With my measuring tool and plenty of Redline D4 in hand, I hit the open road to see how low the ATF level was on the 98 E300D I just bought. After a good half hour run, I checked the level and it was in the middle of the range....the 25C range, that it is! Yikes!! But, the shift quality was perfect. So I've begun adding very gradually....about 16 oz. so far....but's still a bit low. Needless to say, I have absolutely how long it's been leaking. But it will be fixed next week.

How low would ATF have to be to damage the 722.6 tranny?

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I would say a lot of fluid loss more like low 3 or 4 qts would cause damage - the 722.6 is a bit overfilled (as said by some trans builders)

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Great....I doubt if I was more than a quart low.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

As long as it is operating, I wouldn't see that there was anything to be concerned with - not yet anyway, provided it hasn't been run during such a loss that it overheated in the past.

So, what, would it go into Limp Home Mode if fluid were sufficiently low?

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I would imagine it would as soon as it detected a fault....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

That's pretty cool if that's the case...nice fail safe. I wonder if there's a way to confirm that that's part of what Limp Home does.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

firstly you are running a pre 2000 722.6 transmission. It has an aichelles heel in it, its the 2nd clutch bearing surface (a bushing - later replaced by a bearing in post 2000 transmissions)

If the pump goes dry, or works on overheated fluid that bushing goes out of round and your input shaft then wobbles, which does 2 things.

1 grind the planetary gear sets at the front
2 bang the impeller in the torque converter.

The golden rule to keep this transmission working is fresh compatible fluid with 30,000 mile intervals and correct level of fluid.

the other heavy ulfbehrt sword strike is the limp home mode in the 722.6 trans - no generic reader or battery disconnect clears it, you need the MB star software or something similar to reset it. Its pricey.

A general rule of thumb with this trans is to replace the electric connector bushing every 30,000 miles or so with a genuine updated mercedes part (which is cheaper to buy at the chrysler dealer )

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Makes sense. This tranny was resealed at 35k and that bushing is leaking at 73k.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I suppose it's a good thing that the fill port was sealed. That greatly reduces the possibility the PO topped it off because it had a dangerously low fluid level. How low the fluid level got before the 35K mile resealing is another question.

Sixto
87 300D

In 14+ years / 131K miles - my car never evidenced; Limp Mode. I don't know what that would be to experience outside reading about it.


My response was more of a symptoms-based transmission problem while either driving or at start-up and shifting into gear. I never had a problem with the driving aspects of my transmission. Never saw the limp mode either in 14 years, 131K miles.

Do you have a set of records on that car to reference?

The known unknowns surfacing about your car would cause me to want to visit with the previous owner(s) if I could. I performed a complete routine servicing of it's transmission myself just short of 100K miles, which was about 5-years after I bought it / put it into service. It never failed to perform for me.

Interestingly, the port was sealed but the horizontal tab on the locking pin was broken off.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

My experience reflects that if you have a severe, immediate leak of transmission fluid (think blown hose) the car will stop before it ruins the transmission.

__________________
Jim

I have never run a Merc out of fluid, but when I had a leaky hose on my Ford this is what happened.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Not a tranny expert by any means, but...

I have to think that if you lost a cooler hose, or the pan breached by road debris, that the sudden loss of fluid would cause the internal hydraulic pressure to drop.

This would cause the clutch(es) to drop out and effectively put you in neutral, no?

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech