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#1
06-25-2013, 03:17 PM
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Diff ratio
How much different is the gear ratio in a 1985 300Sd compare to a 1984 300D? I was told the diff on the 85 SD is better than the one in the 300D, I was given a 1985 300SD using as part for the odds and end which I am taking apart to reboot the shaft (if they are in good shape) to use on the 300D. If the diff is better than one in the 84 300D I might aswell go the distance and take the entire rear end out.
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1984 300D, 1972 LT1 Corvette, 2014 Artic White 3LT/Z51 C7, 2013 650i Convertible BMW, 1994 Kawasaki Vulcan, 1992 Yamaha Seca II and 1996 Dodge Ram 2500. 
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#3
06-25-2013, 05:00 PM
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The 85 has a 2.88 gear ratio so will give a 7% or so taller final drive, so it will give a bit better fuel economy and quieter engine on the highway at the trade off of slightly slower acceleration.
To me the improvement is slight enough I prolly would not change it for that reason, only if there was aproblem with the 307 ratio rear end
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.  [SIGPIC]..I also have a 427 Cobra replica with an aluminum chassis.
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#4
06-25-2013, 07:01 PM
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Interchangeability depends on the ring gear diameter as there are few things that will swap between a 185mm and 210mm differential.
If you posted some photos that would be helpful...
__________________
 Did you just pass my 740 at 200 kmh in a 300SD?????1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013 100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership 
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#5
06-25-2013, 07:05 PM
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Quote:
On my 1978 300SD (W116.120) I went from a 185mm 3.07:1 diff to a 210mm 2.47:1 diff. The best part of the swap was I switched to the 'Lobro' 6-bolt inner CV joints which are very easy to reboot. The car lost some felt acceleration, as one would expect with such a drastic change in ratios, but it was quieter, smoother and faster on the highway. With the 3.07:1 ratio, I could knock down 25-28 mpg (sometimes 30) if I drove at 55-60 mph. With the 2.47:1 axle, I still get 25-28 mpg (sometimes 30) at 75-80 mph. 2.88:1 is about as far as I would recommend going, FWIW...
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Did you just pass my 740 at 200 kmh in a 300SD?????1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013 100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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#6
06-26-2013, 08:26 AM
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Quote:
__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco...  " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod 2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."
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#7
06-26-2013, 10:04 AM
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Its a lot of gear for a 617 to pull below 3000 rpm...
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Did you just pass my 740 at 200 kmh in a 300SD?????1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013 100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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#8
06-26-2013, 10:08 AM
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the axles will not swap between 126 and 123 vehicles...
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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!
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#9
06-26-2013, 11:42 AM
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I'm running a 2.47 rear end in my 380sl with a 617.952 engine and it is just perfect. I can max out mileage at 33.8 (level, no wind, no brakes, steady 70) I'm turning 2400 at 65 so that's very quiet and smooth. I'm a little lighter than the SD, but not that much, and probably a little better aerodynamics. Almost no downshifting on steep grades. Obviously this is a not a performance setup, but I have more than adequate performance for my needs. I don't like to over-stress engines so I keep my max speed to 72.
The 2.47 is great in my book.
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Current Stable
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#10
06-26-2013, 12:06 PM
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Quote:
 My SD is currently set up as a 3.07 with 2600stall converter and its a land rocket. Can launch off the line almost as fast as my 420 does!
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-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)
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#11
06-26-2013, 01:32 PM
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Quote:
It's OK on the usual 2-1 downshift start, but it's definitely not as quick as it was with 3.07's...
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Did you just pass my 740 at 200 kmh in a 300SD?????1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013 100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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#12
06-26-2013, 01:52 PM
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What are torque converter stall ratings and how do they affect power at takeoff?
__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod 2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."
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#13
06-30-2013, 09:04 AM
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Quote:
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#14
06-30-2013, 10:45 AM
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WVO Madness........ the Differentials used in the 81 thru 84 300SD, and the Differentials used in the 300D 82 thru 84 are both 3:07.
The Diffs used in the 85 300SD and 300D are both a 2:88. One Differential is not better in the SD as being stronger etc... they are exactly the same. The 2:47 Diff mentioned is used in the W126 gassers. Differentials used up to 85 can be swapped between chassis platforms, W116, W123, W126. W126 from 86 thru 91 will not swap into the earlier chassis. You could even use a 3:69 240D Diff, you would have good Jackrabbit starts, but would be screaming on the top end. The W126 axles will not work in a W123 because the W126 has a wider track. The Trailing arms and Diff mount will be a direct fit over to a W123. The rear brake Rotors will be a direct fit also. Charlie
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there were three HP ratings on the OM616... 1) Not much power 2) Even less power 3) Not nearly enough power!! 240D w/auto Anyone that thinks a 240D is slow drives too fast. 80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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