Awhile back I had read somewhere that the "smooth" transmission shifts which the Expedition is noted for actually use more fuel due to the allowable slippage between gears so that the shifts are less noticeable. And, if the shifts were shorter there is less "waste" of energy between shift points and ergo, better fuel efficiency.

Wondering if anyone could clarify or add to that idea? Has anyone done the J-mod and found better efficiency?

After filling up this am at 3.37/gal, and being told it was going up again later this am I am really trying to squeeze what I can out of my 03 4.6.

Any information about fuel efficiency w/ shift points and the J-mod is appreciated.

 

The "j-mod" is NOT recommended for trucks.

Steve

 

I've read about valve bodies that you can buy, and the j-mod is all over the net . What exactly is everyone doing that changes the shift pressures (quicker) that suposedly wastes less fuel?

 

*IF* it makes a difference at all, and I doubt it, it's going to be such a small improvement that you wouldn't be able to measure it.

 

I also own a 1998 Lincoln MarkVIII, which is one of the vehicles with a huge "mush" zone between gears. Ford figured people spending $45.k on a luxury sport coupe did not want a firm shirt. It feels like crap with so much shift delay. Other people I met thru a Mark forum at a meet did the J-mod and their shifts are quick and crisp. They are all happy who have done it.
In short what the J-mod does is by drilling several of the very small holes in the seperator plate slightly larger, allows faster fluid flow out of gears which have been passed instead of holding them longer.
I have done many shift kits in the past on AOD's which instructed you to do the same hole drilling, plus gave you upgrade parts to firm up other areas of the trans, either for HD truck use, street ,or strip performance.

I personally will be using a shift kit soon, in both my car and trucks 4r70w.
I figure, if I'm going to go thru the work of dropping the valve body, everything is going into it.
As for fuel economy? I dont know, but I would guess it could be a plus?

Lowflyingbird

 

A Mark VIII is not a truck.

 

First off I see you have a 4.2 with a stick. You should be more worried about your head gaskets than a J-mod.
Now back to transmissions.
OK, MarkViii =3600lbs. with a 4r70w, F150 4.6 ext cab= 4400lbs. with a 4r70w. 800lb difference. MarkVIII either 308 or 327 gears, F150 355or 373 gears (common). I think that transmission < vehicle weight and gear difference equal out quite well.

Rediculous comments aside, The two vehicles share the EXACT same transmission, a 4R70W weather it be a two or four wheel version. I stand behind what I previously stated as a mechanic. A firm transmission is best, Ford only overlapped gears to make the ride feel smoother. Any good transmission tech will agree, In these heavy vehicles a firm an perceice shift is best. It will also make your transmission stonger and last longer.

As I mentined in posts before, I'm installing a Lincoln Aviator 4.6 DOHC into my F150, I'm also using a low mile MarkVIII converter/flexplate on my trans. It's a 10 7/8 bolt converter approx 2k stall. This is to go with the Complete shift kit I mentioned.

Lowflyingbird

 

Stick your Mark VIII where the sun don't shine, assclown. Steve has EARNED my respect on these boards and when he says something, I listen.

 

Okay, so what is the Mark VIII?

 

Last I looked, it was a car.

 

It's a truck.

It's a car.

It's a truck.

It's a car.

Are we talking about the Chevrolet El Camino here?

 

Yea the Mark VIII is a car - My X worked on the launch - Somewhere around 93 @ the Wixom Plant. I don't think they lasted all that long 5 0r 6 years.

Anyway - Who said it was a truck, you foolish mortals ?? - Maybe it's one of those transformers ehh

Positive firm shifts is - more better = less friction, heat, slippage and in-turn better economy. Thats where a sticks can one up and automatic.

At least that's my understanding of things. I went from long drug shifts to firm ones. In this case - the trans seemed to heal itself overtime, but it had high miles and slipping pretty good before I worked on it.. It doesn't hit hard , but there is no pause what so ever between gears anymore.

I guess I'll call it the J-brew mod - since I fabbed the plate.

Different trans tho -E40D - So totally disregard this post.

 

there was the ranchero, coulda kept it in the f'n family and named a ford man! :P

OP never made notion that it was a truck, "other car"

who was badmouthing steve?

 

But there definitly are some issues there. Maybe it's that 4.2? Maybe it's V8 envy?
Maybe I hit a soft spot with the head gasket issues that those motors have. Not mentioning the bad crankshaft ,connecting rod and balancing issues.
OH NO, there I go again bad mouthing him.
Seriously have a

 

I shouldn't have slammed you like that and I apologize, but this is how it is:

The OP asked about a J-mod for his TRUCK. Steve said that J-mods were NOT recommended for trucks. You hopped in touting the J-mod in your CAR. I simply pointed out that your car was not a truck. For that, I get slammed, told that because I drive a V6 truck with a stick I should butt out. That's not how things work.

My head gaskets and everything else are fine, by the way.