4L60E to NV4500 5-speed ?'s

[aardvarcus]

I did a 4L60 to NV4500 swap in my 1991 K2500LD pickup truck, RCLB, 5.7L, 4x4, and 3.73 gears. I went from getting 12-13 highway MPG to getting 15+ and eventually up to 18 highway MPG. The manual transmission allowed for a much better driving style. My swap is documented on this site, buried somewhere in threads of yesteryear. The transmission and therefore the driveshaft length is the same between them.

That said, if I had a 2wd, I would take a hard look at a T-56 or a TR-6060, especially one with a 0.50:1 overdrive ratio.

[oil pan 4]

The t-56 has top gears of 0.6:1 (the more common ratio) and 0.5:1 which is kind of rare.
I think swapping an auto with a 0.7:1 top gear for a manual with a .75:1 top gear just won't give you the gain's you are looking for with out also doing a rear gear change.

You can do some light towing rear. My firebird, has the 7.5 inch 10 bolt rear and I tow with mine, only about up to 800lb.
But eventually I will roll a ford 9 inch up under there.

[gumby79]

7.5 is avaliable down to 2.73 ,and a 3.08
https://www.strangeengineering.net/p...2-series.html/
3.73 auto. 2.573 stock.
3.08 auto 2.125.
2.73 auto 1.883..,.,. Would be about 1413rmp at 60mph
Auto
3.73 to 3.08 =13% reduction in over all rpm for gear change
3.73 to 2.73 = 37

3.73. 2.798.
3.08 manual 2.310.
2.73 manual. 2.04,.,.,.,.,., would be about 1533 rpm at 60mph on215/70R 15 tires

3.73 to 3.08 =17%reduction in over all Rpm for gear chang
3.73 to 2.73 =34%

The manual with its compound low will help with the 2.73 (tall) rear on take off.
2.72 If the auto is week this could finish taking it out.
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Assuming you have the 4.3 Vortech the 4 speed with 2.73 out of a 77 nova may be an option.
If your in flat terrain 3 speed Saginaws have been known to get good mpg . My experience 250ci I-6 3speed 2.73:1 =22-26 mpg on a stock 77nova .
My grand mother went from 18-23 down to 12-14mpg on her 1961GMC1/2 ton c10 with the 305 V6 by swapping the 3 speed for a SM420 (7.05 1st compound low) the extra mass from hevyer duity gears made the difference.
Dreem big chisel down to reality