improvement in shift quality!!!! :D :D :D

Ok, the pressure is the big one with the cap on it... towards the front of the car, while the modulator is the smaller one more towards the rear (the one I turn 3/4 turn clockwise), correct?

(I just want to be extra careful because I know this is risky-business!)

Also, it is a very small crevice/space to work in... so it is somewhat difficult to access? No other way around it I'm assuming.

(ONE more thing... are your (Steve) recommendations going to firm up the shifts a little bit? And this will be better for the trans when driving hard? THANKS Again.. I'm so excited... .......I JUST CAN'T FIGHT IT! Anyone know that song?!;) )


I swear, if I edit this post ONE more time.... GRRR...
JSmith,
I know... I had one hell of a time removing my kickdown switch though. Once I got my new kickdown (only $14) switch, I saw how I would take the old one out. But I couldn't get it out! I had screwdrivers trying to wedge it out, I was breaking peices of it and getting a little frustrated. One end came out, but the other would not. And the more I pulled on one end, the more the other end stuck in there. So I cut some of the carpet around the switch, and it came off pretty easy from there. But the precision of the new kickdown is really nice (firm click, constant resistance pressure).

Aww, I should have knocked on wood (burl walnut?), another addition. Now I'm confused, I think I have the 2 adjustments @ss backwards... ohhh, sorry, I've probably posted a whole bunch of unneeded crap!

Back again... It's a good thing I didn't get too far with "adjusting" whatever it was that was sparking... :eek: :eek: :eek: :p

Here is the image of the afforementioned diagram.

I really had to crop it down to make it small enough to upload...

The left adjustment (black) is the pressure adjustment?

(I'm so lost...:confused: :mad: :rolleyes: )

Why is it not showing the PICTURE!? :confused:

The modulator is the black device on the left. The pressure point is where you put the gauge to read pressures. You aren't going to need that unless you loose track of how much you are turning the mod adjustment.

BTW, the picture is of the early modulator without antitamper cap. If you look closely one can see that the adjustment key fits into castellated housing. On the new style the castellations are in the cap and nothing holds it with the cap on.

Yes the 201 and 202 chassis are a bummer to do this adjustement. Some relief can be had by lowering the rear trans support if you get in a bind.

The adjustment I am suggesting will increase mod pressure and system pressure as a result. Firmer shifts. The amount I am recommending is about two times the amount that the anti tamper cap will allow. This cap can be turned about 3/8 turn without removing it. If you can do this in the clockwise direction you might try that first. I don't think it is enough. I also would want to look into why, if you need more than 1.5 turns to suit your taste.

The link I sent should have picked out the 722.3/4 data index. Check out the part about necessary procedures for rebuilding, full of tips.

I just tried it and it does bring up the index I wanted. The search engine say Acura but ignor it unless you want a different field. The rebuild minimum (do or die) is the item I refer to above. All the items on that index refer to the 722.3/4 trans.

Thanks Steve!

I was successful in adjustin the modulator pressure. I turned it 3/4 turn clockwise and I noticed a difference, especially on hard shifts.

I broke the cap as you said I probably would, is it necessary I get a new one? No big deal, just wondering.

Also, I notice that when shifting, the next gear seems to 'catch' stronger. The release of the previous gear, ex 2 (in 2-3 shift) still seems the same. But it is MUCH better now.

Steve,
What is the other adjustment (cable?) I should make?

Thanks again!!!! :D :eek: :eek: :D :D

Yes, you should replace the cap. If it should fall off the adjusting tee will possibly fall out. The part is 126 987 07 45 and lists for $.70.

The other adjustment is where the cable attachs to the throttle linkage. Ther are a number of different arrangements but basically lengthening the cable housing in effect shortens the cable and visa versa. Shortening the cable makes shifts later. I suspect that making your shifts earlier could improve things but that depends on what happens now that the shifts are firmer. Since kick-down shift points aren't affected by this adjustment shifting earlier doesn't necessarily reduce performance.

Make your adjustments small and try things in both directions slowly (drive for a while in between to get a feel).

Thanks Steve, I know what you mean (about playing around with it).

First, what will adjusting the shift points (earlier) do?

Secondly, how do you do this?

