Quote:
Originally Posted by 777funk
Not to change the subject but while we're having trans talk, What about this thought...
I wouldn't change one thing on the engine of my 300d. However the car was designed to travel at 55mph not today's highway speeds of 80 in some states. The MPG would be better and get the RPMs down if it had a modern transmission. Anyone put an Overdrive Tranny in a w123? Mines great! Just doesn't shift into 5th gear like I wish it could.
While you're changing the trans maybe the thought of updating? I don't know but I do know if mine went I'd really be doing a search on it.
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I agree with you. Many rear differential swaps have been performed with the idea of better highway performance due to lower RPM's. 3.08's swapped for 2.88's and 2.47's. The results have always seemed worth it to the owners despite claims of "lugging" the engine or reduced performance at lower speeds.
The arguement is made that these are high-speed diesels. Yes, they are in a relative way. The reality is the torque curve is pretty flat so changing gearing modestly has no noticeable effect on performance but helps drastically at cruise speeds by lowering RPM.
I have read a bunch of literature and seen it said time and again that a diesel engine should be geared to spin at its torque peak while cruising. That last time I checked that peak occured at 3100-3200rpm on the 617. Sure you can spin the engine faster with no ill-effects but why would you if there are alternatives?
Look into the Volvo 5speed. It would be nice to find a bolt on manual that is not so rare as the MB trans. If I had the money I would be trying to get a Borg Warner T5 or Tremec to bolt up. The B&W is so common in 5.0 Mustangs and a very nice shifting trans. I would imagine that a modified MB bellhousing, custom clutch/flywheel/input shaft would be required. The domestic performance clutch suppliers can do this stuff but its not cheap. Unfortunately.
RT