Need a modern automatic for my 69 Firebird

[anguilla1980]

I'm putting down 1,000ft lbs at the wheels (w/250 shot of NOS to get there) and I'm looking at putting my numbers matching TH400 into storage and going with a 4L80E so I have an OD and lower RPMs on the highway driving to the track and to car shows. I've been told a 4L80E will fit into a 69 Firebird with only having to hammer the trans tunnel for the cooling lines, new crossmember/mount, and shortening the driveshaft about 3".

I also want a trans-brake but would like to retain the automatic valve body and not go reverse valve body either.

I had come here to ask what the top vendors are for such a beast at that power level, which I still would like to know....... but then I saw threads about the 6L80E and now I'm wondering if those will physically fit the same as the 4L80E. It sure would be nice to have a 6-spd for acceleration, but not at the cost of cutting the trans tunnel on my numbers matching car. Hammering I can deal with lol.

Thanks!!

Alex

[Craig@Bowler]

Alex,
The 4L80E would definitely be your best bet. We can build you one that will handle the 1,000 ft/lbs of torque you're making and add in the trans brake if you want that. All things equal it should fit into your car with minimal modifications. The "hammering" is usually isolated to the passenger side of the tunnel where the cooler fittings connect.

The 6L80E is a great transmission, but at this time there aren't a lot of aftermarket performance parts to get it strong enough to hold the power you're making. We've seen them hold 650ftlbs pretty reliable, but anything past that is a gamble. It will also require you to modify the tunnel to get it high enough to where you're not going to drag the pan off the bottom. The other downside is that right now it will only work with the LS engine ECM. So if you're not running an LS engine it won't work since it doesn't have anything to "talk" to. We should be seeing some new controllers on the market in the near future that will allow the 6L80/90 to work as a stand alone.

If you are interested in getting a quote on a 4L80E just shoot me an email [email protected] and I'll put something together for you. Thanks!

[Schwartz Performance]

6 speed is much larger. You'll need to cut the tunnel.
8L90e shifts even better and isn't too much bigger than the 6, they hold up to some serious power on the new cars.

But in your case just stick with the 4L80e.

To go along with what Craig said, have them build you a bulletproof 4L80e!

-Dale

[anguilla1980]

Good point on the controller, I hadn't checked if the Holly Terminator EFI TCM works with the 6, thanks for answering that question that none do but the stock ECU right now.

Thanks again for the responses, when I'm ready to buy in a couple months I may reach out. Until then I'm doing my due diligence on the various vendors/offerings and options.

Alex

[andrewb70]

Alex,

The 6L80 transmissions have the controller built into them. The Holley Dominator will only support the 4L60/65/70/80 etc., and some Ford junk too.



Andrew