best transmisson?

[im4abj]

what automatic transmisson is best for a 454 with 420+hp

[Robs71Nova]

Its all about what your goals for the car are. What kind of gear are you running in the car? And what kind of driving do you do with it. If you are running a steep gear and do alot of street driving, something with overdrive will probably work out well for you. A little more info is needed though.

Rob

[Twitch1]

TH400 can handle it with no problem.

[BullDog71ss]

Yup, the TH400 is what I run. It'll handle gobs of power in stock form.

[Triplet]

Trick question!

There is no "best" transmission. You can build just about any transmission to fit your needs. Some have weak points, some have strong points. I currently run a th350 in my monte carlo with a 454 with a modified version of the gm 454HO crate motor. The motor from GM is rated at 425 hp, and has been dyno'd at 465 hp stock. I have changed intake and cam. Being in a heavy car is also hard on transmissions. A friend of mine (and the guy who built my transmission) runs a th350 in his 10 second camaro. Th400s are fine, but they rob a little more hp than the 350. 400s in stock form are a little stronger, but with any trans, if you plan on abusing it a little (who doesn't) you shoudl ask your transmission builder about what hardened races/sprags etc you might want to add. The 700R4 overdrives are notoriously weak in stock form when you apply lots of torque. The 4L80E is an excellent and strong choice for an overdrive trans that can take alot of abuse, but they are really heavy and need a computer to control them.

So. . . If your transmission guy is familiar with building strong transmissions and how to modify them to handle torque, then I recommend the 350 so you save some horsepower loss. If they are the type of place that rebuilds things stock only, then I say the th400. If you need an overdrive and have lots of $$ , then the 4L80E is great. You can also build a 2004r if you want an overdirve, but they can get pretty expensive and need to be modified fairly heavily too.

There will be people who tell you that either the th350 or the th400 or some other transmission is the ONLY way to go , they are just misinformed and wrong! Sorry guys! There is lots of good stuff out there and you can make most of them work for your application.

Good luck!
Scott

[nova68]

a built 350 is what i have sweet!! you dont really need a 400 I would get a really soundly built th350. thats my two cents worth

[Ground Rat]

If I had the money I'd swap out my TH400 for a 4L80E which is basically a TH400 w/ an overdrive. You can get a built 4L80E that is not electronically controlled (does not need a computer).

http://www.transmissioncenter.net/4l80e.htm

[Triplet]

4L80s are too $$$$$$$$$$$

[MrPbody]

As a "high torque" engine builder, a transmission with an "anti-clunk spring" always made \me a bit nervous. It's true, TH350 can take some abuse. It's also true, TH400 is FAR superior.
Another issue not discussed here, is the power flow through a transmission. Most automatics will require two events to make the 1-2 or 2-3 shifts to happen. TH400 only requires 1. This is the primary reason for the popularity of TH400 in race cars. TH350 can offer some slight advantages in gearing, especially first. It is universally accepted that PowreGlide is best in a lighter car, and TH400 in a heavier one. TH350 falls in between.
For OD units, there are pros and cons to ALL of them. We've found TH200-4R to hold up better behind big engines than 700.