Power adders, gear ratio, and tc lockup

[DA BIG ONE]

After reading some interesting info on this site I'm guessing I really blew it when I went to 3.42 gearsets, 33" tires & adding mods to increase HP/TQ effectively moving my peak TQ up to 2,200 rpm's.

To be at 2.200 rpm's at say 70 mph I need to stay in 3rd gear but not really sure if tq/converter locks in 3rd gear driving in such manner. Any of you know if it does I'd like to hear from you.

Is there a way I can monitor real time fuel data at speed?

[More Power]

You can move the torque peak up or down by simply moving the boost pressure peak rpm. With these pickup diesel engines, 1800 rpm is a magic number, no matter whether you're running a non-turbo diesel or a turbodiesel. This rather special 1800 rpm number is also there with the Jeep CRD and other diesels beside the GM 6.2/6.5/6.6. I think this has a lot to do with a combination of diesel engine thermodynamics, mechanical considerations and vehicle speed that produce the 1800 rpm general rule.

You could run your own tests, using both OD and 3rd gear, but I'd bet you'll see the best fuel economy somewhere nearer to 1800. :)

Jim

[DA BIG ONE]

Jim does the 4L80 tc lock in 3rd, or?

[Robyn]

The TCC will lock in 3rd.
All the rigs I have owned with a 4L80E will lock up in 3rd
Just put the rig in 3rd and start off a watch the tach and count your shifts.
You will get the 1-2 the 2-3 and then in a little bit you will see the tach drop slightly as the TCC engages. and to prove it hold your speed steady and lightly tough the brake enough to activate the brake switch and you will see the RPM's rise slightly as the TCC unlocks.
If im pulling a long hill and get slowed down a tad and dont want to mash the thing harder to bring about a 4-3 downshift I will slip the left foot over and touch the brake and drop out the TCC and that is just enough with the converter back on line to increase power and the speed will climb. I then just get off the pedal and let the TCC come back on.
Robyn

[rjwest]

The TCC will lock it 3rd gear at the same speed it will lock in O/D, But, if to much throttle is required to maintain speed
the TCC will NOT lock or will unlock as soon as throttle/load is
applied,

Note, also the tcc will unlock when releasing throttle,
so you may have created a very small window where
TCC is locking....

You can force the TCC to stay in Lock up with the resister
trick, TCC will stay locked untill down shift, than lock up
in 2nd, ( but very harsh shifts occur ).

[DA BIG ONE]

Throttle response is always good on my burb, but, It has been suggested that I drive it in 3rd on highway to keep it @ 2,200 rpms to see if mpgs go up.

These figures were given to me by Heath for my motor: 320HP @ 3,500rpm's, 550 ft lbs tq @ 2,200rpm's

Other things do play a part herein but thinking of trying this 2,200rpm test a bit to see if anything does change as far as mpg.

[rjwest]

My experience: with the TCC locked, the higher gear is most
always the lower fuel rate for a given speed ( scan tool ).

Except, under load at low rpm where 3rd , TCC locked )
has a lower fuel rate, but not by much...

Note: this is on a stock PCM .