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just did a 4l80e swap on my turbo 5.3 car. shifts into od at 55..then lock up at 57. ...car use to cruise at 10% TPS now its 18+ and 12 vacuum... just to keep it at a steady cruise. 3.23 rear gears...prob are not helping . anyone else have this issue
That's weird. Especially a car with a turbo you would think it would take less throttle.
My gearing is much steeper and I have to fight it not to speed with 5% throttle in a 50mph zone.
Mine is programmed to lock at 47 and unlock at 30% throttle.
My first statement was wrong...i disconnected the lock up and it still take way more gas pedal to maintain speed. This is at 55. And one at 65. I was around 10% throttle cruising with the old setup
What was the old Trans? Any other changes like cam or tire size? What is the stall on the converter? If the previous trans was an auto what was the stall on it? Any other changes to the setup?
Last edited by LLLosingit; 10-21-2017 at 10:37 AM.
What was the old Trans? Any other changes like cam or tire size? What is the stall on the converter? If the previous trans was an auto what was the stall on it? Any other changes to the setup?
th350. 9.5" 3000 stall. 3" driveshaft.....no other changes besides 4l80e 10" 3000 stall and 3.5" driveshaft now.
I think "maybe" have to step up rear ratio OR check for TCC slip in 4th.
I went from a 350 also ...but doesn't feel any different in the 1st 3 gears as the are .004 less then the 350.
OD and lock up is awesome as I didn't have it before and can run rt 80 at 80 now if I want instead of being in the slow lane.
th350. 9.5" 3000 stall. 3" driveshaft.....no other changes besides 4l80e 10" 3000 stall and 3.5" driveshaft now.
There is your answer right there, Huge difference between OD and Non OD cruise rpm/load. When overdrive is used you are putting more load on the engine at a lower rpm = more throttle pedal needed.
There is your answer right there, Huge difference between OD and Non OD cruise rpm/load. When overdrive is used you are putting more load on the engine at a lower rpm = more throttle pedal needed.
right....so more throttle...less rpm still means less mpg...i think if i gear it up a ratio...get it back to its sweet spot..the rpms will be higher but less throttle..i hope
right....so more throttle...less rpm still means less mpg
Not necessarily, A lot depends the camshaft, Some just aren't efficient at low rpm and some work fine.
You can't go just by Throttle position and vacuum, Keep in mind that you are now traveling further for with every crankshaft revolution than you were with the none OD transmission. Changing gear will bring the rpms/vacuum back up but your still traveling a shorter distance.
In the end your still pushing nearly the same weight with the same engine although you should see a slight increase in economy with OD.
As I and LLLosngit said it's just a more inefficient rpm for the motor. I don't believe putting a higher gear in is the answer for you either. Being turbo I'm sure you really like the way them longer gears pull once boost really starts kicking in. Your probly better off just taking advantage off the lock up in 3rd while at 65 and under and only using od when cruising 70 or above.
As I and LLLosngit said it's just a more inefficient rpm for the motor. I don't believe putting a higher gear in is the answer for you either. Being turbo I'm sure you really like the way them longer gears pull once boost really starts kicking in. Your probly better off just taking advantage off the lock up in 3rd while at 65 and under and only using od when cruising 70 or above.
very true ...im sure at 70..75 it would be fine. Its just at the lower end of peak at 65
The way to compare economy is by comparing injector duty and engine vacuum. You can sometimes neglect the engine vacuum but it helps to factor in for accuracy because vacuum changes the injector flow rate (yes even in non-referenced setups).
The more throttle position typically means fuller cylinder- which means higher injector pulse widths. However the lower RPM means that overall duty cycle could/should be lower, which is what really matters most.
10-20-2017, 06:09 PM
5.3 W/4l80e swap....higher cruise TPS% 
