Most A/T ...even when in high gear have a certain amount of slippage in the converter.
Just the way they were designed.
That's one reason why when doing any kind of "modifications" to these trannys a larger transmission cooler is recommended...
to cool the fluid because there will be increased slippage.

New(er) transmisions have a lock-up converter. It was done to help improve MPG. eliminate slippage should= more MPG.

Now....most (all?!) A/t's have lock-up converters AND OD gears for highway driving for even better MPG!

Can't help about the input shaft question.
I DO have an A/T in my lil parts chaser 91 S-10. It has a lock-up converter and OD. It's pretty primitive by today's standards.
I had it re-built a while back and had a Corvette servo valve installed instead of the stock one. Also had a shift kit installed to firmer shifts. (still barks the tires when shifting into 2nd gear!)
I WISH I had modified the governor while it was apart. By lightening it....the shifts from first to second are extended.
Now...it shifts from first to second at aprox. 15 MPH.! (oe less)
I'm sure that was GM's attempt at increasing MPG by going into high gear as quickly as possible. it tends to lug the engine slightly at low RPM's.
FoMoCo prolly did the same thing to their version of AOD's. I would take a look at that while yours is apart.
For "spirited" driving you would want a 1-2 shift to occur about  20-25 mph.
2-3 shifts don't have to be stretched out because you are already spinning the engine at a higher RPM.,,,, 30+ MPH!?!

My guess would be...(about the input shaft)....since your rear tire size will be limited with a 65/66 Mustang...the tires will break loose before your input shaft!!
6sally6

Lockup converters serve two functions:
1.) Eliminate slip at cruising speeds to improve mileage.
2.) Eliminate slip at cruising speeds to reduce heat generation from slip.

Lockup converters are typically more expensive as they are more complicated.  If your cruise RPM is above the converter's stall speed there's no point in it being a lockup because at the stall speed the converter IS locked.

The two piece input shaft is viewed as weak.  I've heard people say the stock one can take 450HP.  I've heard others say 600HP.  My guess is its like any other drivetrain part.  One guy has a stock one behind a 800HP engine, another breaks hardened one piece shafts behind a 400HP engine.  It'll break when it breaks.  If you are planning real power I think its worth considering, but there are also hardened two piece shafts available. 

The issue with the one piece shaft is it eliminates the converter lockup feature.  So if you want the lockup you are tied to the two piece design.  Racers don't care about lockup because the car never cruises.  Street/strip guys often try to retain lockup, and most street only guys are going to want lockup. 
 

Thank you guys for all the good info.   The car has a 95’. Stock 5.0. Which I’m not sure it’s tuned to optimum performance.  It is carb’s with a 600 street Demon.  It doesn’t run like a pre-93 5.0. But that’s another story.

Basically, my point is, it’s a stock eng.  But I do want to have a good AOD, that won’t give me problems.  I had an AOD in a 79’ F100 decades ago and I remember the planetary gears going out after one year.  I just don’t want to go through that again.

BB, thanks for offering your tools, but I’m not a mechanic and Tranny’s are very intimidating to me.  Still trying to figure out that fuel sending unit!   Lol 😆

Last edited by Ozblitz (11/12/2022 7:34 PM)

Ozblitz wrote:

Thank you guys for all the good info. The car has a 95’. Stock 5.0. Which I’m not sure it’s tuned to optimum performance. It is carb’s with a 600 street Demon. It doesn’t run like a pre-93 5.0. But that’s another story.

Basically, my point is, it’s a stock eng. But I do want to have a good AOD, that won’t give me problems. I had an AOD in a 79’ F100 decades ago and I remember the planetary gears going out after one year. I just want to go through that again.

BB, thanks for offering your tools, but I’m not a mechanic and Tranny’s are very intimidating to me. Still trying to figure out that fuel sending unit! Lol 😆

Was the AOD stock to that truck?  If so it must have been a very early model.  Most first gen ODs had issues the first couple years that were eventually corrected.  Source something from the late '80s and it should be fine. 
 

Mach1Driver wrote:

FYI, the 4R70W was the AOD with all its shortcomings fixed, and has better gear ratios. It will bolt right up to a SBF. I suggest you do some reading and compare the two.

 
Ya, was thinking you already had an AOD. I'd surely recommend getting a 4R70W of you're starting from scratch.

I refreshed an Aod to put in my Galaxie a while back.   

First I built a mount for it to that fit into an engine stand.   There used to be pictures on here but they've long since disappeared.   It was very similar to the one ultra stang made.   I probably have old pictures on my computer. 

As far as the transmission, I put in a Mr. Shift kit in the valve body.   Then I put in a Kevlar od band.  Then I put in the A servo, and there was another servo I replaced.  Think it was reverse.   They are both easy to get to.  You have to remove the pump to replace the od band.   I had bought a rebuild your aod DVD from somewhere that was a good guide.   The last thing I did was something to the govenor, but I don't remember what.   I do remember something about making sure the od band gets installed right, something about getting behind the servo pin, but overall it was easy.