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Who can't leave the O/D button alone?

  • always pushing button

    Votes: 41 48.2%
  • rarely push button

    Votes: 21 24.7%
  • only turn on O/D on highway

    Votes: 14 16.5%
  • what button?

    Votes: 9 10.6%

  • Total voters
    85
41 - 51 of 51 Posts

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Super Moderator
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Also, these cars when properly garage kept, look amazing after 25 years.

My Tbird looked new when I got it; 10 years of sun has ate the paint. :(

Keep lots of wax on it, and you can avoid that; turtle wax paste is the best.

Put those cadets to use!! :D
 

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1994 Thunderbird LX 3.8
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53 Posts
True. The seller said it was his neighbor's and said that it probably was a hundred or so miles off because the odometer broke because someone reset the trip odometer while driving (really?), but it is working now, and the interior looks MINT. I don't think he'd have mentioned that unless he was on the up and up. ?

And yes, I've never been that way about my other cars, but this one needs to stay shiny ?
 

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The nice thing about these cars, they look enough like police cars that if you're coming up on someone at a hundred, they get out of the way, lol.

:D
 

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I don’t think the 3.8 will have any issues going through those hills. They are slow to accelerate, but any of the ones I had did just fine cruising down the highway. You bought the car to drive it, so drive it. If you don’t generally cruise at more than about 75 or so, a set of 4.10 gears will make the 3.8 a lot more responsive though!
 

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1994 Thunderbird LX 3.8
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53 Posts
I didn't really buy it for long road trips with the kids, but apparently the Freestyle had her fill! I'll have to take it up to Lexington VA because I miss that town. Should be a pretty good test.
 

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True. The seller said it was his neighbor's and said that it probably was a hundred or so miles off because the odometer broke because someone reset the trip odometer while driving (really?)
Uh, yes. That is the only way you can break them, unless they just break on their own. It's how I broke mine in my old T-Bird. Didn't realize the reason till later. Basically, the gears are turning as you are driving, and you lock them up by pressing the button, which ruins them.

I wouldn't buy the "100 miles off" deal, though I have seen them act up, then work normally after that. No way of knowing for sure how much one is off if it is sporadic.

Al
 

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1994 Cougar XR7 DOHC/5-Speed
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IMO the gears were probably on the verge of shattering beforehand and the correlation between failure and pressing reset at best is from shock from physically pressing it transferring through the speedometer rather than gear clash(they aren’t turning THAT fast). The gears that fail are under constant mesh with and without the reset button pressed.
 

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1994 Thunderbird LX 3.8
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53 Posts
The seller was an hobby mechanic and fixed the speedometer (seems to agree with my Google maps app speed), so it was only broken for a little while. Of course, I've been terrified to reset the trip odometer the whole time I've had the car (4 months now ?). I guess next time I fuel up, I'll be brave. I still have no clue what mileage I'm getting.

I'm sure you're right. I guess my question is really do I even turn the overdrive on when I'm in West Virginia on 77... Maybe in Charleston! And yeah, I don't intend to go faster than 75 in general. I have been goaded into it, but it's not my plan ?

Meantime... I think I have some kind of anxiety disorder bordering on insanity. ? Y'all had me switching off the overdrive coming up to stop signs on my way to work (country roads I'm cruising at 50 or 60 mph), but you're just saying don't floor it in overdrive, right?

I don’t think the 3.8 will have any issues going through those hills. They are slow to accelerate, but any of the ones I had did just fine cruising down the highway. You bought the car to drive it, so drive it. If you don’t generally cruise at more than about 75 or so, a set of 4.10 gears will make the 3.8 a lot more responsive though!
 

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Flooring it while in OD is generally considered a bad thing, and can definitely lead to breaking parts if you have enough power, but to be honest, with a stock 3.8 I wouldn't even be worried about it.
 

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1994 Thunderbird LX 3.8
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53 Posts
Lol... Less power has its advantages! I'm skimming all the overdrive threads semi-obsessively now. I'm terrified of breaking my car. I know getting hit on the interstate and this whole crazy virus thing have not helped my state of mind! Deep breaths...
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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The 4-3 and the 3-2 are by themselves kind of clunky shifts with the 4R70W in stock form. With the 4-3, the forward clutch has to apply while the overdrive band releases. If the O/D band hasn't fully disengaged by the time the forward clutch fills and begins to apply, the transmission as a whole is momentarily trying to lock up completely. That's why you often feel a "sag" during that shift. The reverse is true with the 3-4 shift. With a lot of engine torque, that means the clutches are slipping during the shifts - more torque + slipping = more heat/wear. That's bad. :)

With a 3-2, the direct clutch then has to release. This relies on the one-way clutch locking (which is a fragile design that was later replaced with a mechanical diode) - if the 3-2 happens abruptly, that puts a lot of shock load on the one-way clutch. With a fragile design, sudden load changes mean stressing what's arguably the weakest link in the early 4R70Ws, and that's bad too. :)

Something else to consider is that shifts don't happen immediately after they're commanded - there are physical constraints to consider with clutches filling/applying and exhausting/releasing. The PCM is programmed to know how long shifts are supposed to take, so it will wait what should be an ample amount of time for the 4-3 to complete before commanding the 3-2.

When you combine a 4-3 with a 3-2 (aka a 4-2), it's usually because you've gone WOT (or close to it) and need maximum acceleration at a speed anywhere from 35 to 70 or so MPH. Let's say you're cruising at highway speeds (let's say 65 MPH and 2000 RPM) and hit the throttle. So the transmission shifts to 3rd gear (and as this is happening, the torque converter unlocks to help cushion the engine from the abrupt rotational energy speeds from changing) - we wait a short time for the OD band to release and forward clutch to apply - and we're now revving up towards 3000 RPM. And as soon as that shift is nearing completion the PCM is already commanding the 3-2, which means we're now shifting all the torque of the drivetrain to that little one-way clutch and trusting that it will stop spinning for 2nd gear and 4500 RPM or so. Now consider an old, tired transmission with leaky seals and whatnot - that add up to longer shift times. That could mean the 3-2 is in progress before the 4-3 has had a chance to finish. Now that's really bad. :)

Either way you slice it up, it's an awful lot of shock to the one-way clutch because of the sudden torque increase - not only from the engine, but from the fact that there's a 3800 lb. MN12 attached to the other end of the transmission that wants to keep going 65 MPH - changing gear ratios abruptly means the transmission and engine need to change speed abruptly too, and the energy of the car moving to spin up the driveline is way more than the engine could ever deliver to get the car moving.

At least with the N/A 3.8s, their torque output is that much less than the 4.6 or SC guys, so in stock form you're much less likely to break anything in the trans. All the same, go easy with the 3-2. 4-3/3-4 is clunky and generates a lot of heat because of the nature of the shift but is otherwise (IMO) not as big a deal as the 3-2. 4-2s are just stock 4R70W killers regardless. :)

The best thing you can do for your transmission aside from a replacement with a newer model or upgrading internals is to J-mod it. That will help shifts complete a little faster - giving you some cushion with ensuring you don't inadvertently end up with a transmission overlapping shifts in progress. It also helps with keeping the gearset from locking up during the 3-4/4-3 due to the faster forward clutch exhaust/fill times.

So if that made ANY sense whatsoever, hopefully that helps you understand a little better what's going on.

For a better explanation, read Jerry's Thesis... I posted a copy in the tech articles section.
 
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