The old tranny didnt like the 300 shot. The very first time i hit the 300 shot; it shifted really hard into third. From there on out i now have no third gear. I think it is time to invest in a 4l80E. 700 hp was ok, but the 800 just seemed to do her in.

I dont know what i am going to do now. I think it is going to have to sit for a while, until the feds start comming in. The thing that sucks is that i never got a chance to get it to the track.

 

I've broken three transmissions with my Magnacharged Tahoe.I've been researching the 4L80E swap,TCI makes a stand alone computer to control the shifts,Yank makes a converter,you need a crank spacer from GM and you need to change the front yoke on the driveshaft.From what I read a built 4L80E can live with 900 rwhp and stand full throttle shifts into 4th gear.The gears in the 4L80E are taller in first and second with a shorter forth yeilding much closer gear spacing.You will need a 4.56 rear end gear to launch the truck as hard as the 4L60E.I've been collecting the parts to make the swap.I hope this post is helpfull.

 

Whitt, I could swear I saw that someone makes a low gear set for the 4L80E that gets you around a 2.60:1 first gear. Yeah it isn't great but better than that 2.40:1. Lemme look around and I'll post up with my findings.

Either way someone needs to take this plunge, the 4L60E is better suited in light vehicle applications and not for all out power.

 

TCI does a low gear planetary 2.75 first and 1.57 second it's worth considering if you don't want to change rearend gears.

 

Well for $508 (Summit Racing) you can get a 2.75:1 first and a 1.57:1 second. Those slighly closer ratios may actually make you a tad faster as they are not soooooo spread like the 4L60E.

I would opt for those when building that trans fo' sho'.

Anyway, are you pretty sure the 4L80 can't be hooked up to the PCM with vehicles that have a 4L60E?

 

The low gear planetary would yeild gearing in first and second with a 4.10 equal to a 4L60E with 3.73 gears like I run on my Tahoe.

 

Well yes 1st gear with the 4L60 will be superior, but the RPM drop off between the 1-2 shift on the 4L60 is huge. The 4L80 with the low gear set will be better than the 4L60 as the ratios are not sooo wide on the 1-2 shifts.

I wish GM made a nice 5 speed auto like: 3.35:1, 2.15:1, 1.50:1, 1:1, 0.66:1 or something comparable to those ratios.

 

GM does make a 5speed 3.45/2.21/1.60/1.00/.76 it's available in the Cadillac XLR and will be in the C6 Vette.But it's brand new with no aftermarket parts available.

 

I do remember reading something about that come to think of it in one of my various car mags. Got any ideas why GM still uses such poor ratios in the 4L80E?

 

You guys suggest that a 4l80 with 4.56's shifting into fourth would be much better than if i just used 1-3. 4.10's are a little to low for me right now. With that tranny set it 4.10 gears would probably be perfect it sounds like. Do you guys think that with the gears i have in it; it would be able to use most of fourth in a quarter. Because right now i really need closer to 3.73's.