4L80E Questions

[Old Car Guy]

In various of the threads that have discussed the 4L80E transmission, there has been mention made of how inefficient they are, in terms of how much HP they soak up.

If the 4L80E was developed from the Turbo 400, which is what I've read, does the 4L80E eat up even more HP to drive it than does the Turbo 400? The Turbo 400 is not exactly thought of as an efficient transmission itself, so have things gotten even worse with the 4L80E, or does it soak up about the same amount of HP as the Turbo 400?

Relative to gear ratios, I've read that the 4L80e's overdrive ratio is only .87, which is not that much of an overdrive, but I guess it beats none. But what about the other 3 gears? If the 4L80E is derived from the Turbo 400, I'd expect the ratios to be those of the standard Turbo 400 - 2.48, 1.48, and 1.00. Is that correct? Also, would any of the Turbo 400 wide ratio gearset technology (2.75 low gear) also be applicable to a custom built 4L80E?

Finally, assuming I wouldn't find it inconvenient to shift the thing manually, could I get one set up to be street driveable, or does a full-manual setup also require doing things to the tranny that would make it too much of a pain to drive on the street (besides the manual shifting requirement). I don't know whether or not a full manual setup requires a high line pressure to function properly, but I do know that if every shift I made was going to hit like I was at WOT, that would not be acceptable to me.

Thanks in advance for any answers I get.

 

[chris718]

ratios in 123 are the same and the trans does eat up more energy because you have to drive thru the o/d clutches and od planet in 123.the 400 hi lo gears will work but the rear planet must be a moified 4l80e or a 400 modified to put the speed sensor wheel on its outside diameter. gm makes a computer for all non factory applications and custom shift programming is done thru a laptop.you can also shift manually with certain kits.but this trans is very heavy and if you are looking for an o/drive trans for over 700 hpower with durability ,less hp drain ,and no computer check out our aod trans for gm applications .in the 8 second zone and still staying together w/ cars at 3200 plus pounds.

 

[Old Car Guy]

Chris,

Thanks for the response. Now let's see if I properly understood what you told me.

The 4L80E will eat up more HP than the Turbo 400.

The standard gearing for 1-2-3 in the 4L80E is 2.48, 1.48, and 1.00, just like the Turbo 400, but the wide-ratio Turbo 400 gearset with the 2.75 1st gear would be an available option in a 4L80E.

I do understand that the 4L80E usually uses an external computer to control its shifting, but that makes things VERY expensive. In a previous thread, someone commented that the 4L80E could be run as a full-manual-shift transmission, without the computer (and its attendant expense), so long as you didn't mind the shifting effort involved. So that's where my question about manual shifting came from. I guess I was really asking whether the 4L80E would deliver properly modulated shifts based on throttle position if set up to work as a full-manual-shift transmission, without an external computer. I am assuming the use of a non-lockup converter. If the previous poster is wrong, however, and the 4L80E cannot be set up that way, my question doesn't make much sense.

You and most everyone else comment that the 4L80E is a heavy transmission. How heavy are we talking about here?

About the AOD, I don't like the AOD because it will not shift into overdrive at WOT. I consider that nothing short of a design flaw. So I guess I'd better ask, will the 4L80E allow for WOT upshifts into overdrive?

Thanks again for the info.

 

[jakeshoe]

Old Guy,
You can make a full manual from a 4L80-E.
TransGo makes a kit to do this.
It is a heavy trans, around 270-280 with a converter I believe. Converter is about 70-80 lbs...
The TransGo kit is about $200 wholesale so you would be better off to use a $600 brain and have auto functions and a lockup convertor. It's 400 bucks but it will save you that in the long run.

 

[2quiktocare]

What type application are you planning or thinking of using this trans in? That would be my first question. Anything more would be based on that (unless I am blind, a distinct possibility) I didn't see what it is in. Your question could be better answered if we knew what perameters you are working in. Is it a conversion or an O. E. application? Let us know,,,,,,,,,,thanks, Mark

 

[chris718]

the trans go kit is junk.billy denali in philadelphia makes the best full manual kit ive seen.it has an adjustable line pressure control kit that mounts to the throttle body or carb.all 8 of our turbo 4oo ratios will work in the 4l80e as well as all the other th400 upgrades.and a final note our aod WILL shift into overdrive at full throttle with the stage 2 valve body .this has a new 3/4 shift line that makes this possible,as well as other mods .look around and see how many 8 second mustang renegade cars are running ck aods if you are questioning reliability.and im not being an ass boys but it will run circles around a 2004r as far as strength is concerned.the real 8 second o/drive trans.

 

[jakeshoe]

Chris,
What's wrong with the TransGo kit?
I agree that if a kit is available to have modulated line pressure via a TV or similar that would be a better setup.
Full pressure all the time isn't good.

Any other problems with the TransGo?

I haven't installed one in a 4L80 so I wouldn't know anyway just curious.

 

[Old Car Guy]

Chris,

Thanks for replying again.

I never questioned the strength of your AOD's, but I was not aware that yours would shift into and hold overdrive at WOT. Congratulations on making that happen.

I had always thought that the overdrive clutches in an AOD were simply too small to hold an engine's full power without burning up. Looks like I was wrong.

 

[chris718]

the aod uses a band for o/drive and if you install the aode/4r70w wider band shell and drum you got an unbeatable combination.also the late code a servo squeezes the band just right.about the transgo kit it shifts long and bangy and uses the band in manual lo so you get a real long 1/2 trying to knock the band off at wot.they didnt do their homework.for stock cars and trucks they are well conceived kits but for ho engines they just dont work right.look at the mess they made with the 2004r /2 kit .