722.6 Transmission Refresh. DIY and questions.

[MEPEH]

Ok. So here's my next project.
I have a 1998 CL500 with about 200k miles on the original transmission.
The previous owner "forgot to mention" that the tranny was quitting and i inherited a surprise on my way back.

First symptoms:
A few hard shifts 2-3 gear and it went into limp mode.
Stuck in 3rd gear. CEL on with generic p0700
(TCU malfunction)
Also Trouble codes for speed sensor.

Opened the coffin box and discovered oil.
Replaced the harness connector + TCU
Dried the connectors and everything was great for the next 200 miles.

Second symptoms:
2 more hard shifts 2-3 and transmission gets stuck in 3rd.
No check engine light until it goes in second gear limp mode.
CEL on with p0715. Speed sensor again.

This is what i just ordered and plan to replace.
1 Conductor Plate

2 Pressure regulator spring 2-3 gear

3 Sonnax Mercedes 722.6 Overlap valve sleeve kit.

4 Fluid Fuchs titan atf 3353 (They make the fluid for Mercedes. Too much controversy with other oils so i'll stick to what's been tested)

5 Pan Gasket and fluid Filter

6 Dipstick

7 Washer for the drain nut

8 Lock Pin for the filler tube

9. Also PLEASE don't forget about the harness connector. (I replaced mine a few days ago and got rid of all the oil that leaked into the TCU)



Also plan to order carsoft Today to reset the codes. ( Or maybe C3 or C4 ?)

I doubt i'll get all my parts before the week ends so plan to do it next weekend.

What did i miss ?

P.S: I'm ordering 2-3 pieces of each. So if anyone wants a "kit" to refresh the 722.6 - PM me for details.

[RichardM98]

Compression washer (seals) for the drain plugs on the transmission and convertor. Very cheap at dealer. Also, a 'dipstick tool' to set fluid level correctly - very important. Foolish to do service without it. Also, replacement plastic lock tab on cap for dipstick tube. Cap may stay on without it if o-ring inside is good. Some people have reported it came off while driving.

[MEPEH]

Originally Posted by RichardM98

Compression washer (seals) for the drain plugs on the transmission and convertor. Very cheap at dealer. Also, a 'dipstick tool' to set fluid level correctly - very important. Foolish to do service without it. Also, replacement plastic lock tab on cap for dipstick tube. Cap may stay on without it if o-ring inside is good. Some people have reported it came off while driving.

Thanks. Ordered those too.
Will edit my post to include in the list

[97 SL320]

Tension spring for 2-3 gear.

I'm guessing this a valve body part since you are not pulling the trans. Is this a Mercedes or aftermarket part? Numbers?

[MEPEH]

Originally Posted by 97 SL320

Tension spring for 2-3 gear.

I'm guessing this a valve body part since you are not pulling the trans. Is this a Mercedes or aftermarket part? Numbers?

Everyone recommends replacing it. It's a 2$ item and saves a lot.
It will smooth the shifting from 2-3rd gear (since these are the most used)
It's a DIY and this is where you can find details
722.6 Pressure regulator spring replacement - Benzworld.org - Mercedes-Benz Discussion Forum

Shouldn't take more then an hour if that's the only procedure you do.
No need to pull the tranny. Just the pan

By the way. I purchased a couple of them. If anyone is interested PM me.
Should get them early next week. Will try to take as many photos when i work on mine

[97 SL320]

Another question, was your speedo still working even with the 0715 speed sensor code? I've got a 97 E320 parts car that stays in 2nd limp / CEL on. One time after start up it did shift fine but from the next key cycle it went into limp.

Another oddity is when the trans is stuck in 2nd,the dash mounted high beam indicator is on and there is a warning message on the driver info display. ( it is ABS or ASR , don't remember. ) The speedo works through all of this so it either gets a speed signal from the ABS sensors or the trans output shaft speed sensor is intermittent.

Somewhere I came across some info that these cars used a front ABS sensor to drive the speedo.

[MEPEH]

Originally Posted by 97 SL320

Another question, was your speedo still working even with the 0715 speed sensor code? I've got a 97 E320 parts car that stays in 2nd limp / CEL on. One time after start up it did shift fine but from the next key cycle it went into limp.

Another oddity is when the trans is stuck in 2nd,the dash mounted high beam indicator is on and there is a warning message on the driver info display. ( it is ABS or ASR , don't remember. ) The speedo works through all of this so it either gets a speed signal from the ABS sensors or the trans output shaft speed sensor is intermittent.

