722.1 Transmission help??? - PeachParts Mercedes-Benz Forum

cooljjay · #1 04-23-2014, 11:33 PM

I have an issue, a rather bad one...I was letting my buddy drive my car to get more driving experience...I was telling him, don't be afraid to floor the car and the kick down switch under the accelerator...It seemed like he was playing speed racer in it...didn't think much of it...I then noticed the speedo needle jumping....odd...I went to run my mom out and the transmission is acting up....just driving normally it drives fine but out of the blue it will drop the gear and the speedo needle will go to 0....

I unplugged the kickdown switch, problem persists, fluid level is right at the max mark, took in on the freeway....no change...I finally just parked it, to dark to do anymore investigating..

Its an odd issue because, it feels like it does when you hit the kickdown switch to drop a gear but your foot isn't pressing the peddle down to hit the kickdown switch....maybe the solenoid is sticking?

Stretch · #2 04-24-2014, 03:18 AM

OK I'll use my ten thousandth post on you

When you say drop a gear do you mean goes into "neutral" or goes from 4 to 3 (say)?

If the gear goes down a gear then you have governor related trouble or as you say kick down related trouble - because the speedometer drive seems to be a related issue it seems to me that summit's slipping back there

Phillytwotank · #3 04-24-2014, 08:21 AM

Perhaps your kick down solenoid is stuck. Did you try to tap it?

cooljjay · #4 04-24-2014, 12:05 PM

Exactly, it drops from say 4 to 3 3 to 2 2 to 1 it does it in every gear.

I am also thinking the kick down is stuck or maybe my make shift bushing popped out.....I will be crawling under the car after coffee and checking both..

Zacharias · #5 04-24-2014, 01:09 PM

If the kickdown were stuck, I would have thought it would be revving very high through each upshift on acceleration as well.

If the solenoid wasn't disconnected, I would wonder if perhaps the switch had got something stuck in it that was making it engage randomly.

A long time ago I recall (on another list) a post by someone whose trans mount disintegrated and, in concert with a worn shift bushing(s), caused behaviour like this from the transmission actually moving under the car.

Stretch · #6 04-24-2014, 01:14 PM

Thing that worries me the most is the speedo dropping to zero - sounds worse than a stuck solenoid to me

cooljjay · #7 04-24-2014, 01:25 PM

I have a new mount under the trrans, I have replaced all the shifter bushings but one...

The speedo dropping is what has me worried also, its very odd.....the kick down is disconnected but it could be possible the valve is stuck just enough to not let pressure build up in the trans.....I am just very worried....there is no way I can afford a new trans and this one was just replaced in 2002..

Zacharias · #8 04-24-2014, 03:05 PM

Does the transmission behave the same way if you leave the lever in S?

If exterior inspection comes up with nothing, you could do worse than add a can of Seafoam, to see if that makes any difference.

If it's any consolation, the governor is accessible without removing the transmission, but the tail cone has to come off.

cooljjay · #9 04-24-2014, 03:08 PM

Well I checked all the bushings, they are all there, linkages all look good. I wired the kickdown plug, jumped underneath...and tapped the wire to the screw....and you can here it clicking....went for another drive and same issue....it appears now that it is revving up very high and not shifting until I take my foot off the peddle...then it will some times up shift...

I believe I tossed my old solenoid as it was dead so I can't switch one in....I am waiting for the manifold to cool down and then I will pop the bowden/pressure rod off and see if by chance it needs adjusting..

As I have 0 funds to toss parts on it....I will pull the seats up for the euro and switch the plates over and drive that....of course it has no fuel...so will need to siphon fuel out of the silver guy....lord I didn't need this...

cooljjay · #10 04-24-2014, 03:11 PM

Quote:

Originally Posted by Zacharias

Does the transmission behave the same way if you leave the lever in S?

If exterior inspection comes up with nothing, you could do worse than add a can of Seafoam, to see if that makes any difference.

If it's any consolation, the governor is accessible without removing the transmission, but the tail cone has to come off.

hmm good question, I put the shifter in S to attempt to kick it up or something but can't remember if it did anything different..

I have almost a full can of trans X in the trunk...I was thinking of draining some fluid and tossing that in....would it suffice?

That is nice to know...

Zacharias · #11 04-24-2014, 03:11 PM

You have a control linkage going to the transmission?

The only 722.1xx transmissions I am aware of are vacuum control only, no rod or cable.

What model is your transmission, exactly?

Edit: I was forgetting you have a '78 like my coupe, so I guess no vacuum control on the transmission and a control rod.

But I did not think those were 722.1xx. I have never looked at mine, to be honest.

Zacharias · #12 04-24-2014, 03:21 PM

I think your trans might be a 722.0.

I found this post in the archives, by Steve Brotherton of Continental Imports (transmission guru).

Not sure it will do anything for you, but it seems to clear up the misconception that your model of trans had no modulator adjustment:

The fixed modulators on early diesels are have a straight screwdriver adjustment under the 17mm cap nut (think its 17). As with movable modulators the key to the proper pressure is the eventual protruding length the device imparts on nthe valve inside the trans that it applies. A significant flair or soft shift can arise from putting a sealing washer under the device when screwing it into the trans. As the total length is the criteria adding the washer messes it all up. Move it in for harder shifts and out for softer. This trans is designed to have control presure control shift pressure and if no one has screwed the mod up then the proper mechanism for increasing shift strength is to make it shift later.

Also a follow-up from the OP Steve was answering:
Thank you all very much. I think it is all starting to make sense. There is a modulator adjustment access at the tail of the transmission housing on the passenger side just like C32AMG said. It has a 17mm cap.

801mbz · #13 04-24-2014, 03:29 PM

Check the nut on the trans to drive shaft flange.

Stretch · #14 04-24-2014, 04:33 PM

Quote:

Originally Posted by Zacharias

I think your trans might be a 722.0.

I found this post in the archives, by Steve Brotherton of Continental Imports (transmission guru).

Not sure it will do anything for you, but it seems to clear up the misconception that your model of trans had no modulator adjustment:

The fixed modulators on early diesels are have a straight screwdriver adjustment under the 17mm cap nut (think its 17). As with movable modulators the key to the proper pressure is the eventual protruding length the device imparts on nthe valve inside the trans that it applies. A significant flair or soft shift can arise from putting a sealing washer under the device when screwing it into the trans. As the total length is the criteria adding the washer messes it all up. Move it in for harder shifts and out for softer. This trans is designed to have control presure control shift pressure and if no one has screwed the mod up then the proper mechanism for increasing shift strength is to make it shift later.

Also a follow-up from the OP Steve was answering:
Thank you all very much. I think it is all starting to make sense. There is a modulator adjustment access at the tail of the transmission housing on the passenger side just like C32AMG said. It has a 17mm cap.

The 722.0s were three speed units fitted to V8 engines

However the 722.117 and 722.118 started life with rod throttle linkages (like most 722.1s) and an adjusting screw as described above instead of a vacuum dashpot. Later the rod linkage was dropped and they went "vacuum only"

cooljjay · #15 04-24-2014, 05:17 PM

Correct, I will double check but I believe mine is a 722.118 and it does have the rod....

I installed the bottle of trans-x.....at first appeared to be working better but still the speedo was droping to 0 and then back up then jumping around...

I drove it around some more and its like it is now wanting to stick in a lower gear and not shift back up..

So now I am going to but some of the euro back to make it drivable so I have a car, until I with the help of you guys an help me out..