Ok. I'm looking into getting a 408 with a 150 shot and I was wondering if the stock 4L80E would hold all of that power or if I would have to get a built 4L80E since i'm going to be pushing a lot of power. Thanks for your help. Also what kind of cam do you think I should get for the setup. I was thinking about a X1 cam. 230/227/.591/.591/112

 

Parish8 ran a 10.9 on a 4l80e with a shift kit, although I think he busted it about a month ago....

 

There are a few angles on answering that...

First, the 4L80-E is only rated for a maximum shift RPM of 5200. The main reason for this is the use of conventional friction materials. The higher the shift RPM is the more RPM drop difference the clutches have to overcome which leads to more heat. The hard parts are capable of moving the torque without a problem. I would not expect the stock clutches to hold up for long, they should be upgraded to something more capable like Alto Red Eagle or similar. There really aren't any exotic clutches available for overdrive, so that needs to be considered when programming the 3-4 upshift.

With that kind of power you need a shift kit like the TransGo. It includes a new boost valve and recalibrates firmness based on the desired level. It also includes a relief valve that will prevent damage from over pressure. This is helpful to have when running over its rated limit.

The bottom line is that it will not break with that configuration, but at minimum a shift-kit should be installed to keep the consumables from wearing out or failing too quickly.

 

sounds like the same discussion we had.

 

A shift kit would be a minimum, and it must be a TransGo kit. Most shift kits try to be "race oriented" and all they do is block off accumulators and bypass other systems which can shorten the life of the transmission and cause akward and overly harsh shifts. TransGo Reprogramming kits will give you the firmness your transmission NEEDS as well as fix many of the quirks associated with the transmission which will not only prolong the life, but give you enhanced performance. I'm not a TransGo rep, but I use TransGo in ALL of my tranmissions and I'll only use TransGo.

 

 

So I need to build my tranny then for all of that power?

 

A high-performance clutch pack for the forward piston will help hold the torque. High-performance clutch materials for the Intermediate and Direct will shift more torque for the 1-2 and 2-3 making less heat. These three clutch sets will greatly improve the 80's torque and RPM handling.

There are plenty of high-performance aftermarket clutch packs to choose from for the 80 because those three sets are basically the same as the TH400. Unfortunately I haven't found a high-performance alternative to the overdrive clutches for the 4L80-E. For this reason a fully-built 4L80-E is capable of safely shifting a great deal more WOT torque and RPM on the 1-2 and the 2-3 than it can the 3-4. With high horsepower I would set up the 3-4 to shift at a lower RPM to prevent the OD clutch pack from overheating. For racing I would suggest running the trans in "3" instead of "D" to avoid that shift entirely.

-James

 

James, I have been following a few of your posts and you seem knowledgeable on trannies. My '80 only went about 500 miles under my foot and the 4th clutches were smoked. I have since refrained from full throttle 3-4 shifts-only did it once on the new trans so far. Otherwise it seems to be holding up well. I spray it through the 1-2 and 2-3 and in never even notices.

 

With the power you've got I can see how that could happen. That's a bummer. The good news is that the overdrive clutches are easy enough to get to that they can be changed without even dropping the pan. The front pump, input shaft, and overdrive roller clutch assembly come out as a unit.

Like this: Pump and OD pic

There is a gasket in there that will need to be replaced if damaged:
Pump Gasket Pic

The OD clutch pack is held in by a snapring and backing plate visible here:
OD clutches and Forward Drum Pic
OD Snapring Pic
OD Backing Plate Pic

This fourth clutch is conventional paper, these one the ones in my 80:
OD Clutch Friction Plate Pic
OD Clutch Steel Plate Pic

If anyone finds some exotic-materials clutches for the 4L80-E overdrive please post the source here. I'd like to change mine.

Thanks,
-James Bertok