Stall convertor question - Lock up or non lock up w/ AOD

68 & 00 GT · Jan 5, 2004

I'm having a very nice AOD built as we speak for my 68, and I'm wanting a 2,500 stall but I'm not familiar w/ the pros, and cons of the lock up vs non lock up features.
Is a 2,500 stall 'bout right ?
TCI, and Huges seem to think I'll be happier / better off with a non-lock up. They think I'll loose power / efficiency with a lock up, but I thought a non lock up will still slip on the highway. Is that just a trade off ?

Anyone care to enlighten me on this.

Thanks-

BTW- I'm running a 302 w/ a mild cam.

1968 GT Coupe
Already restored,
302 w/ mild cam (rebuilt)
3 speed auto.w/ B&M shift kit.(rebuilt)
Pertronix ignition w/ 7mm wires Bosch platinum plugs
Carter 4bbl carb.
Edelbrock performer intake
Hooker Comp. LT headers
2 chamber flows 3 in. exhaust
4 row radiator new A/C system (R134A)
17in Edelbrock 454 wheels
Magna front 1in. lowering springs
Magna 5 leaf rear 1in. lowering springs
KYB adjustible shocks
Chrome strut tower support brace
GT 350 front sway bar
Eleanor front end / grills
67 Shelby hood
67 Shelby tail lights

dodgestang · Jan 5, 2004

68 & 00 GT said:
I'm having a very nice AOD built as we speak for my 68, and I'm wanting a 2,500 stall but I'm not familiar w/ the pros, and cons of the lock up vs non lock up features.
Is a 2,500 stall 'bout right ?
TCI, and Huges seem to think I'll be happier / better off with a non-lock up. They think I'll loose power / efficiency with a lock up, but I thought a non lock up will still slip on the highway. Is that just a trade off ?

For any kind of high horse power application you want a non-lock up converter. I run an AOD behind my 408 stroker with a one peice inout shaft and 3000 stall converter. If your motor is not going to produce any power below say 2500-2800, you will want the non-lock up simply (as I understand the principles) you will not have ANY power as soon as you get into 3rd or OD if you do not have the RPMS high enough to where the motor makes power. That means if you are crusing on the highway in OD at say 1800 and kickdown to pass which might raise the RPMS to 2200-2300 until your motor gets up into its power band the car willl be a dog.

If you run the non-lockup even in 3rd and OD the TC will be applifying until you get above the stall speed. What that means is, when you are running around on local streets you should be driving in 'D" and never going into OD (shifter posistion) to keep the RPMS a little high to keep excess heat from being generated...when cruising on the highway you then use OD and even if the RPMS aren't above the stall speed the cooling system is getting enough air to keep it cool. If you are not upgraging you radiator at the same to high flow aluminum unit with a tranny cooler, even if your 4 core brass unit has AT cooling, you will want to add an external cooler as well strapped to the front

68 & 00 GT · Jan 5, 2004

Cool thanks for the info -
Forgot to mention I have a B & M trans cooler ready to go with it all.
I don't plan to make my engine very highpowered at this point. I want to be able to daily drive my car. Only additional mods I may consider are some nice aluminum heads. My car makes good low end power as is. It's not a high reving motor, and doesn't require high rpm's to make power. It's pretty smooth power delivery through out the rpm's I just want some extra take off power.

That being said what is the difference betwen lock up, and non lock up ?
Does the lock up slip the rpms' in all gears but OD , and the non lcok up slips the rpm's in every gear ?

The way I see it neither should / will slip the rpms past the desired stall speed right ?

I'm so confused - Please help me here guys.

12sec67 · Jan 5, 2004

the only difference i know of is that you would get better gas milage from the lock up converter and better performance from the non-lock up. i'm running an art carr 2500 non-lock up stall speed through a built AOD with a one piece input shaft like dodgestang.

love your car by the way-i have the c/s deck lid too. it sure does add a lot of character to the body!

68 & 00 GT · Jan 5, 2004

thanks for the compliment. CS lid is a nice addition

Still don't understand what a lock up does, or what a non lock up doesn't do.

Anyone ?

Fostang · Jan 5, 2004

It makes an auto tranny that will never be say 1:1 in 3rd as a 5 speed would be in fourth gear closer to 1:1 ratio.

I went non lock up one piece shaft and a bunch of other stuff including a wide ratio kit.

68 & 00 GT · Jan 5, 2004

Huh ?

What are the pros and cons of each ?

Sorry for all the questions. I want to get this right the first time.

mustang70 · Jan 6, 2004

The lock up converter has clutch inside that engages at some point. Usually in OD. The non-lock up converter doesn't have this clutch in it. One bad part of the clutch is that everytime it engages a little bit of material is sent into the tranny. Also, when a converter is slipping, it's providing a some torque multiplication. With a lock-up, you loose that mulitplication when the converter is locked.

