4l80E Trans/Rev and Speedo Calculations?

[cthulu]

Hello, I swapped an 05 burb drivetrain into my project truck and it has the 4l80E. I updated the gearing and tire size and auto sized tables but speedo is way off (50% of actual speed) and shifting isn't happening under wot in certain conditions.

I'm trying to find the formula to calculate trans rev/mile and the Pulse per mile, if anyone has them handy it would be greatly appreciated.

Trans is the 4L80E, should be a 40 spline shaft, 315/35/20's and 3.42 gears, mostly looking for the formular so I can sanity check some tables.

[TheMechanic]

It is the gear and tire wizard. Post your tune with your tire size in inches MEASURED with a tape measure. Not the size on the tires and your differential gearing and I'll help you out.

[2xLS1]

Gen 3s are the easiest to set gear ratio and tire size calibration. I don't see any way you could get one 50% off. What does the scanner show for MPH and is the 50% error in the scanner or cluster. Since it appears to be a swap what is the cluster you are using? Also on Gen 3s you need to subtract .8" from what a tire size calculator shows for the tire height you are using. But even not doing that it would not be 50% off.

[cthulu]

It is the gear and tire wizard. Post your tune with your tire size in inches MEASURED with a tape measure. Not the size on the tires and your differential gearing and I'll help you out.

Not sure what you mean by tire size with a tape measure, if you meant literally then they are around 28 5/8 to 28 3/4 (have 28.7 in the tune now)

[cthulu]

Gen 3s are the easiest to set gear ratio and tire size calibration. I don't see any way you could get one 50% off. What does the scanner show for MPH and is the 50% error in the scanner or cluster. Since it appears to be a swap what is the cluster you are using? Also on Gen 3s you need to subtract .8" from what a tire size calculator shows for the tire height you are using. But even not doing that it would not be 50% off.

Tune attached, I'd really just like the formula though as I initially used the gear and tire wizard. Using the stock cluster from the burb and moved over the entire harness so the stock column and everything else works.20231103_Backup342Gears.hpt

[TheMechanic]

https://getallcalculator.com/vehicle...pm-calculator/

Pulse per mile (PPM) == ((63360/π.diameter of wheel) x Gear Axle ratio) x no. of gear teeth.

that lower case looking "n" before the .diameter is the pi symbol

[cthulu]

https://getallcalculator.com/vehicle...pm-calculator/

Pulse per mile (PPM) == ((63360/π.diameter of wheel) x Gear Axle ratio) x no. of gear teeth.

that lower case looking "n" before the .diameter is the pi symbol

That gets me the PPM, won't I also needs trans rev? From what I have read the PPM gets your MPH in but there is another setting for trans rev right?

[TheMechanic]

You don't need trans revs because it is already known in the ECM/PCM/TCM. It will be its output speed sensor.
They key to getting other speedometers to work is in the "PCM Output Calibration"

[cthulu]

You don't need trans revs because it is already known in the ECM/PCM/TCM. It will be its output speed sensor.
They key to getting other speedometers to work is in the "PCM Output Calibration"

Well, here is a twist. The PPM is spot on.

Now, I am sending the 4wd 4L80E into a borg warner 4472 (typoon/syclone transfer case) But, this doesn't change gearing at all. One rotation = one rotation out the other side, it is an awd tcase.

F me.png


This is why I wanted to formula for trans rev, to make sure it's right. The PPM is spot on using the manual calcs but I don't know the formula for trans rev

[cthulu]

Well, here is a twist. The PPM is spot on.

Now, I am sending the 4wd 4L80E into a borg warner 4472 (typoon/syclone transfer case) But, this doesn't change gearing at all. One rotation = one rotation out the other side, it is an awd tcase.

F me.png


This is why I wanted to formula for trans rev, to make sure it's right. The PPM is spot on using the manual calcs but I don't know the formula for trans rev

So the formula should be (63360/Tire Diameter*pi)*gear Ratio my formula would be (63360/28.7*pi)*3.42=2,403.3084 so I was off by 200, I updated it...and the speedo and shifts are still off.

This has to be something simple I'm missing!

[RDF1]

First thing i would do is take the VSS out of the transmission and look in there to see if there is a Reluctor wheel.
IF it is missing, the VSS is picking up the park pawl teeth on the output drum.
The speedo will be about 50% off as well if this is the case.

This means your gonna need to pull the trans and take it all the way apart to put in a $20 reluctor.



If it looks like this... you need the reluctor..


Here is another picture so you can see what the 2wd reluctor looks like.

[cthulu]

Crap, I did have it rebuilt by a budget trans shop. Would suck to have to do this, thanks for the tip i'll poke around and see if I can view with truck cab on or if i'll have to pull it.

[RDF1]

Pull the sensor and use your phone to look in there.

[TransGo Robert]

First thing i would do is take the VSS out of the transmission and look in there to see if there is a Reluctor wheel.

Pretty sure you nailed it, it is usually something that happens when someone put a 4WD into a 2WD application and only swap the output shaft. 4X4's normally use the sensor on the transfer case not the OSS on the transmsision so no reluctor on the planet.

[cthulu]

First thing i would do is take the VSS out of the transmission and look in there to see if there is a Reluctor wheel.
IF it is missing, the VSS is picking up the park pawl teeth on the output drum.
The speedo will be about 50% off as well if this is the case.

This means your gonna need to pull the trans and take it all the way apart to put in a $20 reluctor.



If it looks like this... you need the reluctor..


Here is another picture so you can see what the 2wd reluctor looks like.

F**k, they missed the reluctor wheel didn't they.

signal-2023-11-11-114048_002.jpg

[cthulu]

Well, update for everyone reluctor wheel is not there. Which is weird as during the rebuild they would have had to press it off.

The good news is the vss from the 4l80 and the borg warner 4472 vss senaor both ohm out around .140 and the birg warner senaor also has 40 teeth and is a 2 pin sine wave. Testing it next week.

[TransGo Robert]

Well, update for everyone reluctor wheel is not there. Which is weird as during the rebuild they would have had to press it off.

They didn't remove it, it is simply not there on 4X4 applications.

[cthulu]

That doesn't make any sense as there is a vss sensor right over where the ring would be. This trans is from an 05 4x4 2500 suburban.

Further on a long roadtrip I was having shifting issues as that specific sensor had failed. Replaced the sensor and all bueno. When I pulled the drivetrain out of the burb I had the shop rebuild it before install.

Getting the truck running now speedo is off by 50%, seems like its picking up the parking brake pawl as the ring right behind the vss is missing.

[Lsyjbrad]

im currently having kind of the same problem.. trying to figure out shift points and getting the speedo dialed in... when i got the transmission rebuilt i got him to put in a reluctor wheel, 40 tooth count i belive.. now its reading from the vss sensor, but after i use the gear and tire wizzard the speed in the scanner is waaay off.. isnt it meant to correct it? lol could there be other values im missing?

[cthulu]

Use the formulas in this thread to double check the math, update us with reaults.

Speaking of updates! Using the borg warner 4472 40 tooth reluctor and atock senaor from the 91 bravada worked great with my 05 burb drivetrain. Speedo now reading accurately.

The trans is upshifting early still and bogging on wot, Same as before but I think its an issue with the internal harness or wiring and not the tune.