hoot

What tells the 48RE when to shift?

j-fox

Ground speed/hydralics for 1-2 ans 2-3, then computer for 3-4 and converter clutch.

hoot

How does it know ground speed and how does it take that info put it into hydraulics?

dozer12216

Vehcile speed off rear axle ABS speed sensor.
Output shaft RPM off speed sensor on extension.
Temp from sensor in gov presure transducer.
Brake switch.
Throttle respense from Throttle cable. Your request for engine power on consequentlly, appropiate shift timing and quality.
Vable body tuning spring pressure vs gov pressure.

j-fox

Ok, it is too much info for me to explain it here. But, it does have a ground speed sensor, when the speed increases a valve gets pushed against a spring. When the spring compresses far enough the valve moves , signals the shift.
You need to buy a factory service manual, it explains it all.
There is a cable that is adjustable, it will change shift points.
What are you trying to do?

annabelle

Computer does not tell the tranny to go to 4th. Gov. pressure sensor and selinoid do. Pressure.

no_6_oh_no

No, OD is purely computer controlled. The only pressure related operation is it is locked out until trans is in drive.

Essentially, as speed goes up the ECU sets gov pressure higher and higher until it overrides the TV pressure, then shift happens.

hoot

I'm trying to figure out why my 48RE goes into a mode where all of the shift points shift back about 500rpm. It starts shifting waay too soon, lugging the motor and barking my turbo. Seems like it does it after it's hot.

I have been having some problems with my TST box (moisture) causing stalling and no-starts and was wondering if the TST can mess with shift points if something gets hosed.

I have the TST disconnected now with just the Smarty now. So far it's shifting perfectly.

BTW the first time it did this I didn't have the Smarty yet so that's not the issue.

Ram Daddy

I also have the TST and have issues with the shifting as well.....I haven`t tried taking it off , because I didn`t think it could be related....maybe it is?

Anyone know?

annabelle

Computer sends no siginal to shift to 4th.

S/P G671

my 48re does not have a cable to operate throttle pressure,it has a electric motor atached to the t.v. shaft potruding from the valve body and it is controlled by the apps and computer,these transmissions sometimes have a mind of thier own,if the puter senses that the trans is hot it can put the trans into lockup sooner to try and cut down on the heat produced by converter slippage,your t.v. actuator may be sticky or intermitently faulty,your apps may have a flat spot,or it could be just a sticky shift valve.try a service on the trans,if there is sediment on the bottom of the pan it could be a sign of a problem...Good luck.

hoot

I'm learning good stuff here. We'll see how it goes with the TST disconnected. If I get through some hot times an it doesn't get goofy I will pretty much suspect the TST. Other than that if it still does it I may need to invest in a trans temp gauge and a trans cooler. This is a new Goerend.

That's if it's not a harness or sensor issue. Is there a sensor that if it goes bad or acts goofy when hot can cause premature upshifting?

HOV

If that's the case, I have two questions:

How does the electronic switch to disable OD work?
Why is the 48RE called a 48RE? Why not a 48RH then?

DBLR

IIRC the E stands for electronic and I've forgotten what the other letter and numbers were for.

grantx5

4 - # of gears
8 - refers to torque but not sure why its an 8
R - Rear wheel
E - Electronic