Hello Everyone, Looking for a little tech info on an AOD trans, it is in a 90 Cougar LX with a 3.8 V6, it has <67k original miles and has sat most of the time for the last 10 yr.

This car was a freebie and has plenty of life left but has 1 issue, When shifting into Overdrive it does not catch at all. All of the other gears have a solid engagement. One of the companies that specializes in this tranny indicated it was either wore out which I'm inclined not to believe due to the fairly low miles on it. The other cause as they stated would be the servo that controls the shift is not functioning.

IF it is the servo can anything be done to massage it, test it, or otherwise get it to work again. I have not changed the fluid or done anything so far. Would a Professional Flush help or do I have to just pull it and spend a grand I don't have to fix it?

Any info, diagnostics or tips and tricks would be great!!

Happy Thanksgiving

Mark J.

 

I would suggest you drive it for a while. One on the pistons in the valve body may be sticking because of sitting. Maybe you should consider a new tranny filter and fluid. There are all kinds of "mouse milk" (I dont have a clue where I heard that term ) that loosens up the gunk, but I would hesitate to use any of the stuff. I dont think you will hurt a thing by driving it, I bet it will, one day, just start working. If nothing works, worst case is that you have no OD. Thats still cheaper than a repair---that $$$$ will buy a lot of gas. Another worst case is that it will never work and will one day just quit altogether. Then, you are about where you are now, needing a tranny rebuild, except that you may get many miles of good driving and use out of it first. Sounds like it may be a really nice car and a good find. LOL

 

Sounds like pretty reasonable advice. I had driven it about 300 hundred miles to & from work but after I realized what it was doing decided to park it for awhile till I could be sure I was not hurting it more.
I got the impression the servo or at least part of it is accessible through the pan and valve body, I was hoping I would be able to get a little more info on the servo, maybe find out if there is a moving part or which holes the flow comes through or even better if you can physicaly move it back & forth. Also since I will at least change the fluid & filter, is there a better fluid than the stock recommendation?

Thanks for your response it is appreciated!!

 

There is a manual made by ATG or ATSG thats gives a lot of pictures and info on many transmissions. They are available for each specific tranny. I have one around here somewhere, but cant put my hands on it for now. I have put shift kits in the AOD's and rebuilt several, been a while though. There are about 3 cover plates on the bottom of the valve body for servo pistons, but I just cant recall if one of them is OD, dont think so.

Al local parts house should have the ATG manual or maybe a parts supplier (yellow pages). I got mine several years ago from a "DACCO DETROIT" company locally. The manuals arent expensive, just a paperback. I will look for mine-----. It isnt really too difficult to change oil and filter yourself, just a little messy.

 

I may have given you a little bum info earlier . Seems my memory is like a steel sieve. Yes, there is an OD servo. They are rated by letter A,B,C. A is the largest diameter and applies the most force on the band ieerformance use. Most cars had the B servo----. I know for sure the SuperCoupes (superchgd 3.8 ltr T-bird) had the A servo. Not exactly sure what else had them, so I wont guess. The aftermarket makes even larger ones with other I.D's (such as A++). Depending entirely on your planned use, choose one. More than likely the one in the tranny is just stuck because of sitting, hopefully an oil feed port isnt varnished over. They are actually simple to get out and clean. Even in a stock motor, if you replace the servo I would go with an A because it will give a firmer OD shift.

I suppose the band that the servo applies could be worn out or disintegrated, in which case it could be scoring the drum----not good! Look for metalic material in the pan---probably in the goo in the bottom. If the servo seems to be free, then thats more than likely the case.

Google "ATSG Manuals" and one of your hits will lead you to a parts supplier and a pic of the servo. You may even find an on-line proceedure manual. I will look for my manual, but I think you can get to the servo with the pan off, without having to remove the valve body. Dont know if you are mechanically inclined and wish to do it yourself.

 

Very good, the manual is a great thing to have it would probably keep me from getting to lost. Think I will drop the pan to see what kind of debris is in the bottom hopefully not much. That should tell a little more of the story. My guess is that it is just stuck as the car was used pretty much in town, over the last 10 yr he average a little over 1k per year. Pretty sure the tranny fluid was never changed so it is nearly 20 yrs old.

I'll post the results to let you know what I find.

Thank you so much for the info!!!