ford aod/4stb ???
I don't know of anyone making an 8" lockup. They may be making one but I'm not aware of it. That would be a question better asked to Circle-D or FTI, they would probably have better insight.
8" is usually a race only unit and at the level an 8" is used, lockup typically would not be.
My understanding is that in serious racing applications, using a lockup somehow affects efficiency within the converter due to fluid flow characteristics.
I've never really thought to ask any of the converter experts why this is, maybe our resident experts will chime in.
Some of the advantages to using an 8" are weight savings and the smaller diameter has less "moment of inertia" effect.
Adding the weight of a lockup piston to this may be part of the reason you don't see 8' lockups.
That said,
you could build an 8" type lockup AOD converter. The AOD doesn't use a clutch.
It has two input shafts. One shaft and another "tube" around the shaft. When it shifts to 3rd, the tube becomes a direct mechanical connection to the converter cover and effectively the crankshaft.
However, this is one of the AOD's biggest weaknesses. Most serious AOD's go to a one piece input and non-lockup.
If I were building an AOD style unit, I would use a 4R70 with the desired ratio and run it with a standalone box. It gets you away from most of the inherent weaknesses in the AOD predecessor.
The money you would spend to build the AOD with 4R70 parts upgrades is better spent on the controller and in the end you have a stronger/more functional unit.
I've learned that lesson on a personal project.
8" is usually a race only unit and at the level an 8" is used, lockup typically would not be.
My understanding is that in serious racing applications, using a lockup somehow affects efficiency within the converter due to fluid flow characteristics.
I've never really thought to ask any of the converter experts why this is, maybe our resident experts will chime in.
Some of the advantages to using an 8" are weight savings and the smaller diameter has less "moment of inertia" effect.
Adding the weight of a lockup piston to this may be part of the reason you don't see 8' lockups.
That said,
you could build an 8" type lockup AOD converter. The AOD doesn't use a clutch.
It has two input shafts. One shaft and another "tube" around the shaft. When it shifts to 3rd, the tube becomes a direct mechanical connection to the converter cover and effectively the crankshaft.
However, this is one of the AOD's biggest weaknesses. Most serious AOD's go to a one piece input and non-lockup.
If I were building an AOD style unit, I would use a 4R70 with the desired ratio and run it with a standalone box. It gets you away from most of the inherent weaknesses in the AOD predecessor.
The money you would spend to build the AOD with 4R70 parts upgrades is better spent on the controller and in the end you have a stronger/more functional unit.
I've learned that lesson on a personal project.
Teching In
Joined: Mar 2011
Posts: 12
Likes: 0
How does a 4L80e hold up if an Optishift is used instead of going with the valvebody mods to keep automatic functions?
Do internal mods need to be done also to the valvebody if Optishift is used?
Will a 4L80e with clutches and an optishift hold up as well as one with clutches and a manual valvebody?
Do internal mods need to be done also to the valvebody if Optishift is used?
Will a 4L80e with clutches and an optishift hold up as well as one with clutches and a manual valvebody?
Registered User
Joined: Apr 2022
Posts: 1
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From: Ny
