Hello, New poster, have read many threads and searched a bit looking for some info that matches what I'm experiencing. Hear goes I'll try and include as much information as I can. A little over a month ago I got a new(to me) 1983 F150 2wd, 4.9l with an AOD and 3.55 gears with a limited slip and stock wheels and tire size. I started driving the truck and immediately noticed a rumble in the truck between 45 and 60 especially with a light throttle pedal but also when on it around 55. I started with U-Jounts (the rumble got better but persisted).

Things then escalated to taking it to have the driveshaft balanced and rear inspected. The driveshaft was not out more than the normal tiny amount but was adjusted, the rear was found to have one of the clutch discs breaking and pieces migrating and causing some damage. The entire rear was rebuilt and new clutches installed. After this the drivetrain was much more quiet and the rumble between 45 and 60 with a light pedal went away.

What is still there and the reason for this question is the Rumble almost exactly at 55 and around 1500 rpm when on the pedal in OD. I confirmed I cannot make the truck make the noise in 3rd gear and above 55 in OD it will not make the rumble even when on the accelerator.

The sensation is kind if odd around 55 there seems to be very little acceleration and if you lift enough to stop the noise it almost feels like the drivetrain is more free. (If that makes sense)

I know very little about the AOD my other truck(91 F150 with a 4.9L and Mazda 5 speed) is manual. So I'm on the learning curve. I'm more than willing to dig in a learn I just don't want to throw tons of money at a Trans shop without a little better understanding of what is going on.

Is this a well known trait of the AOD for guys in the know or is this one of those odd things that happen? Thank you in advance for any help. I'll mention I plan to restore the truck it's straight has very little rust in the important areas and runs great with the exception of this issue.

 

Sometimes with slight noises like that, you just have to keep driving it till they get loud enough to find. Or it may never change and be that way forever.

 

The AOD is a delicate flower and was a problem child for the first few years of production. '88-'93 units had most or many of the bugs worked out of them by Ford. When introduced, they produced massive warranty claims.

Hunting between 3rd and 4th caused a lot of issues, and having a tall axle with an OD transmission made it a sure thing that the transmission would be hunting pretty much all the time between about 35 to 65 or better.

The "lockup" design is different--I can't explain it, but the links will give you background and more. Monitor the rumble and bite the bullet earlier if it gets worse.

https://www.hemmings.com/stories/art...d-transmission

More, with an explanation of the two input shafts:

https://www.cartechbooks.com/blogs/t...-and-evolution

Into the weeds of aftermarket modifications:

https://www.motortrend.com/how-to/hr...-transmission/

And there's more--enough to keep you busy all weekend via a search or two.

 

Thank you very much for the links! I take it my concerns of the Trans having issues are on point. It's good to know what I'm up against. I'll definitely be keeping track of everything and contacting shops local to me to find a good one to do the job. The rear main seal is leaking also so while the Trans is out that too can get fixed.

Over all I'm thrilled to have the truck and am looking forward to getting it back in good running condition. So far the only problem speed is around 55 so I'll he limiting its usage at that speed. Thank you again for the reply. If anyone has some insight on what may be the part failing I've always liked having more information than less when talking to a shop.

 

.......x2

I have an '83 F250 that had an AOD when I bought it used (originally a 302).......it failed after a couple of years of very gentle driving.
My advice would be if your current gearing would let you operate without OD, go with a C4 or C6 depending on usage.

In my experience, the question isn't "will an AOD fail?"........it's "how soon?", without modifications.

 

Thank you for the information I will looking into other options. I also was reading the AOD can be rebuilt with more robust internals, finding a shop to do that may not be overly practical though. Luckily it appears I have some time to try and do some research. The truck is unbelievably original so I'd like to keep the truck as original as I can, but if the AOD can't be reliable I'm not against functional upgrades.

 

How many miles on it and what was the service like on it?
If high miles and you dont know if the service was done as it should then I would think a good rebuild with the upgrades and proper service it will out live you.
Dave ----

 

Keep the engine and carb completely stock and adjust the tranmission linkage properly, and you will be ok. Change the engine or the carb to something that does not have the proper AOD linkage, you are sunk.

 

I have been happy with the A4LD transmission from PATC in my Bronco II. They have a stock replacement and several upgraded versions of the AOD.

 

The AOD was developed with fuel economy in mind. It is very good at achieving its design goal. The lockup 3rd and OD was the key.

With the advent of transmission electronic control, lockup features became the norm universally.

I like my AOD. If it ever craps out I have a 1988 AOD in storage to rebuild. As already mentioned, by '88, the AOD was about as strong as it ever got.

The AOD's weakness in my view is it did not tolerate abuse and depended on the critical proper TV cable adjustment.

My AOD benefits from maintenance. It has had three fourteen quart fluid changes with 135k miles.

 

The truck currently has 164,000 on it. It seems the truck has been kept up with. The transmission fluid is very clean (on the stick at least). Everything on the truck shows some age but it's all there, clean and in original condition. It does not show signs of any shacked together repairs either. I feel it's a great candidate for bone stock restoration.

 

So far everything on this truck is stock. I am reading up on the TV cable adjustment procedure and once I'm confident in it will give it a go to verify a baseline. I'll be sure to update this thread with what comes from that.

 

Awesome thank you for the information I will be looking into it!

 

It's great to hear the AOD can be reliable with basic maintenance. I will be researching the procedure to verify the proper TV cable adjustment. It seems very plausible it could have stretched a little. Out of curiosity is what I'm experiencing a sign of a cable that has too much slack in it?

 

Off hand, I'd say not.

The TV cable regulates pressure. Loose cable= lower pressure and causes clutches to slip which causes heat which causes more slip, more wear. A downward spiral until the vehicle won't move. If the rumble is indeed coming from the transmission I'd suspect something other than clutch/steel wear. The pressure also dictates shift timing which you do not complain about.

AS mentioned, since everything seems to work okay it would be hard to guess what the problem could be. Something like center support retaining ring broken comes to mind.

A simple check for TV cable: Move the throttle linkage at the carb and note that the TV cable has no slack. Goldilocks cable needs to be just right. Not loose, not tight. The cable should pull the transmission lever with any movement of the throttle.