how big a difference are we talking about in rpms between a 2.73 and a 3.23 at that low of a speed?

 

i'm probably wrong, then. i just know my OD doesn't lock until 45 mph, but i never really cared to check when it actually shifts into 4th. i guess i never tried on my car.
honestly, i don't know. it's not really a question of RPM's, though. it's a question of shift points. i could guess, but i don't want to throw information out there i haven't verified.

 

So in summary, you'd recommend:

- PCM controlled/automatic 4-2 downshift from a higher speed WOT roll when already in OD.

and

- Manual 4-3 downshift (under no load), then PCM controlled/automatic 3-1 downshift at WOT for lower speed rolls where the trans will want to hit 1st gear.

Is that correct?

 

This is why I think the 4-1 will be seen more often in a 2.73 car, because of the shift points. I think that both the 3.23 and 2.73 car will hit OD right near 30mph under very light throttle, but the 3.23 car will only go back to 1st up to ~30mph, vs ~36mph for the 2.73 car.

 

i just dont see how you could run 4th at that low of a speed, i could be wrong....hell though in 4th at speed your doing only 2k rpms at like what 70-80 something with 2.73s...guess i just dont get the concept

 

so your saying a 2.73 car will shift into 4th around 36?

 

i'll try and find out tomorrow when i'm driving what rpm it shifts into OD not locked up under light throttle. i'll shoot for the lowest mph.

hopefully i'll remember to do this.

 

yea see id go do it....but i kinda currently dont HAVE a tranny in my car right now....

 

You guys are starting to go against everything i've learned about this subject...let me post what was advised to me:

But the question still remains though, the car is set up so that the average user wouldn't even think twice about this. He would nail it from overdrive, being an automatic that you normally don't mess with yourself. GM surely must have accounted for this in their design, you would think, but I could be wrong. I just don't see why they would design it so that 4-2 would burn up the transmission if thats how its driven by default, but that's what seems to be the general consensus among transmission builders on here.

 

As everyone has been saying, a 4-1 downshift is rare if it happens at all and so I honestly think it's a non-issue.
Here we have a dispute about the actual facts of what happens during a 4-2 downshift. Vince knows his stuff and says the band has to release, instead of it being a single event of disengaging the 3-4 clutches. But why would the band have to release for 3rd if it is a direct 4-2 shift? In any case, if we can ascertain which is definitely true here, we can consider this settled.

 

I can tell you for sure that it happens. My 2.73 car is already into OD at very light throttle by 35mph. But I can still get a downshift to 1st at 35mph, and it's actually quite a lot of fun. I can verify this on a-tap by watching "current gear" or whatever that field is called. I've been in 4th and seen it go to 1st.

So I'd still like to know if the 4-1 is better, or the manual 4-3 + auto 3-1.

 

Same here. I only put it into OD on the highway. Never around town. That's just way too much lugging on the motor for me to be comfortable with. Even more so with 2.73's. IMO anyway. 70mph is 2000-2100rpm's in my car.

 

as promised, i watched when my car shifts into OD not locked up.

my car shifts into 4th gear at 35-36 mph. mind you, i have 2.73's. this means i was mistaken. even in a 2.73 car, a 4-1 kickdown is possible. you're at ~1100 - 1200 rpm's.

 

Loading the motor is better than a high-rev/low load. I think GM proved that in their oil-useage TSB.

 

So once again I ask, can we get a final answer from the pros on what's the best WOT downshifting pattern to follow?

Manual 4-3 at no load, then auto 3-2 at WOT? Or just auto 4-2 at WOT?

- AND -

Manual 4-3 at no load, then auto 3-1 at WOT? Or just auto 4-1 at WOT?

It'd be great if we could solve this once and for all, because I'm tired of constantly doubting myself, as I'm sure others are as well.

 

That is going to depend how fast you are going. If you are doing highway speeds it is going to go 3-2. If you are going slower it will be 3-1 (which is my personal favorite). However pulling it back to 3 to get it out of overdrive, with foot still on the gas at cruise speed, was the way to go I was told.

 

Just curious, who was it that advised you to do this? FLT ( I noticed you have their trans)? If so their word means a lot to me.

 

I checked today with a couple of tranny builders that I know locally. Both unequivocally affirmed that on a direct 4-2 downshift, the band remains applied and it is just a matter of releasing the 3-4 clutch pack. Thus it is a simpler operation than the 3-2 downshift which must both release the 3-4 clutches and apply the band. So regarding your first question, it seems the simple 4-2 downshift is best. When it comes to the >1 downshift, as I said, I lean toward the manual 3 to automatic 1 because in that case, the 3-4 clutch pack simply disengages. 4-1 must disengage the clutch pack and release the band. But overall, I just don't think that the difference between any of these options is a matter of life and death to your tranny.
Anyway, that's my story and I'm stickin' to it.

 

but that's entirely contrary to what vince said. vince said it takes more work to do a 4-2 downshift and more stuff gets released.

i honestly don't think anyone knows 100% what happens inside the tranny when you're moving and exactly how detrimental these things are. all i can say is, if your tranny blows because of a WOT downshift, it was gonna blow anyway. transmissions just don't blow on stocklike rides - it's a long time coming. as for highly modded cars, your 4L60E will have to be beefed up enough to hold the power anyway so if it's built right, it really shouldn't matter as your bands/clutches will be beefed up. if you're running a stock 4L60E in a highly modded car and it blows, it deserves to anyway

if you're gonna race the car nonstop, something will eventually go. you may as well go out there and have fun. for me, i'll stick with the manual downshift to 3. even if it's harsher for that 1 second of downshift, it's definitely easier on the transmission for that WOT pull.

 

Just give it up and get an M6.