Quote:
Originally Posted by t walgamuth
cool project. It won't be a 40 mpg vehicle but it has the potential to get better fuel economy than the truck the diesel came with if the rear end gear is chosen for economy (I'd recommend a 308 to 330 or so rear end).
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Although a 3.08 would be very drivable in this setup, if this is actually as light as I think it might be I would recommend a 5sp NV3500 granny gear xmsn (make sure you have the granny gear or it is irritating like my suburban)
Then couple to a 2.5-2.83 rearend.
The 6.2 drives just fine near idle assuming your aero and weight put you into the sweet spot, there is a nice chart for the 6.2s max HP from 1000-5000rpms somewhere around here, if you could get a rolling chassis setup and figure out your goal speed and how much power it takes to push it you can determine your ideal overgearing setup so the 6.2 puts out just a tad more power than you need or you can put it spot on and just let the thing speed and slow and downshift to take off.
Just make sure if you do this (which I did in my heavier suburban) that you detune the 6.2 so it has a low enough IP pressure so it doesn't smoke near wot at low RPM. You may also want to adjust the static timing because contrary to popular belief it isn't ideal near the extreme RPM ranges of the motor.
My suburban is rather odd in when I can shift with the 2.73 rearend, in town I can drive in 5th gear idling just fine, on the highway I need to stay in 3rd or 4th up to about 65+ before I can enter 5th reliably depending on a variety of factors (terrain being one), I think I could solve this issue though if I fixed my IP pressure and the persistant fuel leak and the messed up throttle.
Good Luck