Originally Posted by DblTrbl
After searching through a number of boards, I found that there was a ton of information about modifying these transmissions. I found that some guys who are in the business, provide some info, but most of the time they are vague, incomplete or meant to scare people into not working the the trans themselves. Then there were a few guys who were knowledgeable and straightforward that gave what I felt was clear guidance, ideas and photos. Based on exhaustive search through their posts, I'm doing the following mods to get my trans to handle about 1000hp.
The two most important mods appear to be to dual feed the direct clutch and the Large Ratio Boost valve sonnax 4L80E-LB1. Dual feed provides more fluid to clamp the clutches used for 3rd gear. The large ratio boost valve provides higher maximum line pressure to clamp the clutches and bands tighter while still maintaining a reasonably low line pressure when cruising.
In addition, I'm doing these:
Actuator Feed Limit repair kit transgo 48-ACT-TL
Line to Lube Pressure Regulator Valve Sonnax 34200-14K
Torlon Check Balls (you need 8) sonnax 10000-08
No Walk Case Busing sonnax 34006-SP
replace rear case bushing with torrington bearing.
More clutches in the direct drum.
increasing the size of the feed holes for 1st, 2nd and 3rd.
remove and block the 3rd gear accumulator.
drill larger pump seal drain hole.
of course I'm replacing any worn bushings, seals and gaskets.
300M input Shaft.
Billet forward clutch hub.
I'm sure i'm forgetting some stuff.
I'm not going the transgo HD2 route for now.
I am not a 4L80E expert. If anyone is a 4l80E expert, I look forward to hearing your on topic remarks.
1st off the Torque Converter in a 4L80E is Real Heavy.
Weighs in close to 70 lbs.
Getting back to Rotating Mass.
Your going to need a High Dollar Triple Disc Lockup torque converter.
Expect to pay $2,000 + to start for it.
Be a smaller diameter & varies upon the ordered RPM stall or flash rpm rating.
A Pro Mod Smooth Sprag is often used.
Aluminum Drums are usually used at 1000 HP.
They do not last long on the street.
The steels cut into the soft aluminum.
Hard Anoidized helps but still the steels cut through it.
Titanium Drums are the real solution from COAN Racing.
The Overdrive unit is the weak spot also in a 4L80E.
Does not like having Huge HP through it at WOT.
Need full manual control of the transmission for sure at 1000 HP if your really going to drag race it.
That negates the entire auto shift of a 4L80E.
So in summary your better off with a Turbo 400 Trans.
Torque converter selection is Excellent & Very affordable.
Drag strip its 1-2 & 2-3 shift done only.
Never use 4th gear overdrive going down the 1320.
If you do it slows you down 1-2 seconds.
Some Use Borg Warner Tans.
Some use Alto Red Eagle frictions & Kolene steels like I do.
Some use Borg Warner HEG Greens.
Some Use Raybestos Red or Blues.
All up for Debate.
Dextron 6 ATF is not wanted for Drag Racing.
The Friction modifiers inside give granny smooth shifts.
All looks good on paper till Raceday.
Stuff is just too slick.
frictions & bands slip because of it from huge torque & Hp put into.
I use Castrol GTX Dex/Merc in my own.
Most use Hytran Tractor Hydraulic Fluid for Big power.
Others use Jet Engine Turbine Oil or special Air compressor oil.
Hytran Hyd. Fluid safest to use & no issues as a substitute for regular store bought ATF.
The Guys doing recipe builds never race.
Just happy to have you come back with your failed Auto trans.
Jakes Transbrake D1 & D3 gives full manual control to a 4L80E. Also Auto shift.
Again a Turbo 400 a better value for what your doing.
For $7500 put into a 4L80E a Turbo 400 does better at $2K built yourself.
No Overdrive. Let the engine sing RPM.
Not Pro Tour action.
Its Full Street Race & Drag race.
The Turbo 400 also has or had Asbestos lined Reveres Band .
Best ever made.