Thanks again! :D


Was driving on the fwy home and that shift from 3-4 under hard acceleration is SO precise now! :eek: :)

Thank you so much!

steve,
i am still putting my "new" 93 300e-2.8 through its paces and as noted in my previous posts just got the kickdown switch working again. my question is about the kickdown shift points that you mention. i noticed that at lower speeds, say 30mph or so, it shifts out of 2nd at about 4k rpm while at higher speeds say 50mph or so it kicks down and heads toward redline. is this the normal pattern? where are adjustments made if possible?
this thread has been very interesting for me, thanks much!
cheers

In the kickdown position a valve is openned in the trans that dumps governor pressure (or some such). This activity superceeds the normal balance of control pressure against governor pressure on the shift valves.

When one's foot is not on the floor the shift point is determined by the control pressure mostly and somewhat by the modulator pressure. In other words shift point sare regulated by throttle position until kickdown. At kickdown the shifts are determined electrically by rpm.

i was describing the different observed behaviours with my foot to the floor and the kickdown switch activated. it appears that the upshift points are different depending on how fast you are going, at least in my car. i guess the question is whether the electronic controls take speed or other factors as input to determine shiftpoints...

Steve,
What will adjusting the shift points (earlier) do?
Secondly, how do you do this? Thanks a bunch!

JSmith,
Do you want to know all of the points where the car should switch from one gear to the next? (In kickdown and without?).
Like Steve said, the trans uses vacuum to know when to switch gears. The 722.6 was fully electronic though.

J,

I'm still not sure what you are talking about but here are the book shift points for a 124.028 car:

Full throttle 1 to 2 - 50kph

Kickdown 1 to 2 - 64kph

Full throttle 2 to 3 - 102kph

kickdown 2 to 3 - 112kph

full throttle 3 to 4 - 173kph

kickdown 3 to 4 - 180kph

All shifts from selector lever position "D"

this sort of shows what was happening. maybe i wasn't hitting the kickdown when i floored it at about 30 mph because it downshifted then upshifted at 4k rpm. when i floored it from 50 mph, it downshifted then raced towards redline , i didn't wait to see when it upshifted but it was at around 5k rpm. that's the only scenario that makes sense because otherwise it appears that it should have shifted at the same rpm/speed if i was hitting the kickdown switch....

JSmith!
Yes, that could make sense! You can floor it and engage kickdown, and then release kickdown but still be @ wide open throttle, thus you won't get the redline shift into the next gear. Plant your foot down hard and keep it there and lets see what happens.

:D i guess i better move my radar detector over from my old ride, more road testing ahead...

Quoted from SteveBFL:

"The other adjustment is where the cable attachs to the throttle linkage. Ther are a number of different arrangements but basically lengthening the cable housing in effect shortens the cable and visa versa. Shortening the cable makes shifts later. I suspect that making your shifts earlier could improve things but that depends on what happens now that the shifts are firmer. Since kick-down shift points aren't affected by this adjustment shifting earlier doesn't necessarily reduce performance.

Make your adjustments small and try things in both directions slowly (drive for a while in between to get a feel)."

Steven, I'm sorry to bring this back up, but can you be a little more specific on how I adjust this? Thanks a bunch. BTW, I love the slightly firmer shifts... really noticeable and the shifts feel much stronger when accelerating hard. Thanks again! :o :D

David,

I don't remember each cars specific adjustment. You will have to follow the cable to where it meets the throttle linkage. I think yours will have a 13mm wrench size plastic nut where the cable housing is attached. You should unscrew it to make the housing longer and the shifts later.

Since you seem to have the original problem improved I probably would suggest making the shift later. This will improve your downshifts also (allowing them at higher speeds).

Steve,

I am following this discussion closely and plan on making some similar adjustments. Is this the control pressure (Bowden?) cable you are referring too?

Thanks

Where is this adjustment Steve? Is it at the throttle linkage? TO the right of the engine block, and to the left of the washer reservoir on an M104 motor? I glanced over it and couldn't find a 13mm nut? I hate to keep asking... :confused: :rolleyes: But I would LOVE for it to downshift a little faster too. Sometimes I am going only 18 mph, floor it and it won't kick into first! Talk about frustrating!! It will then rev up to about 32 mph and shift, so I figure if I can floor it at 22mph or so and have it kick into first, that should still be fine. Thanks again for EVERYTHING.

http://www.a-p-group.com/cklasse/ThrottleLinkage.JPG

I think you are looking at the throttle cable. That would not be what you want to adjust. In this picture you CAN see a cable adjustment though. The black nut at the end of the cable housing; where it attaches to the metal bracket (midway up the washer reservoir).

If I am right about this being the throttle cable, look around, the trans cable is a similar arrangement. Remember, one cable pulls and one is PULLED.