Hello everyone,

I am new here (first post) and I am hoping someone could give me some advice or possibly make some sense out of the problem I am having with my transmission.


I currently rebuilt my car's transmission (w140 , 95 S500) which was having problems with no reverse and high RPMS on the freeway.
I have had the car since 2010 with both these problems, although the reverse was intermediate it actually went out completely 3-4 months after I got the car.


Car had been siting since and after 4 years of sitting in the garage; I took on the project this January and completed the overhaul a couple of months ago.

I worked little by little on it in my basement after long working hours. As expected B3 reverse plates were worn completely, and some plates were worn but not too badly. Opened and cleaned the Valve body completely to the T and made sure all the things were in spec. I installed all the seals, clutch packs and gaskets that came in the kit.
The only things I re-used from the transmission were the steel plates, the two bands and the converter (dumb me for not changing the TC)

Now my car is back on the road. It needs little adjustment because it is shifting a bit on higher RPMS but it is barely noticeable. No slipping, no flaring...it is simply perfect and my reverse has never been any better.
It kicks in gear nice and firm and has plenty of torque. Never slips and I don't have to wait 5 seconds for it to engage like some people that are having that problem.

The issue that I am having is the High RPMS on the freeway which EXISTED ever since I got the car.
I am rolling at 3700 RPMS at 80mph.

This is a 722.370 4 speed Auto with a Non-Lockup Torque converter.

The car starts in 2nd and kicks 3 and 4th accordingly.
I know 100% i am in 4th because i can count the gears as I am speeding and I can downshift to 3rd from D and the RPMS move up higher.

I checked my rear differential and I have the correct 2.65 diff MB put on the 1995 V8 5.0 S500's. It even says so on the Dif housing 2.65.

The Torque converter is the only thing I haven't changed and now I am thinking this could cause the issue but not sure. If it was the TC, wouldn't the car have issues on each gear and even at start.

What could it be? A full rebuild did not fix the high RPM issue.
I am running out of options. I am getting a used TC from someone who has a few of these cars for parts but to I am not too optimistic that it will fix the high RPMS on higher speeds.

To give you a better idea what my car does, here it is.
https://www.youtube.com/watch?v=VLyRK7GOnZs

This is where it should be (from someone else's S500 of the same year)
https://www.youtube.com/watch?v=Cjm1ZFimLK8


So any ideas?
High RPMS on freeway. I also noticed during kickdown from stop, the car will pass redline in 6K RPMs and changes to 2nd gear at 7 RPMS.

I am uploading some pictures of my rebuild.

Attached Thumbnails

         

Thought I could get someone's opinion on here regarding this issue but looks like I am alone with this ..

I checked out the videos and you have music on in the one you took so I couldn't compare the sound of the engine.

Tires the right size I take it.

Have you checked the odometer against mile markers? ( or set the cruise at 60 mph and see how far you have traveled after exactly one minute.

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It does sound like something is slipping.

If you were to put the measured rpm (and tyre size etc) into an online calculator would you then get the correct road speed for every gear?

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Don't leave that there - I'll take it to bits!

Did you measure the torque converter to see if it is in spec?
In the MB rebuild book, there is a dimension you need to measure to see if the TC is damaged and expanded. A expanded TC will cause higher RPM's then a good one because the internal distance between turbine vanes and stator are too big.
This will however be noticeable in all gears, but none the less, overall RPM's will be higher. Funny thing is, the car might actually feel sportier with a bad TC because you now theoretically coupled the engine into a higher power range. Just like a racing torque converter.

Can you force the car into 1st gear? I don't know about the w140's, but the w126's have a indent in the 2nd gear shifter position to activate 1st. 1st gear is electrically activated, unless you really stomp on it from a dead stop either with or without hitting the kick down button.

Lets just make sure you are starting off in 2nd and not first..
Because from that video, it looks like its in 3rd, and around 0:53, it downshifts to 2nd.
If that's the case, totally disconnect your boden cable, and manually shift to ensure you have all gears. Car will almost instantly shift into 4th upon takeoff. Scratch that ideal, the w140's are vac activated boden...

Also another thing you can do first is, disconnect the single power cable going to the first gear/kickdown solenoid on the back of the trans. I think your w140 has the downshift button behind the gas pedal. This might be faulty, and causing the trans to always be 1 gear behind. Its could be either that, or a bad internal valve inside the solenoid. This can easily be removed from the trans and bench tested with 12v to see if the valve properly opens and closes. Now that im thinking about this, I suspect that's whats going on.

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Are you 100% sure a 1995 V8 car starts in second gear still? 400E started in first as did the late I6 cars from my understanding.

Doing quick RPM versus gear math, sounds like the car is in 3rd gear to me. Stock 235/60R16s, 1.44:1 for third gear, 80mph equals 3799rpm...before converter slip. Of course the speedo could be off slightly as could be the tach. Which is right around your displayed RPM.

