Quote:
Originally Posted by t walgamuth
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...
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This may help you...
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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