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1998 S420
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294 Posts
Discussion Starter #1
Howdy folks,

About eight years ago I sold a perfect mint condition S420 to a good friend of mine. Shoot forward 4 years ago and it gets a "problem". My friend did not mention much to me about it other than he was going to fix it.

Unfortunately, he now has MS, is on disability and is unable to afford to fix the car. As a result I have bought the car back off him and I want to get it running again.

After putting in another battery (I put a new one in for him last October and it's already dead, must be a draw somewhere), it seems that all electrics are good. Turning the car on, despite sitting for four years in a garage, the engine starts right up. NO CEL, no codes on the OBDII scanner, except I think the transmission is gone. 2nd and reverse seem to work but the trans sounds like a locomotive on train tracks, loud and grindy.

Does anyone know the approximate cost to rebuild once of these fellas?

It's the 4.2l V8.

Cheers!
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,009 Posts
What year is the car? Two different tranny's were used, depending on year, and potential issues are very different.

That noise could also be one of the flex discs gone bad.

Jon
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,009 Posts
I'd crawl under the car, check the flex discs, pull the transmission pan, change fluid and filter, and check for debris in the pan. I'd probably change the conductor plate and connector block if I didn't find debris, or get it rebuilt if I did.

Costs will vary all over, depending on what is found. Until the exams I've mentioned are done, you won't know.

Jon
 

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Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
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22,366 Posts
If you do buy a replacement transmission, I would like to buy a core. Actually, I just want the bell housing for an m119 from a 722.6. It’s just to do some testing for some customization. So maybe I could buy your core?? :)
 

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1998 S420
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294 Posts
Discussion Starter #6
Thanks for the all the tips guys. I am a novice mechanic so have a lot to learn. Is it hard to remove the tranmission pan and to change the fluid/filter?

@Fonzi, hopefully I can rebuild/fix this one. What is a core by the way?

Cheers

Mike
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,009 Posts
Trans pan and filter are easy. Look up YouTube video for 722.6 DIY fluid change.

A core is a broken unit used as partial exchange on a rebuilt one.

Jon
 

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01 ML55, 96 S320
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302 Posts
I would definitely drain the fluid and take a look at what you find. Get a good set of jacks and place them on the subframe so you have some room (the pads under the doors are great but when you're crawling out from under the car they get in the way). That should tell you right away what's going on unless you can get it scanned and read the TCM. Either way I would still want to see the fluid for myself. Obviously that's just a start, the pan could be hiding things as well but draining fluid is less messy and a good starting point.
 

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1998 S420
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294 Posts
Discussion Starter #9
Thanks for the tips guys, will be moving the car into the garage soon so I can do that.
 

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1998 S420
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294 Posts
Discussion Starter #10
bought a transmission dipstick, and the requisiste o-ring and new locking cap off amazon, and finally got a chance to check the transmission oil and engine oil. Whilst cold, on a level area, both of them were way above what the max level should be. The transmission oil level was even way above what it should be when warm!

Could this be water vapor from sitting so long?
 

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1994 S600 Coupe, 1995 S600 Coupe
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2,009 Posts
Doubtful that it's water vapor.
If you can, check the fluid level after the car is warm and at operating temperature. If the car sat for awhile, fluid could have drained back into the transmission from the radiator cooler. If it is still too high, drain it, pull the pan and check for junk in the pan and change the filter. If things are clean, refill to the proper level and test drive. You'll need a new pan gasket set and a filter. They aren't very expensive.

Jon
 

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01 ML55, 96 S320
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302 Posts
Did you check it with the engine running? If not, run the engine cold and see what it shows. You should see either nothing or a little bit. If running and cold and the fluid is all the way up the gauge then it's way overfilled.
 

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1998 S420
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294 Posts
Discussion Starter #13
Did you check it with the engine running? If not, run the engine cold and see what it shows. You should see either nothing or a little bit. If running and cold and the fluid is all the way up the gauge then it's way overfilled.
whilst the engine seems to be running fine, the transmission is making some serious grinding noises from the second I turn the car on. Even when it is in park. I don’t really want to turn it on again until I can take a look at the trans.
 

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1994 S600 Coupe, 1995 S600 Coupe
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Yikes. If that's the case, I wonder if it might not be a torque converter or flex plate issue. You might try turning the engine over by hand, using the bolt on the crankshaft (normal engine rotation direction only), and have somebody listen under the car and try to identify where the noise is coming from.

Jon
 

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01 ML55, 96 S320
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302 Posts
Yikes. If that's the case, I wonder if it might not be a torque converter or flex plate issue. You might try turning the engine over by hand, using the bolt on the crankshaft (normal engine rotation direction only), and have somebody listen under the car and try to identify where the noise is coming from.

Jon
True, didn't think about the flexplate. I was trying to think what moves (spins) in Park. TC, FP, oil pump....input shaft? Agree with test, see if you can listen to where that noise is coming from.
 
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