At 45mph the rear pump should be pumping enough fluid to keep the car moving so I don't think it can just be a failed pump unless both failed at the same time. I'd suspect a failure in a mechanical connection of some kind, either the yoke to the output shaft or the splines to the front pump.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I suspect mechanical too
The bang was heard and felt

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81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project

Not sure you'd feel either the front splines or the yoke splines failing. I'm now concurring with the flex plate failure hypothesis. But in any case, the mystery is why anything like that suddenly failed. Did the rear end seize and cause the failure at a weaker point?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Transtec - Transmissions

Mercedes Benz 722.3 Transmission Manual « Brandon's Blog

Also see mitchell & atsg.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

I had a flex plate fail in my first Bronco and it was a loud bang with a jerk but it also made a awful noise with the engine running. I would think the same would be true regardless if the transmission is in gear or not on the Mercedes.

Does His year and Model have a Transmission with a Rear Pump?

The other question is with the Front Pump not functioning can the Car even get in gear to make it to 45 mph?
I know I don't have the answer to either question.

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84 300D, 82 Volvo 244Gl Diesel

I think 93 was the first year MB took out the rear pump... maybe it's 94 or later even. either way, yes, the 123 series all had rear pumps as far as I know.

I agree it's likely mechanical.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

looking at the link that Junkman posted,I would conclude
that since it is locking the drive shaft when in the PARK
position,that what ever broke is forward of the park pawl.

would this be correct assumption?

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81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project

^^ makes sense to me. I would check the front pump by removing one of the cooling lines and see if anything comes out.

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

No, it can't make it to 45mph without a front pump, but when at 45mph the rear pump should function enough for the car to continue moving.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I Got a good 83 tranz --to ship but greyhound is no longer a go deal-they lowered the limit to 100lbs, its in DFW-texas.

thanks, but at this point I am still trying to avoid r/r ing the tranny
if I can. If I do need to go that route, I have a few options closer to
home. But again thank you.

__________________
81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project