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  #1  
Old 03-25-2008, 12:14 PM
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Location: Charlotte, NC
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Help - Missing Vacuum Modulator Spring?

This past weekend a friend and I rebuilt my tranny on my 92 300E. All was going pretty well until the last few steps of re-assembly and we came to re-installing the vacuum modulator (black). We noticed the picture in the tranny rebuild manual showed a spring between the modulator and the plunger that the modulator operates. But.....we could not find the spring anywhere and so we're not even sure the spring ever existed or is even required.

I called Phil at FastLane (where I bought the rebuild kit) and his pictures of the modulator he sells do not show the "plunger" or the spring, so he was not able to help me.

I've searched all over this site for the pictures, or discussion, that would tell me if I need to be looking (or in this casing, trying to buy) for the mystery spring.

The reason this search all came about is due to the fact that upon the initial test drive, all gears are present, BUTTTTTT, the transmission is waiting until the RPM reaches max level until shifting from one gear to the next. I have read many, many threads regarding this issue as well and it seems the consensus diagnosis is always the Bowden Cable, or the Kick Down solenoid. I have checked the tension of the Bowden Cable and it is fine. I have not been any farther than that in trouble shooting because I want to know if I need to look for the Spring that may or may not exist.

My thought (and it could be totally out in left field), is that the problem is really a severe case of "flaring" without the spring present. This may sound ridiculous to most of you, but let me tell you that after rebuilding one of these things you are mentally exhausted. So I'm just trying to make sure I have "All the parts back in the tranny" before I start troubleshooting.

I have attached a picture of what the rebuild manual is showing.

Thanks for ANY help you guys can offer.

Attached Thumbnails
Help - Missing Vacuum Modulator Spring?-vacuum-modulator-picture.jpg  
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92 300E - 116K miles - Sold
77 Euro 350SL - 67k miles
94 Explorer 147k miles
2009 Hyundai Genesis - 65k miles
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  #2  
Old 03-25-2008, 01:08 PM
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Quote:
Originally Posted by DAVID LEE View Post

I've searched all over this site for the pictures, or discussion, that would tell me if I need to be looking (or in this casing, trying to buy) for the mystery spring.



I have attached a picture of what the rebuild manual is showing.

Thanks for ANY help you guys can offer.
I am in the process of rebuilding the transmission from my 1995, E320 and just went out and can tell you that my vac. modulator valve does not have the spring either. I think that the spring may have been used prior to the updated design in 1981. I checked EPC and it does not show the spring for my transmission. You may want to check EPC using your VIN to make sure.
The online EPC is free at https://epc.startekinfo.com/epc/home.jsp

You have to give a credit card number when you register but there will not be a charge for a one year subscription.
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  #3  
Old 03-25-2008, 01:28 PM
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Fred1948 - thanks. Now I can start looking in the "logical" places for my problem. The plunger must be moved by fluid pressure, and the modulator is "pushing" in the opposite direction.
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  #4  
Old 03-25-2008, 04:41 PM
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Is there a rebuild "kit" for the 722.4?
Anyone know where I can get it? I can't find it on FastLane...

Cheers
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  #5  
Old 03-26-2008, 10:22 AM
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Join Date: Jun 2002
Location: Charlotte, NC
Posts: 102
Just an update - Last night I decided to take the car a few blocks to get something to eat and lo and behold the car is shifting at the appropriate shift points - Yea!!!. I do need to adjust the modulator due to flaring between 3 & 4 (I hope it's not some other issue, but won't rule out due to some documentation I've read.), but "somehow" something got fixed while it was sitting in my garage.

This has been quite an experience - one that I'm not sure I want to repeat, but as time lapses and memories of the struggles wane, I may attempt again.

Good luck to anyone attempting a rebuild.

Some things I didn't do, but should have due to simply not carefully reading the rebuild manual.

1. Drill out the rivits in the K1 and K2 clutch and change the o-rings (might be my flaring problem). This just seemed like something that could go really wrong and I decided not to take the risk of screwing up the whole assembly.
2. Insure the metal clutch plates went back in the correct order. Yes - there is more than one thickness of metal plates and the manual (The Benz version) says to put them back in a particular order.
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92 300E - 116K miles - Sold
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94 Explorer 147k miles
2009 Hyundai Genesis - 65k miles
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  #6  
Old 03-26-2008, 11:09 AM
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Quote:
Originally Posted by DAVID LEE View Post
Just an update - Last night I decided to take the car a few blocks to get something to eat and lo and behold the car is shifting at the appropriate shift points - Yea!!!. I do need to adjust the modulator due to flaring between 3 & 4 (I hope it's not some other issue, but won't rule out due to some documentation I've read.), but "somehow" something got fixed while it was sitting in my garage.

This has been quite an experience - one that I'm not sure I want to repeat, but as time lapses and memories of the struggles wane, I may attempt again.

Good luck to anyone attempting a rebuild.

Some things I didn't do, but should have due to simply not carefully reading the rebuild manual.

