Get a "Built" 4L65E. I've been running 9#'s of boost on my 5.3 in my 5600 pound Tahoe and I beat on it daily, no problems. I put it behind the 6L last week. We'll see how long it lasts. Get a level 5 4L65E from FLP. I really should have an 80E but I refuse to accept the gearing. Just make sure to get a good one, not an ebay special, and you should be fine.

 

I like the points that are being stressed about the gear ratios of the two trannys i like the idea of the 4l65e but the price on that thing is $2850 is it worth that much, the 4l65e will bolt right up no mods needed correct. isnt the 65e just a stronger built 60e? by the looks of it these trannys are strong i see one that is holding 725rwhp and claims to be as good as it was when it was first installed that makes me lean closer toward this tranny.

 

Yes, it will bolt right up. $2850 sounds high until you think about replacing a 4L60E a couple of times and all the labor and/or time involved. You can find on cheaper but check into the shops reputation. Or find a local tranny shop that will build you one and warranty it for what your setup will put out. They could upgrade your stock 60E cheaper but if they wont warranty it, forget it.

 

Thats the whole point man, you DONT spin the tires, why sit at the line spoinning when you can be accelerating? In a 2wd anyway, even though the high hp trucks even in 4wd still have traction problems.

With a 3.06 1st gear and 4.10 rear gear the final ratio is 12.4:1, with the 2.48 80e 1st gear and 4.10's the final is 10.17. You can make an 80e launch just as hard as any 60e with the proper TC and still hook, and have the preferable gear ratios for dragracing.
Actually the 80e has the same 1st gear as the old th400's do, you can only get the 2.75 gear AFTER you install an aftermarket gearset. The 80e has a 2.48:1 1st gear ratio, the 80e will cut a slower 60ft, but will be quicker in the 1/4 mile, with less rpm drop between the gears, this is the whole premise of a close ratio trans. The 60e feels faster, but thats only because of teh 1st gear ratio, in 2nd and 3rd there is no advantage. The 80e is a superior trans for high power levels and drag racing. I would rather have a 200r4 than a 4l60/65/70e any day.

All things equal, a 80e trans will have superior traction. These transmissions dont use THAT much power. Anyone with a real engine can spare a few hp thru the trans for traction and reliability.

The 65e is just a slightly improved 60e, as the 70e in the TBSS is just an improved 65e.
The 60/65 might be ok in the lighter f-bodies, but in any truck with high torque and power combined with a 4000 lb or higher weight, will benefit from a 4l80e/85e trans.

I dont care who built it, a 60/65 wont last long at the 725 rwhp mark, thats 870 hp at the crank, justy ask Parish.

I guess in the end it really does depend on what the exact combo is. For high power drag racing, the 80e cant be beat. I have seen way too many 60e/65e transmissions supposedly built for 700 hp, take a crap in trucks with maybe 450 hp. Swapping high dollar transmissions get expensive quickly, when I get the money, I will be dropping in an 80/85 and be done with it. $3000 here, $3000 there, I get really tired of that quickly. I would rather do $4000 once, IMO.

peace
Hog

 

I think you fail to realize the physics involved in gear ratios and launching. Not spinning doesn't mean launching well.
You also contradicted yourself unless 10. 12.4 = 10.1 ?

If you really want an explanation,I can give it but its 2am. Take my word for it. You can launch much better with a steeper first gear ratio and it will also be much nicer on the drivetrain

725 rwhp is such a rediculious number to throw out there.

I see no indication of anything much above 60% of your number. You are almost DOUBLING out output. No argument that at those power levels, the 4L6X is a poor choice.

 

Man this is going to be a hard choice to make. I know the durability of the 80e its a beast. I guess im going to do some more research and take some more pointers from you guys before i make any choice. Has anyone here put an 80e into there rcsb silverado 2wd if so what is there to modify just the crossmember and drive shaft, and get a wiring harness for it? when i get my swap complete i will be happy running 12's even if there high 12's this will be a daily driver and i really dont want to devour my mpg do you think 12's are possible with my truck with the 6.0 and a magna charger and of course a custom tune headers and exhaust? if not what do you think i will need to add to my list to accomplish this task. IM in no hurry when i do this i want it to be done right! Also which gear ratio should i go with.

Thanks for all the help, yall are making my life easier. i appreciate it.

 

Let me tell you the BIGGEST mistake made by do it yourself types in performance build ups

buying parts before setting a goal.

SET A GOAL
Then choose the parts.

If you want a 400rwhp truck- then take a 4L65E
If you want to make 750rwhp- you need a 4L80E

Its amazing to watch people buy heads, cam and then hope for a number. "well with these heads and cam and this blower, i'm hoping to make xxx hp"

no, it should be

"I'm aiming for xxxhp and thats why I am running ....."

Set a realistic goal, aim, pull trigger, hope it stays together

 

Aint that the truth!

 

I have to agree with this
Ive seen so many posts about breaking 4L60s
but they can be built
so I tried to learn from everyones mistakes and ended up with FLT
I chose the FLT level 5 because of Chucks background and accomplishments

FWIW I researched long and hard on this and talked to several
of the guys on this site that makes big #s
and knew this was the correct direction to take

my .02 cents
great guy
hell of a transmission
give him a call

 

I was thinking "duck for cover" but figured that was less ambigous