How hard is a WOT 3-2 on the 4R70W?

[1997ThunderbirdLXV6]

How hard is the full (or almost full) throttle 3>2 shift on the transmission?

Just curious because it's a pretty common scenario (with the stock calibration).

Imagine a highway crossing, a tight ramp at around 35 mph. I'm in 3rd at this point because I turned O/D off during the ramp, in anticipation of speeding up.
Coming up to the straightaway, I push the accelerator, the TCC unlocks, which puts me to about 2,000 rpm - which simply isn't enough to accelerate at a decent rate.
So I push the accelerator down further...still nothing...further...and finally I get a 3>2 shift and the car speeds up.

That 3>2 shift requires either full throttle or at least 80% throttle, or something in between. Otherwise the car just stays stubbornly in 3rd.

Drivability is fine given that I know and anticipate this behavior.

But back to my lead-in question: is a full-throttle 3>2 shift harmful? Because there's literally no way to prompt this shift without such throttle input. I don't see myself pulling the shifter into 2nd to prompt the shift that way.

 

[Jae 'Bird]

How hard is the full (or almost full) throttle 3>2 shift on the transmission?

Just curious because it's a pretty common scenario (with the stock calibration).

Imagine a highway crossing, a tight ramp at around 35 mph. I'm in 3rd at this point because I turned O/D off during the ramp, in anticipation of speeding up.
Coming up to the straightaway, I push the accelerator, the TCC unlocks, which puts me to about 2,000 rpm - which simply isn't enough to accelerate at a decent rate.
So I push the accelerator down further...still nothing...further...and finally I get a 3>2 shift and the car speeds up.

That 3>2 shift requires either full throttle or at least 80% throttle, or something in between. Otherwise the car just stays stubbornly in 3rd.

Drivability is fine given that I know and anticipate this behavior.

But back to my lead-in question: is a full-throttle 3>2 shift harmful? Because there's literally no way to prompt this shift without such throttle input. I don't see myself pulling the shifter into 2nd to prompt the shift that way.

I know we have different trannies (mines the aod yours is the 4r70w) but mine does that too, its stays in 3rd until almost FT then it kicks down and actually has power lol (3.8 life amiright?) I dont think it causes harm but I try not to do it all the time. that's my 2¢ anyway, someone with more experience can probably help more but hey sample size of 2 doing it is not bad and probably means its more normal than not.

 

[Grog6]

4-2 is the bad one. 2-3 wot can spin a one-way clutch.

 

[1997ThunderbirdLXV6]

3.8 life amiright?

Yup!

 

[1997ThunderbirdLXV6]

4-2 is the bad one.

4 to 2? Wouldn't there be 3 in the middle? Think automatic shifting. No touching the shifter.

In my driving, full throttle in 4th just doesn't happen. Either I ease into the throttle, and it automatically shifts 4>3 well before I reach WOT, or I already turned off O/D if I accelerate hard.

2-3 wot can spin a one-way clutch.

Wait, you're talking  upshift now?
What speed would a WOT 2>3 shift put me at?
I don't think I hold WOT that long. I just accelerate to maybe 50 mph, then gradually release the throttle, and it shifts to 3rd.
I'm guessing a WOT 2>3 shift would be over 70 mph (?).


I'm just concerned about the WOT 3>2  downshift.

 

[Grog6]

If you never touch the shifter,and drive mellow, the biggest issue you'll run into is the stock tunes' shifting to 3rd with minimum throttle in traffic. The constant 3-4, 4-3 adds heat to the trans, and degrades the fluid. Adding a trans cooler helps that. I wouldn't worry about the 3-2. If you plan to keep your car forever, and you explore jy stuff regularly, find an 02 trans from a non police gran marquis or crown vic with low miles, and buy that, with the tc. (they usually come together. I can guide you on a rebuild kit; then take your time rebuilding it. Properly rebuilt, j-modded, it will outlast you.
Seal installers are $30 on amazon, a rebuild kit is ~$300, trans ~200,special parts ~100. Hardest thing rebuilding one is cleanness. Your trans is 28 years old; it will eventually start leaking pressure off the direct clutch from hardened seals, making it slip, and it will lose all the friction material. When you first feel it slip, get home,lol. Hopefully it will be years.

 

[theterminator93]

find an 02 trans from a non police gran marquis or crown vic with low miles

This doesn't apply to him in this situation, as he has a 3.8... and no Panther came with the later 4R70W and SBF bellhousing. His best bet is a trans from a later New Edge SN95 with the V6, or possibly one of the late second-gen 5.0 Explorers.

The 3-4/4-3 is certainly clunky, but it's the 3-2 that stresses the one-way clutch. The problem with a 4-2 is that while yes, the PCM is technically commanding 3rd for a brief time, but under high TP and RPM the trans physically can't do everything required to get out of 4th fast enough to fully disengage 4th before the 3-2 kickdown starts, and there's a lot of stress on the one-way clutch as it suddenly goes from overruning at a high RPM with a lot of rotating mass and torque behind it to hold... to locked. This is why repeated high TP 3-2s (and especially 4-2s) have been known to kill the one-way clutch. That part was replaced with the much more robust mechanical diode starting with the 98 model year.

