swaping th400 for a 4l80e

[jp0863]

Tried the search, ony pertinent 2 i found were both diesels. My questions are mainly, is it worth it? I plan, once it's built, to drive the suburban a few times a week. Most of the driving will be in town, under 55 mph and the occasional out of town wheeling trip.

Currently I have a 5.7/th400 with 4.56 gears and 35's. It is not driveable at this point so I have no base line numbers for mileage. To get it driving will require a transmission rebuild, which is why I am contemplating the swap now before dumping money into the th400.

For around $650 I can have the th400 rebuilt with kevlar clutches, allison t/c, and a valve body built/modified for heavy duty/towing use.

Only reason I would consider a 4l80e is first, it's free. Would still need to rebuild or at least go through it, plus stand alone computer.

For the slight mileage gain, would it be worth it.

 

[sweetk30]

read this http://coloradok5.com/forums/showthread.php?t=166233&highlight=4l80-e lots of info .

and play with ratio rpm calc here to see rpm diffrence http://www.grimmjeeper.com/gears.html

and simple way to make 4l80-e run on elctrics. http://www.usshift.com/index.shtml

its longer than th400 tranny. so drive shaft work needed.

i run a k30 now with 350tbi/th400 and 4.10 gears and 35" tires. i tend to be 3k rpm at 65ish . when the truck gets redone it will get the 4l80e i have fresh reman in stock with 1 year only 4l80-e to 205 adaptor i have.

not best to tow in overdrive anyways so there is the toss up for you . and if no long hauls then cost to benifit = not the best.

and same gear ratio's in both trannys.

 

[454Sub]

The stand alone is pricey from what Iv seen. I plan on doing the same thing, trying to find a cheap 4l80 to np205 adapter now. On mine, since its a 90, i got a complete wiring harness and computer for a 91 with the 4l80 and just going to swap that all out and do it that way, the standalone doesnt really fit my needs as I mud mostly and its another computer mounted that could fry leaving me stranded, where the stock one is behind the glovebox and would be tough to get wet. I love the tranny though, I have a 454/400/205 with 5.13s and 40s and i turn around 2700 at 60ish, my brother has a 6.0/4l80/241 with 4.10s and 40s and his feels much much better, no tach though, he just doesnt have the low end I do.