I have Th350 and 411s and my plan is to put a 4L80E in before I change gears . I don’t want to drive on the interstate at 80 mph. I want to spend my time driving back roads and enjoying the drive. I’m not sure it’s worth going to 373 from 411 I dont know if it’s a big enough of a change to justify the cash
I wonder if you're going to see a whole lot of benefit? Why the change then?
To get a good 4l80e ($1000+?) costs for to have it gone through ($1000+?) a controller ($1000+?) costs related to crossmember, mounts, fluids ($500+?) You're probably above $3000 plus time to install a unit that draws a bit more power and weighs more.
But you aren't interested in highway driving at speed which is where the OD kicks in and saves gas mileage.
To cover costs of install. Everything else being equal, you'd need to save about 1000 gallon of gas as well.
Crunching the numbers in an arbitrary manner, lets say you jump 16mpg to 20 mpg. So that 1000 gal represents needing a savings of 20,000 miles. At a 4mpg savings per gallon, you'd burn 5,000 gallons to get that. And 5,000 gallons at 20mpg again means driving 100,000 miles before break even, and, that doesn't account for time/value of money, inflation, interest/appreciation you could get by investing elsewhere...
End of the day, in a back roads corner carver the OD benefits aren't there compared to a cheaper th400 unit. And to break even if the motivation is to save gas it takes a LONG time for OD to pay off..
If your concerns were too high rpm on highway there's a benefit beyond savings.. or you blew a trans and needed to buy something because you have nothing right now the analysis changes. Then it's the cost difference between 3spd and 4spd you need to save to have it pay off.