Posted by Charlie on November 30, 1999 at 00:45:41:
In Reply to: Re: 6 speed is gettin' better<---BULLSHIFT! heehee posted by David on November 29, 1999 at 23:19:57:
I grew up in LA. I figured it was time to leave about 28 years ago. fortunately, many of us, including me, live in areas where we can drive to work during "rush hour" (Anchorage DOES have traffic) in not only a stick shift, but a non-synchro crash box.
Most of these diesel trucks (for example, a M37 or PW repowered with a 4cyl diesel) need an overdrive gear to be able to cruise at 65-70 in an economic area of the bsfc/rpm curve (bsfc = brake specific fuel consumption = lbs per hp-hr), also need at least 3 gears below it for normal driving up to 50-55, and a granny gear for offroad work or steep uphill starts when loaded. That makes a 5 speed. But the 1.70:1 ratios between 3rd and 4th and even bigger between 2nd and 3rd drop rpms down to 1650 on a 2800 rpm motor (Perkins, Hercules) and down to 1450 on a 2500 rpm motor (Cummins). A 6 speed of course has tighter splits and that's just what is needed for a diesel with a low peak hp rpm. The only alternative is to use a conventional very wide ratio 4spd with a separate splitter/overdrive which allows splitting 3rd gear, which is the main problem.
These 6 spds will become valuable conversion material. If anyone has one and doesn't want it, I'll happily take it off their hands, I'll even pay the freight.
I'm waiting for the 7 and 9 spds.
Charlie