NELSON359

I have a 91 foxbody with a lq4 backed with a 4l70 out of a trailblazer SS. I plan on putting a turbo on it soon. So I wanna switch to a 4l80 to hold the power. Would I have to change the cross member? The drive shaft length? Would the computer hook right up? Any help would be great. Looking to get 800rwhp.

Project GatTagO

iTrader: (7)

Yes
Yes
Yes

Andrew

tfi racing

iTrader: (2)

And re-pin the connector,add wiring for the second vss and PCM reflash.Does the 4L80E actually fit in a Fox chassis or is there some sheet metal massaging needed?

EdyJun

I would see about building the 4l70e, depending on power.

Rocketrod

iTrader: (2)

I'm considering a similar build. The big name trans shops, RPM and FLT, say for a mainly street driven car a built 4l70 will hold, but a more track oriented car the 4l80 is the way to go. However I think I am going with a 4l80 as I know it will work, I just don't care for all of the additional changes required: crossmber, exhaust, driveshaft?, ecm, etc....

Unless you have a universal crossmember it will have to change.

Depending upon the year of your 4l70 and the 4l80 the length may not require you to cut your driveshaft. I would however budget for it and assume you will have to cut it. You will need a different yoke.

Depending upon the ecm your using you may be interested in this.
http://www.tunedbyfrost.com/products_dev1.htm

Best of luck.

DailyGTO

My fox had a 5.0 and t5 when I bought it. When I first did my LS swap, I put a 4l60 in, and was able to use an AJE crossmember. I quickly decided to go for a 4l80, and things got interesting. The 4l80 mounts very far back compared to a t5 or 4l60. I called a few companies, AJE, etc for a crossmember, but nobody makes one for a 4l80 in a fox. I ended up making my own frame mounts and using the 4l60 crossmember I already had.

As for the tunnel, I didnt really need to do much hammering. In fact, the 4l80 seems to fit better than the 4l60 did in regards to the cooler lines and shift lever. The only area I needed to hammer pretty well was for the electrical connector. Also, my 4l80 had a tab on the driver side of the bell housing that I had to chop off. Now there is more room that the 4l60 had.

I swapped out the yoke and was able to get away with the stock t5 drive shaft. My 4l60 and 4l80 were the same length. Im not sure if there are differences in regard to your 4l70.

As for electrical, I used an aftermarket TCU that can swap to different transmissions on the fly, so I cant really help you there.

c6matt

iTrader: (1)

I did the swap in my 67 build thread. I found the 80 actually had better clearance than the 60/70

but yes, yes, need wiring but the main trans plug is physically the same, needs slight re-pinning. (easy)