Trans suggestions for 2nd gen Ls3 Firebird ...

[cpd004]

I'd like opinions on running an auto trans behind my 2010 Corvette Ls3 in my 71 Firebird. I'd love to go 6L80e like I have in my G8 but I understand it requires some mods (although there is at least one person running one stating he didn't need to do any cutting).

The main purpose of this car is for Power Tour, car shows and all around reliable daily driving. I prefer a firmer shifting car and I'm currently running a 3.42 rear. The engine is stock other than a tune and headers.

Interested in opinions for a donor car. I already have a PSI harness (15 pin) and trans controller. Seems to be a bunch of options out there and have no idea where to start.

[armourmark]

Depending on future mods, I would look at a 4L80, 4L60, or 4L65. All are nice 4 spd autos and your 3.42 will be loafing at cruising speeds. You might consider the 4L60 as it has a steeper first gear vs a 4L80.

[cpd004]

So would a trans from a 2008 Trailblazer 2wd be a good donor? I ask because I have several of these available locally. Best I can tell is that these are 4L70e's.

[csouth]

So would a trans from a 2008 Trailblazer 2wd be a good donor? I ask because I have several of these available locally. Best I can tell is that these are 4L70e's.

I will tell you that the 4L70E has 2 different pin outs depending on the year with the 2009-10 being the change year. It is a good transmission. TBSS guys have complained that they are weak, but guys are trying to drive a 4600lb vehicle like a Corvette just because it has an LS2. That will always cause problems.

[cpd004]

Thanks for the info. Only other thing I've read is they're a soft shifting transmission.

[srh3trinity]

Mine is going to have a 4l80e. I would assume whatever you get will be rebuilt and I think you can do some things with tuning to firm up the shifts.

[cpd004]

There are many low mileage transmissions available locally. I was hoping to be able to find something I can just swap in without a rebuild but am not sure if what I'm finding will work with the PSI harness and Trans controller as well as the ls3. The high mileage ones seem to be from Tahoe's with the 5.3 and police package. I will have whatever I find rebuilt so I dont have to do twice the work.

[csouth]

Do you have the TCU harness already? I'm assuming you know that the 4l80E has a different connector than the 4L60/65/70E? Has the TCM been programmed? Take a look here....

https://www.powertraincontrolsolutio..._Reference.pdf

As said above shift firmness is a product of the internals as well as the tuning.

[cpd004]

csouth...thanks for that link!

[csouth]

csouth...thanks for that link!

No problem. I would just hate for you to be all set on installing a 4L80E if thats your choice only to find out the harness wouldn't work as is. There are a couple companies the makes a 4L60E to 4L80E conversion harness if that ends up being your choice.