1. Drill out the rivits in the K1 and K2 clutch and change the o-rings (might be my flaring problem). This just seemed like something that could go really wrong and I decided not to take the risk of screwing up the whole assembly.
2. Insure the metal clutch plates went back in the correct order. Yes - there is more than one thickness of metal plates and the manual (The Benz version) says to put them back in a particular order.
Did you do anything with the valve body?
I took mine completely apart and cleaned everything (required the better part of the day as I was very careful to keep all the parts in order and clean them individually just before reassembly). There was a lot of sludge in the valve body and some of the valves were difficult to remove because they were sticking. On reassembly everything moved freely. I also installed the K1 spring upgrade kit in the valve body. The part number for the kit is 126 270 44 77 and the price from the local dealer was $7.00. At first they told me that this was not a good part number because it wasn't listed on the EPC. They then checked on another computer and found the part number, so be persistent if you get told that it is not a good number! This kit is designed to prevent 2-3 shift flare.
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  #7  
Old 03-26-2008, 11:28 AM
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Location: Charlotte, NC
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I did not disassemble the valve body. The transmission was extremely clean and free of sludge of shavings. I may have to do that later. I have never been into a transmission in my life, and the fellow that was helping me (he has done many trannies on Ford / GM products years ago) said that he usually didn't take the valve body apart unless there was some reason to think an issue existed within the valve body. Therefore, I did not open it up. However, reading some of the threads has given a level of confidence that I did not previously have, so it might be something that I do in the near future.

I will keep your comment about the K1 spring upgrade kit in mind. That may clear up ALL my little issues.

thanks Fred (I assume that is your name), and BTW, were you born in 1948 - so was I.
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92 300E - 116K miles - Sold
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94 Explorer 147k miles
2009 Hyundai Genesis - 65k miles
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  #8  
Old 03-26-2008, 12:50 PM
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Quote:
Originally Posted by DAVID LEE View Post
I did not disassemble the valve body. The transmission was extremely clean and free of sludge of shavings. I may have to do that later. I have never been into a transmission in my life, and the fellow that was helping me (he has done many trannies on Ford / GM products years ago) said that he usually didn't take the valve body apart unless there was some reason to think an issue existed within the valve body. Therefore, I did not open it up. However, reading some of the threads has given a level of confidence that I did not previously have, so it might be something that I do in the near future.

I will keep your comment about the K1 spring upgrade kit in mind. That may clear up ALL my little issues.

thanks Fred (I assume that is your name), and BTW, were you born in 1948 - so was I.
Your assumption is correct and yes I was born in 1948.
This is the first automatic transmission that I have ever rebuilt and I was impressed at the amount of information available at little or no cost. I am taking my time and have ordered several small parts, shims, retaining rings, etc as I have discovered that I need them. I find the dealer prices on small parts to be very reasonable and usually take 2 days to get. I did replace the "hidden" o-rings. On my transmission the K1 clutch had a retaining ring that could be removed to replace the o-ring and the ring came with the genuine gasket/seal kit. The K2 required drilling the rivets and replacing with 5x.8mm flat head screws after tapping the holes in the drum. I had a very difficult time locating the o-ring for K2 (Mercedes does not sell it as a separate part). I finally got the o-ring from a very helpful owner at Jaggi Transmission who was in the process of moving his business from Texas to Michigan. He included a copy of instructions from a Transtar Industries product bulletin. Probably if you can find a transmission shop that buys parts from Transtar they would be able to get the kit. The kit/pn's on the bulletin are K55900D-4 and K55900E-4; I don't know which one is for K1 and which is for K2.
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  #9  
Old 03-26-2008, 01:40 PM
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Fred:

I should have taken much more time to do mine. I had access to a tranny resource for 2 days, so out of "fear" I paced us to get done in 2 days. My kit had the o-rings with the screws. All the o-rings and teflon packages were labeled with MB part numbers, so perhaps our kits came from two different sources.

Anyway - good luck with your rebuild and perhaps we'll chat again in the future?

Dave
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92 300E - 116K miles - Sold
77 Euro 350SL - 67k miles
94 Explorer 147k miles
2009 Hyundai Genesis - 65k miles
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  #10  
Old 03-26-2008, 06:28 PM
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Quote:
Originally Posted by DAVID LEE View Post
Fred:

I should have taken much more time to do mine. I had access to a tranny resource for 2 days, so out of "fear" I paced us to get done in 2 days. My kit had the o-rings with the screws. All the o-rings and teflon packages were labeled with MB part numbers, so perhaps our kits came from two different sources.

Anyway - good luck with your rebuild and perhaps we'll chat again in the future?

Dave
Could you please post the part numbers for the o-rings and screws. It would be good information to have for future reference.
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  #11  
Old 03-26-2008, 08:22 PM
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I will do that - providing of course I haven't thrown them in the trash. I think I kept all the left over o-rings and teflon rings and I think I kept those parts as well - I thought I might need to go back into the tranny.

I just got back from a test drive after adjusting the modulator and the tranny is shifting pretty nicely. I think I'm going to stiffen up the shift just a tad more and then I think I'm going to take a "car breather". There's just so much of this a guy can take and hold down a full time demanding job.

I just checked the bags of parts that I kept and it looks like I threw the bags with the part numbers for the conversion kits away - sorry. I did get the overhaul kit from Fastlane and it is manufactured by Precision Int. I think the only parts that Precision manufactures are the clutch disks though because all the o-rings came in bags marked with mercedes part numbers.

I would suggest calling Phil at Fastlane and asking for their number. I would give it to you, but it is not on any of their documentation. If you get ahold of Precision, the document number appears to be IS-5613, and it has a rev of 7/00.
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92 300E - 116K miles - Sold
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94 Explorer 147k miles
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  #12  
Old 03-29-2008, 10:22 AM
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I was cleaning up the garage this AM and found a parts bag with the three screws and the o-ring. So...here are all the "verbage" on the bag.

SUB-K5601, Mercedes 722.3 & 7 2.5, IS-5601, 07136.

I realize these aren't MB numbers, but must be Precision Intl. numbers. I think these should help once a phone number could be obtained for the company. I'm pretty sure there was another bag for the other clutch.

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