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UPDATE!!!! AOD idle pressure much too high


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Ok guys, I need your help urgently.

 

The AOD is in the car, Lokar tv cable and everything else is in place.

The trans has been freshly rebuilt and has a B&M shift kit installed.

 

The instructions say to use the spacer on the tv cable and adjust it so that the pressure is 35 psi, idling in neutral with the engine at operating temperature and the trans oil luke warm.

 

Now it gets funny. Our idle pressure is 80psi!!, even with the tv cable fully loosened and no pull on the trans lever. Moving the tv cable doesn´t make any difference at all, only hitting the accelerator makes the pressure go up a little till about 85 or 90.

We are using the correct port to measure the pressure (the middle one on the passenger side) as depicted in Lokar´s literature and on numerous photos online.

 

We did of course not drive the car but the trans easily and crisply shifts into all the positions (PRND21) when I move the shifter.

 

Oil is at max level (Mercon V).

 

What´s going on here?

Did I buy a trans that´s toast?

Problem is, we have a deadline of two days to get it working.

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Mike
"If I were you...... I´d rather be me." 😛
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You know how the AOD traditionally uses a push/pull rod connected to the linkage? There is a spring inside the tranny that is there in case the linkage seperates.

 

Sometimes, there is not enough return pressure when using a cable.

 

You can try to remove that spring to see if that helps. If not, you may need to fabricate a spring to return the link lever at the tranny to reduce pressure.

 

Sounds like the tranny thinks you are stomping on the gas, even when the throttl ereturns to idle.

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We removed the oil pan once more to check the linkage inside the tranny and it works fine. The spring inside pushes the lever all the way forward against the pull of the tv cable and you can clearly see it go back to "0" ( and hear it when the oil pan is on. )

This linkage operates a "threaded cylinder" (for lack of better words) that plunges back and forth.

You might have a point with the tranny thinking I´m on the gas. What would cause this?

Could it be that there is something locked that makes that the tranny does not "see" this part working?

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Mike
"If I were you...... I´d rather be me." 😛
Check out my video:
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When I installed an AOD in my 69 vert, I spent a lot of time trying to get it right. Same setup, Lokar cable, TCM AOD with shift kit. I seem to recall it was recommend to have only approx 5 lbs when idling in park or neutral and 30 lbs with moderate gas pedal in drive. I tried using the spacer and had no luck - pressure was too high (like you have). It caused it to stay in 1st up to about 45mph and then (sometimes) it would shift to 2nd....never got to 3rd and 4th when it was like that.

 

I had a friend come over who has 40 yrs+ experience in rebuilding trannies (he has his own business). He never looked at the pressure gauge I had hooked up. He got in the car, put it drive for a few seconds, then put it park. "Back off the cable" he instructed. I did; and with wrench in pocket we went for a SLOW drive down the street. We pulled over every couple hundred feet whereas he instructed me to "back it off a couple more turns". Finally he said, "put 1/2 turn on the cable tension nut and that was it. I was sweating bullets since my understanding was you could trash the AOD within a half mile orso if the pressure was not high enough. What he explained he was looking for was for the transmission to upshift into 2nd gear at 12- 15mph with only a minimum of gas pedal pressure (slow cruising). Then for the AOD to shift from 2nd to 3rd at approx 25mph --- same mild/moderate gas pedal. Finally, the shift from 3rd to 4th was to occur about 42- 45mph. Once you have the transmission shifting at those points, you're done. Punching the pedal after doing the initial setting results in instant downshift and lots of action...

 

Since then I put over 2500 miles on it with no problem. At 2000 miles I changed the fluid and filter which involves disconnecting the cable and dropping the pan. So I had to re-set the cable position which turned out to be relatively easy knowing what I was looking for and that I marked the cable when I removed it. I actually have a bit of slack in the cable when idling in park or in drive. My pressure gauge reads "0 lbs" at idle.

 

Now, after having said all that, there is one other possibility. A number of years ago somebody (TCM?) came up with an AOD valve body that is fool-proof. It automatically sets the right pressure. The cable tension only sets the shift points. I've never been able to find out if TCM included that in the build of my AOD and since everything is working the way it should, I have not spent a lot of time searching for an answer. You may be able to find out by contacting whoever rebuilt it....my recollection is that the valve body is about $300 or so for the unit.