 

[1997ThunderbirdLXV6]

This is why repeated high TP 3-2s (and especially 4-2s) have been known to kill the one-way clutch.

Well, I'm not worried about 4>2 because that scenario (full throttle in 4th) just isn't something I do.
Either I ease into the throttle, giving it plenty of time to complete 4>3 before I reach a throttle position that would then prompt 3>2; or I've already turned O/D off.

Full throttle in 3rd  is something I do though.

So would it be healthier, instead of prompting the 3>2 shift through full throttle input, to pull the shifter into 2nd while at part throttle, wait a second for the shift to complete, then floor it?
Sounds jerky to me due to temporary engine braking, but not sure how it would feel in practice.

 

[theterminator93]

TBH, with the N/A 3.8 the grenaded roller clutch is nowhere near as likely for you because 1) the engine obviously makes less torque than the 4.6 and SC, 2) you have a 97 which has some improvements to the valve body already (though a J-mod will still help quite a bit) and 3) the car is also lighter with less mass to act as a battering ram against the transmission internals during driveline RPM changes.

I wouldn't try going to into manual 2 for hard acceleration for a few reasons. First off, it takes as long to properly engage as going from 3rd into OD because the OD band has to apply - not the greatest scenario when you need to get moving quickly. Second, manual 2 was designed with engine braking in mind; the OD band will hold but it isn't a good idea to subject it to WOT pulls either. In factory trims the 4R70W never goes/stays in 4th gear with the OD band applied during WOT runs. Third, it's one more thing for you to have to think about/distract you when you're probably already in a situation that requires you to focus on sequencing yourself into moving traffic... and if you forget to switch from manual 2 into D while accelerating you could hit the rev limiter, etc.

Trying to avoid WOT 3-2s entirely would be impossible, but if you're already in 3rd and are accelerating into/anticipating a 3-2 downshift, applying the throttle just enough to get it to kick down before going WOT (most of the time) would be more than enough to baby the trans along.

 

[1997ThunderbirdLXV6]

Thanks, @theterminator93

That's good because I like to keep my hands on the wheel.

But it brings me to another question. I've read many times that 2nd while in D isn't the same as manual 2nd because manual 2nd utilizes the O/D band for engine braking. How? I mean what does one have to do with the other?
And is this a mechanical distinction, or an electronic control? In other words, could a tune provide a manual 2nd which does not utilize the O/D band?


Generally speaking, my approach is: I'm driving an automatic, so let it do its thing.
That said, I do use manual 2nd regularly in parking lots because otherwise it constantly shifts 1<>2. But I shift into manual 2nd at barely rolling speed, so there is no discernable engine braking.
And as I said previously, I use O/D off all the time. Mostly I turn O/D off while still in 3rd to prevent an unwanted upshift when I anticipate, e.g., a stop light, a downgrade followed by an incline, acceleration, etc. Occasionally, I turn O/D off while in 4th, e.g., heading uphill, or coasting down to mid-30 mph like in that highway ramp scenario above.
Ever since I moved the switch to the steering column, it's become second nature to use it. With O/D on/default, the car seems to lug the engine before shifting, even if only briefly, and that lugging feeling is very unpleasant.


Meanwhile, this conversation inspired me to look at my transmission fluid which is a bit over 21,000 miles old (full drain and refill). I siphoned out half a cup. This is what it looks like: somewhat opaque, but still red, no larger floating matter, and the smell is identical to fresh fluid, though somewhat less smelly.

 

[theterminator93]

Here's Jerry's description from the thesis:

There are a few other cases worth talking about. If you recall, a one-way clutch holds in one direction and spins in the other direction. The locking feature of a one-way clutch only works if the input speed is greater than the output speed, or, or are power on (into the throttle). In overdrive or drive range, the low one way clutch holds in 1st gear as long as you are power on. If you were to go closed throttle, and stay in 1st gear, the engine will return to idle. To allow for coast braking in manual low, the reverse band applies which locks the planetary carrier to the case just like the one-way clutch in overdrive or drive range. In manual 2nd, the OD band applies to lock the reverse sun gear and allow coast braking.

The above explanation on the function of the transmission is pretty technical. Here is a very quick summary.

1st Gear, the forward clutch is applied​

2nd Gear, the intermediate clutch applies​

3rd Gear, the direct clutch applies​

4th Gear, the OD band applies AND the forward clutch releases​

Manual 1st Gear, forward clutch and reverse band apply​

Manual 2nd Gear, OD band applies​

​

Manual 2 is a hydraulic change in the transmission; it is not an electronically commanded gear. The position of the manual lever changes the fluid flow to engage the necessary clutches and servos to provide the desired gear. In "D" the control of each of the gears is achieved by the PCM operating the shift solenoids controlling the valves which direct clutch/servo fluid flow.

Using manual 2 as you've described is fine. Aside from engine braking, it's also useful for reducing wheel torque when driving at low speeds, e.g. on snowy or icy roads.

 

[Grog6]

I have spun the one way, against it's will, which is why my goto is a later trans. I just always forget about 6 cylinders. lol
I was thinking upshift, but I remember now, it being a 3-2 at wot, passing a slow driver. It makes an unforgettable noise.
Dude will never break one, most likely.

Thanks, brandon! iavo, lol.