I am building a Pontiac firebird and I am going to put a 6.0 stroker to a 408 and I don’t know what transmission to go with I plan to put nitrous on it soon and a turbo later on and it’s looking like I will have around 500 hp. I want to be able to drive this car on the street and race a little bit not really daily it.
Edit: I don’t have a 4l60e I’ll I have is a frame and body so I am looking to start from scratch

 

At 500hp a good 4L60E would work just fine, but if nitrous on top of the 500hp I think a 4L80E would be better. Especially if you don't have a trans yet and are starting from scratch. Nitrous is hard on parts.

 

I'd echo this

 

would I be fine with a stock one or should I get a built one

 

Someone besides me would be better at answering this question.

 

Build it now is my vote. You can have it done with a dual feed direct clutch and not have to worry about it. A good used transmission is just that used...

 

4l60e...100% should go with a performance oriented unit

for the 4l80e...you'll get mixed reviews

As someone who's torn down LOTS of 4l80e cores...and done everything from stock pickup/box van rebuilds up to 1500hp builds...I can tell you that alot of cores are junk
Alot of guys on here will reassemble junk not knowing its junk or just not caring.

The 4l80e is a great unit but when you get a core with 100k miles...it needs alot of work to be a proper transmission even considered for performance use in my opinion.

Now...if you just want bare minimum and cheap and don't care about having a failure and needing to fix it...sure...there are stock 4l80e out of pickups in the wrecking yard that will survive in your car. Probably even with nitrous.
That doesn't mean it's a nice piece

 

My vote is to keep the 4L60E, but if stock you may run into issues as you will be on borrowed time.
You can run a street/strip build and be fine for a long time with that power level, will cost about $2500 but is well worth it. I recommend Finish Line Trans, as I run their L7 4L60E in my twin turbo car.

 

If it survives why would you need to fix it?
If it survives why is it not a nice piece?

I may have just been lucky but ive ran 2 unknown junkyard 4l80e's without doing anything more than a filter and fluid change with no issues as of now..

Honestly just wondering what I need to be looking out for??
Thanks.

 

You can make it home on a spare tire...doesn't mean it's right

but by your logic...the spare survived...so why ever swap it out?
if it survived...it must've been a nice tire!

If you've been inside junkyard cores...no self respecting person would slam it back together with all of the fails inside of it.
To be completely honest...even the most cherry 4l80e core...kindof sucks for performance use. GM left a whole lot to be desired.

 

So what would be a deal breaker on a core for it being buildable or not?

 

Anything is rebuildable, short of a damaged case that cannot be repaired, as any internal component can be replaced and these internal components are all available as refinished/new in most cases. It comes down to knowing what exactly to look for especially when inspecting the hard parts. There are common areas of wear and there are not so common areas of wear. Both are important. Watching a rebuild video on youtube and putting in all new parts while keeping the hard parts the same and not properly inspecting them is a common mishap. There is no rebuild video available that goes into all all these details. The knowledge is obtained over time through personal experience, discussing with those that have torn into 100's of cores and rebuilt them and know the failure points, having your stuff break and having to take it apart and see what you overlooked, etc.

For example, someone may look at a set of gears on a planet and see that none of them are chipped and assume that the planet is good to go when it may not be if there is too much play in the gears. Or they may have a forward drum that is not useable because the sealing surface is junk and needs a new sleeve/replacement. Or they may have a center support that has an issue with how it's aligned apart from the orientation of the bushing, or a pump may have too much clearance between the crescent and the gear, or the vacuum on a circuit in the pump or valve body may be too low. The list goes on and on.

 

You can build a 408 with over 600hp N/A before adding nitrous.

 

yes but I want to run pump gas

 

You can get 600hp with a 408 on pump gas if were talking flywheel numbers.

 

well I hope just going off of what my motor builder said

 

what heads and cam will you be running?

 

not exactly sure on cam yet but gonna port some 317 from the 6.0