Somewhere I came across some info that these cars used a front ABS sensor to drive the speedo.

Correct. Fron ABS Sensor dictates vehicle speed for the dash and ECU

The speed sensor P0715 is for transmission control purposes.

PLEASE REMEMBER: Once the Limp Mode 2nd Gear is engaged, the Trouble Code will stay in the Transmission Module until erased with a MB STar Tool.

Generic OBD Scanners WILL NOT ERASE TRANSMISSION CODES
Disconnecting Battery, Sleeping in the car or dancing around it will not help either

(Sorry for the caps, i've been researching this topic a lot and people rarely mention it. Lots of people get convinced to get a new TCU for 800$ rather then erase the trouble code in the original one)

[Gilly]

Magnetic pad for in oil pan, i don't think your 1998 will have it, I have one around here I can grab the PN off of if you need it.

The new conductor plate should come with the covers for the solenoids, be sure to install these, they are NOT just for shipping purposes, they were added in later in production and should be there, again your 1998 might not have the covers originally. If you don't have the covers with the new conductor plate I would get them before putting the valve body back in.

[MEPEH]

Originally Posted by Gilly

Magnetic pad for in oil pan, i don't think your 1998 will have it, I have one around here I can grab the PN off of if you need it.

The new conductor plate should come with the covers for the solenoids, be sure to install these, they are NOT just for shipping purposes, they were added in later in production and should be there, again your 1998 might not have the covers originally. If you don't have the covers with the new conductor plate I would get them before putting the valve body back in.

Yes, please. Can i have the part number for the magnets ?
Everyone mentions it but i haven't found any p/n

Appreciate your help

[MAVA]

Mepeh,

Good job on your analysis, I would do a fluid exchange on the whole transmission. You'll use four to five gallons of fluid, so you get 100% of the fluid out not 80 to 90% with a torque converter change. I did one on the same year vehicle a month a go. I would change out all the solenoid o-rings, each solenoid has two o-ring's as these o-rings will be disturbed when the conductor plate is replaced, but you may have to go aftermarket with those. Clean out the filters on the two regulating solenoids, and swap out upper shift solenoids with the lower ones.

Here is cheaper source for the fluid.

item detail

Best of luck,

Martin

[MAVA]

ohhh, Inspect the Pressure regulating spring on the valve body. I'd even replace it, Sonnax and Mercedes sell it.

Martin

[MEPEH]

Originally Posted by MAVA

ohhh, Inspect the Pressure regulating spring on the valve body. I'd even replace it, Sonnax and Mercedes sell it.

Martin

Thanks. This part is on the list.

[MEPEH]

Originally Posted by MAVA

Mepeh,

Good job on your analysis, I would do a fluid exchange on the whole transmission. You'll use four to five gallons of fluid, so you get 100% of the fluid out not 80 to 90% with a torque converter change. I did one on the same year vehicle a month a go. I would change out all the solenoid o-rings, each solenoid has two o-ring's as these o-rings will be disturbed when the conductor plate is replaced, but you may have to go aftermarket with those. Clean out the filters on the two regulating solenoids, and swap out upper shift solenoids with the lower ones.

Here is cheaper source for the fluid.

item detail

Best of luck,

Martin

I ordered 20 liters of FUCHS fluid. I'll just use as much as it takes and sell the rest.
I've read a lot of different opinion about the ATF and, I'm already saving money by not buying it from the dealer, so i'll just go with FUCHS.
May be next time i'll try Shell.

I've read about swapping the lower solenoids with the upper ones.
Do you know what the resistance should be ? I know you can measure and see if it's within acceptable range.
Also, where do i get the seals for the solenoids from ?

[MEPEH]

Now my biggest dilemma is:

How do i reset the Trouble Codes when I'm done ?

Carsoft 7.4 is only 85$ but i'm afraid i'll curse everyone trying to make it work and will have limited access to the rest of the modules on the car.

Star C4 is overkill in my situation @ 800$ for the Kit

Star C3 seems reasonable at about 350$, but i haven't found a seller i can trust yet.

(I used to be a bosch certified technician and have experience with good scan tools and german cars. I just switched to Mercedes after owning pretty much all the BMW models up to 2006. I have the latest BMW ICOM that costed me about 4k and used to do everything related to warning lights and electronic malfunctions)

Now i'm trying to find something for Mercedes that would give me similar performance without forgetting i'm just a DIYer

[Hirnbeiss]

It sounds like you've covered the internals, but while you're there ...
with 200k miles, the flex disc and shifter linkage bushings may be due for replacement.