Where is the wide open 1-2 shift? 45-50mph?

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First, allow me to apologize in advance for not getting back to you sooner.
I didn't come back on here sooner as I figured I wouldn't get any replies.


Speedometer works correctly, I struggle to keep up with cars on the freeway as I am over-reving (75mph @ 3.7 rpms) so I cruise at 60-65mph and every passes me. I have confirmed my speed on my phone's GPS as well. The sound of the engine sounds like it's running fast but you won't hear it because there is not much load and the W140 is mostly quiet.

Tires are the stock 18' AMG monoblock II rims but there was no difference even when I had the 16' rims which I used to put on for the winter.

It is not slipping, it changing gears pretty nicely, sometimes 2nd to 3rd a bit hard but no slipping. The only time I feel like it could be slipping is in the final gear it where the RPMS increase and the speed increases but not as quick as the RPMS. If it's slipping in final gear, it is not noticable.


Car stars in 2nd and if I press the kickdown, it goes to first and has a lot of power and torque. First gear red lines at 25mph (is quiet short actually)
Normal operation, car starts in 2nd from a stop. As the speed increases, I can feel the gears changing 2-3, then 3- 4th. Once in fourth which kicks in at 35-40mph at cruising speeds @ 1.7 rpms.
It is a direct engagement, there is no slipping during all the gears change.
I know I am in 4th for sure.
I am not disagreeing with what has been said, it is actually matching the speed and RPMS as if I were in 3rd, but the car is actually in the final gear.

I highlighted your comment with green and I think I am with you completely. It looks like the Torque converter is slipping in the final gear.
You are correct that it might actually be slipping in all gears as I have noticed, everytime the car changes gears, it is around the 3000-3200 RPMS range. I believe the gears should change between 2000 -2200 RPMS at normal driving speeds.

So it is highly possible, the torque converter inside could be slipping as the pressure increase.
My assumption is that eventhough this model doesn't come with a Lock-up Type TC (which lowers the Rpms once cruising at high speed on the freeway), my TC might not be able to create the required torque at lower RPMS unless more 'gas' is applied which increases the oil pressure in the TC.
Also, as you mentioned, my car feels like it has a lot of unnecessary torque like in a sport car at cruising speeds. e.g if I am on the freeway doing 70 mph @3300 RPMS; If I want to speed up, it pulls very hard and fast. If there is a hill, it will not downshift as the car is already in the torque band. This is also another reason why i feel like the TC is slipping and engaging and making the Torque at much higher RPMs. From a complete stop, if I hit kickdown which engages 1st gear, it shifts to 2nd gear passing the redline @ 7000 RPMS ; Redline is at 6000 RPMS.


My understanding is: a slipping TC would case high rpms at all gears, gears shifting at higher RPMS then normal (which also explains why the car passes redline at full throttle) and also a high torque band at cruising speeds.

Which manually did you look to check the TC. I did not have a TC section in my 722.3/722.4 manual.

At full throttle from 1st to 2nd shift happens around 25-30mph. It seems a bit short for a 1st gear and I also noticed the shifting happens pass redline. Changes @ 7000 RPMS instead of 6000 RPMS.


I am not sure of the 400E body, but the pre-facelift 91-93 W140s came as the 400SE/400SEL which might be the same as the 400E. They came with a smaller V8 (4.0l I believe and in 93+ they went to a 4.2l). Although the same, the W140s had different valve bodies which made the car start in 2nd. The 96-99 which came with the 5 speed, had an S and W button which controlled 1st and 2nd gear start. Mine does not have that.

Thank you very much for all your replies guys. I understand reading all this must be quiet frustrating. I just received a used TC from a guy in NY which has a junkyard of these cars. I am hoping it will fix this issue

By the way, i agree with you. It looks like I am in 3rd. Give or take a couple hundred RPMS but it very close as if it was 3rd.
In this video i made a while back, you can tell the shifter in 3rd and 4th and the difference in speed - https://www.youtube.com/watch?v=tyfSLk-kmpc

can you do a torque converter stall test. if its stalling at higher rpm than specified then you need a new/rebuilt converter.

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Here is the page from the trans book about measuring the TC.. it should be the same for your model.

Attached Files

tc spec.pdf (164.6 KB, 176 views)

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Just my MB's:
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With the brakes pressed and pedal to 3/4 it starts to pick up at 2300 rpms to 2400 rpms. No go on lower rpms though.

Thank you for this, I will take a look at the other converter I have and see what measurements that comes out to.

The only other thing I could think of would be the vacuum modulator.
Dunno if this helps any, but passing along: http://www.w124performance.com/docs/mb/transmission/trans_722_Mitchell2.pdf

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