Efficiency range is 1800-2000 rpm, as far as I know. Anything under that and you are lugging it. What are your RPMs at 45mph?

 

ok, but I m running lite, not hauling. Plus the land here is mostly flat

 

Next time I go for a drive, I will write it down, the rpm drop as it shifts at 50mph.
I am stock everything, gears are that 3.73 standard gears.
RPM makes a pretty good drop when it shifts.

 

Manually downshifting?

 

Custom Tuning, should be able to change ECM/TCM curves for 48re shift points

 

Rob's tuning can lower the lockup to wherever you want it. Otherwise, mystery switch.

 

What is this 'mystery switch'?

Has anyone tried lowering it and did it change the mpg?
When the truck at 50 switches gears, it is definitely not lugging.
I can taper back the throttle, and it does fine.

 

It's a manual switch to make the TCC lock up on command - manually actuated. Look up the term "mystery switch" and you'll find it. Not hard. Just need a switch and some resistors. The ECM throws a ground to the TCC solenoid to make it lock up. This switch just kicks it to ground but needs a resistor so computer doesn't think there's a prob.

 

Locking at 45 mph or 50 mph will not change your mpg unless you insist on running unlocked. 45 locked and 50 locked will be the same mpg - or close enough to be negligible

 

My 95 will stay locked up in third if I shut the od off, there is that mph spot on my truck at 45-47mph where it will shuttle between 3 and od, so around town I turn od off... cruising with a empty truck at 1500 on flat ground won't hurt a 12v, trying to pull a grade with a load on at 1500 is a different story...

 

As I slowly accelerate, exactly at 50mph the RPMS drop from 1800 to 1400
If I keep going to 55, the rpms are at 1500
It holds the lock till I drop back to 47, not exactly sure, hard to be certain.

At 50 with it locked, rpm at 1400, if I press the tow-haul button, rpm jumps up to 1800, toggle it again, rpm drops to 1400.

The truck pulls very well at 50 with 1400 rpm.

TCC lock on, whole idea is better mpg due to no slippage.

 

TCC lock on, whole idea is better mpg due to no slippage.

Let it lock at 50-52 and then set the cruise on 50 is simplest for best mpg on flat ground with no load. If you want full control of it, then do the mystery switch.

 

Also you could get yourself an Anteater tranny controller. That way you can program the 48RE the way you want it, even the old ones without a TV motor. Actually I am thinking of trying this myself since I hate the loose feel of a disengaged TCC below 50mph. IT would certainly wake up the rig if TCC is engaged already in 2nd or 3rd gear.