AOD problem

[Heretic]

I have an 87 Vic with a 93 Cougar's AOD in it. 1-D-OD pattern. The trans will shift 1-2, then 2-3 just fine, then neutrals out in OD. At 30 MPH if I drop it to 1st is will grab and hold second, telling my the internediate band is good.

My first thought was that the valve body may have a clog or bad gasket/stuck check ball etc. I also thought the 3-4 servo may be bad, however since it neutrals I know the servo is ok as bad ones will cause the tranny to hold 3rd gear. Before I tear into the pan, does anyone have any thoughts or maybe know of a specific problem area to look for?
Thanks in advance.

[Pirate]

That transmission has two bands....the other one is the overdrive band, which is a common problem with AOD's.

[Heretic]

Intermediate and overdrive are the same band. When in manual second it uses the OD band to hold the drum to create the engine breaking effect. The trans engages manual second correctly, so the OD band is engaging and holding correctly.

[Freshmeat]

Installing my Transgo shift kit there was something to look for when installing a spring into the case (as opposed to the valvebody). Had to make sure a rooster tail was clear of something or it would neutral out instead of hitting fourth. If I could find the instructions I'd be more specific. Good luck.

[Pirate]

Intermediate and overdrive are the same band. When in manual second it uses the OD band to hold the drum to create the engine breaking effect. The trans engages manual second correctly, so the OD band is engaging and holding correctly.

Having built, oh, I don't know, somewhere between 15 and 20 AOD's, the only band or series of clutches that I know of, bearing the name "intermediate", is the 3-disc intermediate clutch (4 disc on most AODE's and 4R70W's), which attaches to the intermediate sprag (which is upgraded to a mechanical diode sprag for hi-rpm applications), which, oddly enough, does the same thing.
Now, unless I am mistaken, the overdrive band, which I have had to replace in every one of the AOD's I have built, had nothing to do with holding second gear, or engine 'breaking' as you describe. Every one of them either had both Drive/Overdrive smoked, or simply overdrive was gone.
Keep in mind that the AOD doesn't want to go into 1st gear, unless you slow WAY the hell down. It will hold manual second, but not manual first, unless you do the 1-D-1 routine on acceleration, which is bad on the AOD to begin with. The idea that manual second activates the O/D band? For engine braking? According to that statement, it would have to be throttle sensitive, and only apply when you let off of the gas. The power paths, in that the two input shafts are incorrect for that scenario to take place.....

[Mercracer]

Intermediate and overdrive are the same band. When in manual second it uses the OD band to hold the drum to create the engine breaking effect. The trans engages manual second correctly, so the OD band is engaging and holding correctly.

Sorry mang, but your OD band is toasted..... your logic is flawed..... This is AOD 101. Keep it out of OD and your tranny will probably last a while longer. If you insist on messing with it and keep it in OD, then you are assured of killing it soon......

[gadget73]

I did a little digging in the Ford Powertrain book, and basically it said when 4th gear neutrals, the band is shot, the band is mislocated, or if its slipping, it suggests blockage in the valve body passages, or bad seals on the servo cover. More than likely, the band is shot.

[Mercracer]

Intermediate and overdrive are the same band. When in manual second it uses the OD band to hold the drum to create the engine breaking effect. The trans engages manual second correctly, so the OD band is engaging and holding correctly.

When accelerating in manual second, the intermediate 1 way clutch holds bu the OD band is intended to be the main holding device. That is why it is so hard on the OD band if you use manual second while drag racing. When you are decelerating, the 1 way clutch is disengaged and freewheeling. There is enough grip from the OD band to still give you some engine compression braking when decelerating even when the band will not hold in OD.
Ford intended manual second to be used only when decelerating and not while accelerating. It allows you to move the selector from D to 1 and downshift to 2nd gear for engine compression braking. Lentech fixed this by giving us a 1 2 D pattern with an electronic OD delete.

[gadget73]

There are actually mods to the valve body with epoxy that give a 1-2-OD pattern which is nice for racing, but probably sucks if you do a lot of mountain driving. Also not sure about how much unusual abuse is placed on the trans by doing that. The electronic OD off would be totally awesome if it weren't so spendy.

[Mercracer]

There are actually mods to the valve body with epoxy that give a 1-2-OD pattern which is nice for racing, but probably sucks if you do a lot of mountain driving. Also not sure about how much unusual abuse is placed on the trans by doing that. The electronic OD off would be totally awesome if it weren't so spendy.

If those epoxy mods make the 2 position a manual 2nd position in relation to fluid flow, it is a recipe for a cooked tranny. If it is similar to the Lentech mod, then it is OK. The Lentech valve body with its 1 2 D/ODmakes the tranny stronger because of eliminating lockup in 3rd and not using the OD band in 2nd it makes manual 2nd act like automatic 2nd....

[Heretic]

When accelerating in manual second, the intermediate 1 way clutch holds bu the OD band is intended to be the main holding device. That is why it is so hard on the OD band if you use manual second while drag racing. When you are decelerating, the 1 way clutch is disengaged and freewheeling. There is enough grip from the OD band to still give you some engine compression braking when decelerating even when the band will not hold in OD.
Ford intended manual second to be used only when decelerating and not while accelerating. It allows you to move the selector from D to 1 and downshift to 2nd gear for engine compression braking. Lentech fixed this by giving us a 1 2 D pattern with an electronic OD delete.

This is what was meant by my previous statement. It seems to be fine in manual second, both accelerating and decelerating. I would think if the band was faulty neither manual second or OD would work correctly.

[Pirate]

This is what was meant by my previous statement. It seems to be fine in manual second, both accelerating and decelerating. I would think if the band was faulty neither manual second or OD would work correctly.

As I go back through my AOD terminology...
Keep in mind the phenomenon you speak of only partially engages the OD band, when you have the shifter in 1, trying to hold 2nd manual (by you throwing it back into 1 to keep it in second). If I recall correctly, the AOD is not designed to be ran in manual 2nd, by idiots throwing the shifter back into 1 to hold it there....it tries to partially engage the O/D band (PARTIALLY), while trying to disengage the 1/2 clutch pack. It's a feedback problem with stock AOD valve bodies (one among many), and is usually fixed with a proper shift kit, as the O/D band is not supposed to be applying in second gear. It does not, however ENTIRELY RELY ON THE O/D BAND TO HOLD MANUAL SECOND. Therefore, if the O/D band is toast...it will still try to engine brake in second.

O/D band is toast.

Thank you, please drive through.

[Mercracer]

This is what was meant by my previous statement. It seems to be fine in manual second, both accelerating and decelerating. I would think if the band was faulty neither manual second or OD would work correctly.

Want to do a simple check? From a stop in D, accelerate and when it shifts to 2nd, drop it back into 1. When you think that you valves are going to float, put it back into D. See how solid it hits 3rd.
With a faulty band, manual second will still "work" fine while accelerating and decelerating as the 1 way clutch will hold and the band will still be applied. In OD, a metric assload of force is required by the band to hold it in gear. If OD is not a functioning gear, then your band is toasty.

[Heretic]

Well if it needs a complete rebuild so be it. This will be yet another chunk of change I do not have, lol. Thanks guys, will need to make an appointment at a tran$mi$$ion $hop before somehting else "Brakes".

[Mercracer]

If you need it to, your tranny can live for years without OD. Leave it in D and drive nice.....