I think you should get a non-lock up converter. The two piece input shafts on the AOD's are known for being weak, so I think going to a one piece is a must. As for the RPM's, there's really only a couple hundred rpm difference beween lock up and non-lock up when they're in their rpm range. As for cooling issues, I don't think you'll have a problem as was said before.

That's just me though. Sorry if it doesn't make sense, it's been a long day.

rmrfstar · Jan 6, 2004

What are the pros and cons of each ?

Lock-up: Two piece output shaft. One piece of the shaft is connected in the standard way a torque converter works, creating torque multiplication, slippage and heat. The other piece of the shaft is directly connected to your motor, no multiplication, no slippage or additional heat. In lower than OD gears, the AOD uses the standard output shaft. In OD, the AOD engages the directly connected shaft and therefore increases your transmission efficiency, working much like a manual transmission.

Pro: Higher efficiency at freeway speeds, higher gas mileage, less transmission heat.

Con: Two piece shaft has less strength, more susceptible to breakage at higher HP.

Non-Lockup: One piece output shaft. Connected to motor in the standard torque converter fashion, functionally the same as a C4 torque converter.

Pro: Torque multiplication in all gears, much stronger - can withstand more HP.

Con: Lower efficiency due to constant slippage at highway speeds, lower gas mileage, more transmission heat.

Well, I think that covers it. If you plan to race, then go non-lockup. If you will have a daily driver, spending time on the freeway, go lock-up.

I got the parts to install my AOD for christmas, crossmember, shiftkit, TV cable. I spend too many miles on the freeway myself, so I am going to keep the original lockup 1,800 rpm torque converter. I will probably get a 2,500-2,800 stall lock-up when $$ permits.

68 & 00 GT · Jan 6, 2004

Thanks for all the info. It seems I can get the lock up and not have a stall in over drive (which is what I want), but then I have the two piece input shaft that is notorious for being weak, and the clutch releases material into the transmission when it engages too.
I like what the lock up will do for me, but the non lock up sounds better for my transmission. Kinda seems like the main pro with a lock up is increased gas mileage. If that's the main one I think I can live w/ a non lock up.

What is a non lock up like in OD ? Same as all other gears it slips untill after the stall rpm ? Do I have to floor it to get it moving, or is it not that drastic, and wil still pull with less throttle, or more so b/c of the stall ?

Oh one more thing. What kind of horsepower are the lock up's really good to with the 2 piece input shaft ?

dodgestang · Jan 6, 2004

68 & 00 GT said:
Thanks for all the info. It seems I can get the lock up and not have a stall in over drive (which is what I want), but then I have the two piece input shaft that is notorious for being weak, and the clutch releases material into the transmission when it engages too.
I like what the lock up will do for me, but the non lock up sounds better for my transmission. Kinda seems like the main pro with a lock up is increased gas mileage. If that's the main one I think I can live w/ a non lock up.

What is a non lock up like in OD ? Same as all other gears it slips untill after the stall rpm ? Do I have to floor it to get it moving, or is it not that drastic, and wil still pull with less throttle, or more so b/c of the stall ?

Oh one more thing. What kind of horsepower are the lock up's really good to with the 2 piece input shaft ?

It has been my expereince that it is something you do not notice.

rmrfstar · Jan 6, 2004

68 & 00 GT said:
...the two piece input shaft that is notorious for being weak, and the clutch releases material into the transmission when it engages too.

So google tells me, only the later(after aod) ford over-drive transmissions have a clutch. I thought that the aod was directly connected, but mustang70 said that it had a clutch. So I thought I was wrong, anway it was 3am and I was tired. There is a clutch in the AOD-E/4R70W, but not in the original AOD (Sources Here and Here.)

The AOD-E/4R70W has a one piece output shaft TC, and uses a clutch to lockup the torque converter.

The AOD has a two piece output shaft TC, one shaft connected through fluid and one being direct drive.

"If you have a serious power plant which operates in the 400-plus horsepower range", then the non-lockup single shaft converter is the way to go (Source Here.) "notorious" is the wrong word IMHO, makes it sound like the stock TCs should be breaking all over the place.

You will not have to floor it to get moving, with a higher stall.

Edbert · Jan 6, 2004

No hijack intended, this is related to current discussion...

I am now confused by the one versus two piece input shaft talk. I always thought the weak link in the AOD was the lack of a SOLID input shaft. Is "solid" what is meant by one-piece? Then a two peice is not necessarilly hollow is it?

My AOD has a 27-2900TC with a "solid" input shaft. Does that mean by definition that I have a nn-lockup?

Fostang · Jan 6, 2004

If the tranny has a one pice input shaft then yes it is a non lock up.

Yes the 2 piece is hollow one shaft goes inside a bigger shaft and the one pice is just one solid piece of shaft. he he heee

Stall convertor question - Lock up or non lock up w/ AOD

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