aod interchange question

md10

Registered User
I have a stock 92 sc and the aod is not acting right. It shifts to early, will not downshift and i think it slips. So i just want to repalce it with another aod for now.

I have read that the mark vii(or is it viii) has the next best aod to use, but what year.
If i can't find a mark aod how long might a non sc 3.8 aod last?

Thanks
 
I have a stock 92 sc and the aod is not acting right. It shifts to early, will not downshift and i think it slips. So i just want to repalce it with another aod for now.

I have read that the mark vii(or is it viii) has the next best aod to use, but what year.
If i can't find a mark aod how long might a non sc 3.8 aod last?

Thanks
Any year SC AOD should work fine for you. The na 3.8 will usually have the "C" O/D servo. That's the weak point. However, if all you're doing is driving it around town andf not leaning on it much in O/D, you should get many miles out it.
 
Well, to me it sounds like the kickdown cable is not attached....my buddys SC did the same thing when the cable was disconnected..Shift through gears early and no downshift when you get on it. Depending on how long its been like that, you might still need a new tranny.
 
I've done this. A c-servo on any boost is asking for lost overdrive. If you use the na trans at least swap the servo. a v8 trans isn't that bad they have the B servo. The low end torque of boost on these motors is too much for the narrow band of most aod's. Even with an A servo the overdrive is weak.
Alan
 
I am doing this right now. I got a low-mileage AOD from a V8 1989 Grand Marquis. It's holding up fine (2 years now). I do try to make sure I don't let it shift into or out of OD with a lot of power applied, as I think I noticed a light rev flare a couple of times in that situation. I also have the TV pressure bumped up a little. Shifts are firm and seem to be timed well.
 
it was starting to give me problems so i changed the tran fluid and it went down hill from there. so what is the best year for the aod other than the SC.

So it would be best for a aod from a 5.0 car. will a f150 work?

My u-pull-it gave me a interchange list for the SC aod and some of the aods go back to 82.

thanks again
 
I would stay away from an F-150 AOD, because I think they have longer tailshafts. So do some Crown Victoria police cars. I guess you could swap the tailshaft, but I don't really know if that works, or how involved it is.

There are some minor differences even in the transmissions that will fit. The ones from a Mustang, Capri (maybe also Fox T-Birds), Crown Vics and Grand Marquises have a different shift lever on the side of the transmission. You should swap it for an MN12 Thunderbird one. Also, the rpm governor is different depending on the application. Mustang AODs probably have a high-rpm governor, so they tend to shift higher. Transmissions from granny cars like my Grand Marquis have a medium or low-speed governor, so they will shift lower. You can't totally change that with a TV pressure setting. You can, however, swap the governors to get the one you want.

Also, I have heard that pre-1988 AODs are less reliable. I don't know all the details.
 
You can, however, swap the governors to get the one you want.
Unless you're in Illinois. :D

You must mean the valve body. The shift points are determined by the springs internally. You can either swap for a different VB, or install a shift kit to change the shift points and firmness.
 
Unless you're in Illinois. :D

:p

You must mean the valve body. The shift points are determined by the springs internally. You can either swap for a different VB, or install a shift kit to change the shift points and firmness.

No, really, there's a governor in the rear of the transmission. As I understand it, the governor has springs that work against the centrifugal force of a weight. The balance between the centrifugal force (increasing with speed) and the spring rate (constant) determines the flow of hydraulic fluid through a valve. The pressure difference between that fluid and the TV pressure determines when the transmission shifts.

(Not that the valve body is irrelevant.)
 
i've been driving it more and it shifts through the gears to fast almost just skipping second(with more than half throttle) and then skipping third if its in OD. i have to have it in D or i'll end up in 4th at 1000rpm.

I was thinking of taking the valvebody off and cleaning it. Does anyone think that will help any?

How about the 4r70w, are those built better even if its not from a supercoupe and i know i would need a controller but i think that would be the better option in the long run.

Thanks
 
4r's have soe distinct advantages. You can either swap what you can into your aod or put a manual valvebody on the 4r.
Alan
 
No, really, there's a governor in the rear of the transmission. As I understand it, the governor has springs that work against the centrifugal force of a weight.
Actually 1 spring.
The balance between the centrifugal force (increasing with speed) and the spring rate (constant) determines the flow of hydraulic fluid through a valve.
The govenor provides pressure proportional to vehicle speed.
The pressure difference between that fluid and the TV pressure determines when the transmission shifts.
Sort of. The TV pressure is balanced against the govenor pressure. When Gov pressure exceeds TV pressure by some amount, an upshift occurs. Conversely, when TV pressure exceeds Gov pressure by some amount, a downshift occurs.

All of the shift decisions are made in the valve body. If I were a builder of an automatic tranny for a range of vehicles and driving, I would "tune" its shift characteristics with VB springs, rather than with a separate govenor.

On the other hand.. with the Gov, its just 1 spring that might be easier to get to if all that would be different is the speeds at which up shifts happen. The firmness of the shifting is not controlled by the Gov.
 
Back
Top