Vacuum lines on AOD?

[Medusa]

This morning I started her up, let her warm up, and she was driving just fine. Got on the freeway and hit about 55, then I felt/heard something pop open/break loose, and now it's like it was yesterday, sounds sort of "wide open," almost like the TV cable popped off again. Stopped and checked that, it's in place with what seems like correct tension, so I don't think that's the issue.

Is there a vacuum line to the transmission that I need to check? It felt like she suddenly lost pressure somewhere and now the tranny just isn't "right," but obviously this is an intermittent problem.

This vacuum line setup certainly makes things interesting :-\

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[killgore]

I believe the AOD does not have a vacuum line


That being said, I do not know much about these magic boxes behind the engine. I do think they have an internal governor however

[DerekTheGreat]

No vacuum stuff with an AOD. Could be that the busted chunky bits are rearranging themselves in the transmissions valve body and elsewhere, causing differences. Maybe now all you've got is first gear.

[Medusa]

That makes sense, but it's odd that it would improve after sitting, unless the chunks are settling overnight and then being washed back up into the valve bodies, etc.

I've got to find a better price on a rebuild.

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[DerekTheGreat]

I'm kinda confused now, I thought you said it's worse? I'm not an expert, nor do I have any hands on experience with transmissions but from shop manuals I've learned there is a lot of pressure, with nuances between manufacturers. As far as the AOD goes here's how I understand it. The torque converter is connected to the AOD's oil pump, which starts spinning the instant you begin to crank it over. It always generates as much pressure as possible (~80psi IIRC) but the TV cable acts as a flood gate or valve so to speak. The further you press down on the gas, the more you open that gate, hence "Throttle Valve." This is also why it is so important to have this working properly as it is the life blood of the transmission. At idle that pressure is reduced to 0-3 psi if everything is adjusted correctly. As you step on the gas it will increase, this increase is also picked up by the transmission's governor, which uses that to adjust shift points. Lower pressures usually mean softer & sooner shifts and vice versa. Full throttle allows as much pressure to hit the governor and mechanical bits as possible. The Ford communities seem to say that higher pressure is better for longevity.

So you can see that with little or no pressure you'll end up generating lots of friction & heat which will eventually lead to a failure. When they tore apart Ashley's transmission they told me she didn't have 1st gear because there were bits of the overdrive band and other gunk in the valvebody or servo. If you manually put the thing in 1st it didn't want to move, I remember that lol. So with all that pressure flowing around it's possible that the longer you drive it the more likely it is that the stuff may move around before finding a permanent home. Just a theory, I could be full of shit on it haha.

Edit:
Here's a cool read with pics and information about the AOD:

http://www.cartechbooks.com/techtips/ford-aod-and-4r70w-transmission-history-and-evolution/

[Medusa]

It did this same wide open thing yesterday, but after sitting overnight, it was driving "normally," post-fourth-gear-burnout normal, until I got on the freeway at 55 this morning. Then it went back to "wide open" mode, which feels very similar to how it felt when the TV cable bushing rotted and the cable fell off. But that's not the problem, cuz the TV cable is in place and under tension. I'm about to limp her home at 35mph or less, flashers on lol

From the way it felt when it switched to wide open mode, the idea that something is holding a valve body open makes sense.

Looks like DH has found a 2003 Chevy Blazer he's going to pick up for me and have running in the next couple days, so hopefully I won't be without transpo for too long.

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[DerekTheGreat]

Fourth gear burnout and wide open mode have me scratching my head lol. It's possible the cable is stuck where it connects to the transmission.

Ah, so you're trading one pile for another pile. Best of luck.

[Mainemantom]

Sounds like the OD is no more. Keep the shift lever in "little d" when driving. Get more estimates on a rebuild or a rebuilt exchange transmission.

[johnunit]

yeah I'd say the transmission is toast from the previous no-TV cable expedition, and it's juuuust alive enough to still act like it has OD in certain situation.

The TV cable falling off on the highway could toast OD in less than the distance it takes to get to the next exit.