 

Hope this helps.

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Hello Bill73Ragtop,

 

Dude! I believe this is what you are talking about!

 

http://www.tciauto.com/tc/tcir-1980-93-ford-aod-constant-pressure-valve-bodytmhtml/

 

The new TCI® Constant Pressure Valve Body™ is now available for any stock or aftermarket 1980-93 Ford AOD transmission.

 

This cutting edge new product eliminates the most common installation error made by pros and amateurs alike – improper TV cable adjustment. When the cable is left either unhooked or incorrectly adjusted, the internal clutches and bands slip, causing great internal friction and loss of transmission efficiency.

 

The TCI® Ford AOD Constant Pressure Valve Body™ avoids all of those problems by ensuring proper line pressure, regardless of TV cable position, type of cable brackets or carburetion system. Until now, the TV cable adjustment on 1980-93 Ford AOD transmissions required a substantial amount of mechanical knowledge and ability.

 

Installation of the newly designed TCI® Ford AOD Constant Pressure Valve Body™ allows proper operation while removing slippage, thus avoiding common transmission destruction. While the TV cable still needs connection for proper part-throttle transmission shift operation, the TCI® Ford AOD Constant Pressure Valve Body™ allows more freedom as line pressure is fixed so that there is no chance of a low line pressure condition and the resulting damage to your transmission.

 

Wow, where was this when I was rebuilding my AOD?

 

mustang7173

Thanks,

mustang7173 🇺🇸

"Courage is being scared to death but saddling up anyway" -- John Wayne

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Bill, thanks a lot for your input.

But the problem is that even without the spacer the pressure starts at 80 psi. There is no room for calibrating anything as it runs on full pressure from the start.

Or am I missing something?

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Mike
"If I were you...... I´d rather be me." 😛
Check out my video:
http://www.7173mustangs.com/thread-my-mustang-in-action

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The valve body that Mustang7173 links to is what I was referring to. For the price, if I ever have to rebuild an AOD, that will be a must.

 

Luxstang: I do not know what is causing your excessive pressure, but IMO and experience, 85 psi is too high for initial setting. Can you contact a transmission specialist to discuss it? Sorry I can't offer more productive advice on what might be causing the problem.

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I talked to the guy who did my install, and here's what he had to say (my best paraphrasing, given I'm really clueless):

 

He said that if your oil pressure is reading fairly constant no matter what the TV cable and TV valve are doing, then it has to be in the valve body somewhere, most likely the pressure regulator valve being stuck. There is a spring (or maybe 2) that returns this valve to its closed position. There could be an issue with the spring, or something may be causing the piston to stick.

 

If your pressure does increase with throttle, then really look at the TV valve, and be sure it’s closing all the way (or far enough to reduce pressure). He said it can look like it's working because the piston moves back and forth, but that the cable may be inserted too far, making the position of the TV valve be always too far in the open direction…. Meaning it moves back and forth, but it is always too far in.

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Ok guys. Thanks a lot for your input.

The problem is still I solved but we learned a few things that will probably help pin it down.

I've learned once again why I like this forum so much. Thanks!

Unfortunately we have run out of time and it won't be till February before we can look into it any further.

My friend is leaving for Florida and the car is locked up in his shop until he returns.

If anybody has more info I will gladly listen to it though.

But no testing or measuring till mid February.

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Mike
"If I were you...... I´d rather be me." 😛
Check out my video:
http://www.7173mustangs.com/thread-my-mustang-in-action

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  • 3 months later...

UPDATE: my buddy's back from FL and after removing the valve body he found a few valves that were stuck He fixed that , put everything back together and the pressure was perfect.

Tv cable adjustment is done too and he took it for test drive and everything seems to work like a charm.

I have not yet driven it but it seems the problem has been resolved.

It took a while to find out what to look for though. And then there was his 3 months absence but now it seems to work.

I will post a detailed thread on everything we have done, the exact parts needed for the conversion (and the ones I bought but did not need despite of different info on the net) and other details I might think of.

Thanks to everyone who contributed to this thread and tried to help.

:)

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Mike
"If I were you...... I´d rather be me." 😛
Check out my video:
http://www.7173mustangs.com/thread-my-mustang-in-action

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