I was talking to a guy that remarked that when the drop-4-cylinders on shifts is eliminated via a chip can be pretty hard on the trans. Eventhough our transmissions are heavy duty from the get go, this feature on the stock PCM is to preserve the trans. I've also heard that an automatic trans that shifts firmer as apposed to softer is actually better for a trans. The softer shifting trans creates more heat and is set that way only for comfort and smoother overall performance. Is there a knowledgeable trans technician that can speak to this.

Thanks

 

Not a trans expert, but I pay attention to them . Pretty much exactly what you said. The slushy comfort shift of the stock program creates slippage and excess heat. Both trans enemies.

------------------
Red '00 Lightning,
Adopted 4/19/00,
Power Surge Performance enhanced,
Sound effects provided by Flowmaster,
Track time pending...

 

So then the ideal transmission settings would be neck snaping shifts with 4 cylinders only to avoid over stressing the parts ??

 

I would consider myself a transmission expert (I've built about 4 Million 4R100/E4ODs), and yes, the softer the shift, the more heat, and heat is the enemy, I've never heard of the 4Cyl shutdown being for the good of the transmission, I thought it was for the cams/lifters valvetrain in general....I'd be more than a little surprised if the Transmission was the weak link..in fact, it's not, can't be...
(thinking and typing a the same time),,max torque is 440 ft/lbs, period it never gets over that no matter what you do....convertor multiplies flywheel torque x2, so max on the input shaft is 880 ft/lbs of torque, and the transmission is rated for 1000 ft/lbs of torque, soooooo, nope, can't be for the tranny, the 7.3 deisel actually puts more stress on the transmission than the Lightning 5.4 does.
A transmission really doesn't care about horsepower, it's only directly affected by torque, and all the specs in a tranny are designed around maximum torque. It doesn't matter how quickly the torque is applied, if the box is rated for 1,000 ft/lbs, you don't need to "gear down" a 440 ft/lb engine to save the tranny...


Now, i've got that figured out...

G

[This message has been edited by Factory_Tech (edited 06-08-2000).]

 

Ok If the Trans can handle the power or all 8 cylinders why cut out 4 ? For Driver comfort ?

Doug

 

Factory_Tech

Wow, I don't think I could've gotten a better person to answer my question. I wonder what the real answer is on why they use only four cylinders on shifts. This is only used for WOT shifting isn't it?

 

I'll agree that the firmer shifts may be inclined to prolong tranny life, but not u-joint and rear-end life. There is always a bit of lash in any system of shafts, joints, & gears behind the tranny, and repeatedly taking up this lash by violent means must -decrease- the lifespan of these parts.

Fortunately it is easier and cheaper to service u-joints & rears than trannies so this may not be so much of an issue to the performance minded person. It is worth remembering though than an unconstrained driveshaft (resulting from a broken u-joint, for instance,) can cause serious damage to the truck and is a major safety problem if no driveshaft loop is present.

-tvw


[This message has been edited by tvw (edited 06-08-2000).]

 

One of the first things I'm adding to my new L is a trans temp gauge. Is anyone else running one with a stock cooler?...Does it perform well in traffic, at strip, etc.

 

I believe Silver_2000 is correct. The soft shifts are for driver/purchaser comfort.

 

Im confused again. This quote

Another point I wanted to make is that the shift firmness in Position 2 of the CUX1TRAC program is going to be noticebly softer than in Position 1, due to the torque converter being maintained at maximum stall to increase acceleration in Position 2. Just like when you install a loose, high-stall speed TQ, the same thing happens.

Shifts going to be softer for HIGH performance ? (position 2)

Help !

 

Ok...then Factory_Tech....

Is the increasing of line pressure in the trans not a bad thing? Doesn't doing that create more damage on the seals/servos, etc.?

Just curious.

Paul G.

 

PB Gas,
Line pressure actually inside the transmission isn't really an issue, the internal seals are over engineered, and we're still talking aobut a box rated for 1,000 lbs, bolted to an engne rated for 444(880), but the lash factor on the downstream drivetrain is a pretty serious issue, and maybe that's the weak link. The rearend is pretty stout, and it comes with the "big" driveshaft, but like someone said, even new there's some lash, and every time you drive it it gets a little looser.
Hmmm, lemme think about this some more, maybe ask around at work.

G

 

All lash(another name for slop?) would be taken up when at WOT. Correct?

------------------
Red '00 Lightning,
Adopted 4/19/00,
Power Surge Performance enhanced,
Sound effects provided by Flowmaster,
Track time pending...

 

Yes, lash would be taken up at any load, not jsut WOT, but the issue is how hard you "jerk" it.

 

Been reading this post, don't have a chip but here goes...

I noticed there is another thread titled chip & filter = +70 hp and +98 ft/lbs of torque! (along those lines). That would mean about 538 ft lbs of torque at the flywhee somewhere, which equals 1076 ft/lbs. That would exceed your factory built margin of safety.

Factory Tech, would you get a chip that does this? Sounds like I want a chip that makes the shifts firmer, takes care of the richness (problem?), but keeps the same red line. Don't forget about the drop 4 cylinders, get rid of that, too.

On another side note, where does horspower fall into this? Its gotta be apart of the equation.