" One of the most reliable ways that can be done is to reduce engine " rpm at cruise speeds. This can be done by adding a 5th gear as an " overdrive to an existing 4 speed transmission. 4th is still 1:1 for the " most part but 5th will be typically in the area of .75:1 or so. Why that " number I don't know as real overdrives were typically 33% or so. " Maybe perhaps that is all the room they had in the transmission to " put gears in to. the warner r10 o/d is 0.7:1. ----- The Borg-Warner R-10 also reduces engine rpm by 33%, and the ratio is indeed 0.70:1. The entire drivetrain (engine, trans and ratios, rear axle ratio) has to be matched for best overall performance. Manufacturers make some compromises for us, of course. When a drivetrain is modified it becomes harder to find an inexpensive combination to match everything back to a reasonable compromise. It's either spend the money or compromise the drivetrain even more. I agree with Andrew on this one only because drag racing appears to be more important than cruising, so the top loader four speed will be the better deal. That is unless he wants to spend the dough for the Tremec. Another solution might be to use the top loader now, and buy a Gear Vendors OD later. -- Frank Swygert Publisher, "American Motors Cars" Magazine (AMC) For all AMC enthusiasts http://farna.home.att.net/AMC.html (free download available!) _______________________________________________ Amc-list mailing list Amc-list@xxxxxxxxxxxx http://www.amc-list.com/mailman/listinfo/amc-list