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That AOD needs some help. You have done some correct things with fluid, filter, and TV bushing. But the bushing gone is likely to be why it has no OD. So forget 4th gear for now, the shift timing is the big deal, and that is probably from debris in the VB, or the governor or its passages. The governor on the tail shaft has great affect on shift rpm's.

The gauge in the dash is for water temp, not ATF. 270* is way high for the engine temp. Forget OD for now, if you don't fix the shifting issues, the other gears will be lost and then the trans must come out. So drive it easy, stay out of the gas, WOT is the fastest way to ruin it if there is any slippage of any kind.
 

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A stock AOD car, if you drive it at a constant 30mph, should be in 3rd gear, and with very little gas it should shift easily into 2nd. It shouldn't take much pedal to make it downshift.

You can adjust the TV cable manually, but never do it by "loosening" the cable(adding slack to it). Shortening the cable with the adjustment raises the TV pressure, which firms the shifting and raises the shift rpm slightly. You can shorten/firm the TV cable(shifts) as you like until it becomes too harsh for you. But that will not damage the trans, going the other way is like having no bushing, that will kill it.

If you take that adjustment block loose(remove the tiny plastic locking pin from it), you better have first marked the plastic cable carefully so you know where it began. It's a decent idea to adjust the cable shorter by a good 1/8" or more to begin. But if it has already been altered, just know it may need more to get it back to the proper psi range.

The proper TV pressure is about 33psi with the proper checking tool installed(it pulls the cable tighter while at idle, for the test). You can replicate that tool with a simple "X" bit, though that is hard to hold in place between the cable end and the housing etc. I measured that about 24 years ago with the proper tool that I used on my first 91 Mark VII. The proper tool just slips over the cable after you pull the end(TB opened). But you need a pressure gauge on the TV port to check that.
 

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I would bet that at least the VB has to come off again to hunt for more debris, but also the governor might need to be cleaned out.

The 4th/OD gear should be obvious to be working, or not, in OD. The shifting sounds very messed up, so the OD is meaningless until you can get it to shift better in 1st-3rd. If the OD is gone, you will want to rebuild it. But if it turns out to be okay, you might be fine to install a VB kit and various Sonnax parts, plus accumulators etc. The clutches could be okay if the TV cable wasn't off for long, but the seals are very old and a rebuild could still be wise.

I have a 92 Mark VII with just 53k miles, soon I will get the cooling system and steering fixed, to drive it again. I wouldn't trust a low mileage trans that's 30+ years old. I'm swapping to a 4R70W next year at some time, I like the AOD's but they are weaker and not that good when there are issues.
 

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The TV cable is an additive pressure source, it must contribute to the line pressure at anything above idle. The setting process is with the throttle opened slightly, by the thickness of the "X" bit holding the TV cable shorter than stock. So it's checked with the TB at idle, and the tool pulling the TV cable tighter by the proper amount.

Typically a stock AOD with a 302 HO engine will shift around 4500rpm, and slightly lower at each higher shift. The HO models had the highest shifting governor(on the tail shaft), it's a tiny counterweight device that affects the shift points. I had a TransGo HD kit in my first Mark VII, and had it shifting at 5600(302 had Edelbrock heads and intake). The 2nd to 3rd shift was at maybe 5200rpm, rarely a little higher.
 

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The TV cable is critical, but more so at high throttle, so a mild cruising with the bushing gone, for a short while, won't burn up the clutches or bands.
 

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The TransGo AOD kits are the best VB kits available, both are very helpful for all conditions. The HD kit is more extensive and has far more responsive shifting(to throttle input), the ability to raise the shifts a few hundred higher, plus the possibility of much harder shifts, plus being able to hold in each gear better. Nothing will enable the OD to survive WOT, never push it in OD or past the shift point in 3rd.

The TransGo was wonderful in my first 91 Lincoln, I loved driving that car with it. I had the shifts set at the medium level, which was notably firmer than stock, but not harsh at all. That one took some extra time to install, including the long transfer tube into two drilled holes in the VB housing. I have that trans at home rebuilt, with extra shifting rpm done to it(never tested of course), with the wide band parts installed, blue clutches, Kolene steels etc. I never got to use it, and will be taking it apart soon to get the obsolete(bought new) AODE sun gear shell out of it. I'm going to install that into my 4R to make it close ratio(same as AOD and AODE).
 

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Watch your coolant temps, it's likely the car needs a new thermostat, all the hoses, and maybe a fan clutch and/or fan. Over heating the engine would be worse it if blows a head gasket, don't let it get too hot for very long.
 

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I would go through the cooling system to bring it up to new conditions, the fluid, hoses, and thermostat. If there is any air showing under the cap, I'd replace that too. It's hard to say what is raising the temp, given the unknown parts and their age. Don't assume it's all like new and guess at a head gasket, first be sure they are all good. I'd do the fan clutch also if it's not clear that it forces a lot of air through the radiator. Most issues come from one or more of those basic parts.
 

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The stock idiot gauges are okay as long as you know where the normal range is for them. Typically the coolant should run near the middle of the gauge, slightly above that is common and normal. The upper line of that range is where you should worry, that's likely in the 250* or more. Add Water Weter or another more expensive additive, those that improve heat transfer. The running temperature will drop a little with those.

If the intake has to come off, I wouldn't put an HO intake back on. Find an Explorer intake(GT40) from a 1996-2001 302, those are a big improvement over the prior intakes.
 

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Sorry for my absence, I had some stuff come up.

Whenever I start the car and let it idle and warm up, letting it idle for 1-2 hours, the temp only reaches the middle of the gauge (I start the car and warm it up every weekend). It only goes above that whenever it is in overdrive, and it reaches near the top of the gauge within 10 minutes in od. In drive it stays at around the center, usually around 1 notch above, way better than overdrive's ~4 notches above. The whole situation is very strange and as I have been using drive only, it has never overheated. The whole situation is wierd. I suspect that overdrive overheats because it is at around 3,500 rpm at all times, but I am still puzzled by this.
That 3500rpm is way too high to be cruising at, that is not in overdrive(4th gear). The rpm at 70mph should be around 2000rpm cruising, with 3.27 rear gears and stock tire sizes.

Why would you let it idle for 1-2 hours?

The AOD is a reliable transmission when it's in good shape, and not abused or neglected. Yours is not functioning properly from what has been described. The valve body is a likely cause, as also possible the modulator. The clutches still might be okay, but as you drive it with it malfunctioning, that chance is dropping very fast. The shifts should not be slipping, or really slow, or really soft, firm shifts are the best, they result in less slipping of the clutches. Hard throttle is bad for the shifts, if the shift is slipping, don't be doing it at WOT or heavy throttle.
 

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I think it's safe to say that the AOD is done, time to stop driving it and get it rebuilt. Driving anymore will create excess heat and begin to damage the internal hard parts which generally do no need replacing. So stop driving it at all, letting it idle won't hurt it but any driving to 2nd gear speeds will be adding to the rebuild costs. A rebuild kit and torque converter is around $400-$500 depending on current prices and your sources.

If they have to replace drums and other hard parts inside, add another $400+ and expect future failures before a normal service life. So stop driving it now, the costs will be much worse if you keep doing it.
 
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