Need guidance on selecting Stall Speed for convertor

[BobCarter]

I want to be sure my 351W and AOD transmission are properly coupled and that I will take proper advantage of the engines power curve. My MKIV will be a driver and not built for the track (racing). The center section will more than likely be fitted with 3.55 gearing and I will (usually) drive at normal speeds (city and highway). I'm building a 20th Anniversary Roadster that comes with 18" rims but I have not selected final tire sizes for the car. Engine builder is Engine Factory, they are also suppling the convertor and AOD transmission. They have a lot if customers who have purchased from them for their FFR builds so I'm sure they will build and supply good stuff. Here is my question- How can I ensure that the convertor will be selected correctly by them? I know just enough to be dangerous so...
I welcome all comments and am in need of guidance.
Thanks

[wallace18]

In the recent Duplicolor 33 build on Powernation TV they used a 3000 stall unit. FFR was involved on that build.

[NukeMMC]

Good timing on this, as I am considering an AOD swap into my 68 GT350, and have been doing some research. Here is good info from Speedway on Torque Converter selection (http://www.speedwaymotors.com/Tech/transmission-how-to-choose-a-torque-converter.html). It all depends on application and what you whole powertrain is. Basically for a lightweight street car with a small block, I would be looking at a sub-2500 rpm. Stock is 1600-2200, and I would probably stick with that unless you plan on doing dragstrip launches, where you want to load up the engine before you come off the brakes.

Something else to consider is that the AOD torque converter is different from normal ones in that there are 2 hubs, 1 inside another, to engage onto the 2 input shafts (regular and the overdrive/lockup) on the AOD. Ensure you seat that torque converter exactly right on those shafts when you install.

[CraigS]

I just looked up gear ratios for an AOD and found that 1st is 2.40-1. Wow, that is like starting a T-5 in 2nd. I don't have any TC stall speed experience but thought that might be an interesting thing to know. I would tend to follow Nuke's thoughts based on the fact that you will have an oversized mustang engine in a car that weighs a 1000 lbs less.

[j.miller]

With Nuke on this....stock is what you want...converter kinda goes on like turning the tumblers on an old safe. You should be able to find a YouTube....been a while but I believe there are 3 detents as it clicks into place.

[BobCarter]

j.
Detents? Hmm. Are you saying I will feel and or hear indexing during assembly?

[rich grsc]

Isn't that a lot of gear for an automatic? I would think a 3:08 would work better?

[j.miller]

Yes Bob, Each time in lines up it slips in a little deeper.

[NukeMMC]

Yes Bob, Each time in lines up it slips in a little deeper.

Oh that just sounds wrong! ... or right :rolleyes:

[BobCarter]

Ha!
Thats funny Nuke!
LOL

Anyway, as I join the transmission to the TC I will listen for the detent clicks.

[CraigS]

To double check that it is fully installed do some careful measuring w/ a ruler. Measure rear block surface to the flex plate at the flywheel mounting holes. Stick a straight edge across the bell housing mating surface and measure to the mount points on the TC. Both measurements should be the same. Not on AODs but I have seen guys bolt up a trans and use the bolts to move the trans that last 1/8 inch to the block. They found out later that they had messed up.

[BobCarter]

Craig, thanks for your input on mounting. Also, your comment regarding center section gearing spurred me to reevaluate my gear selection. I'm limited on choices however, since on the 20th anniversary IRS I must use a 2015 GTcenter section.
Choices are- 3.31, 3.55, or 3.73. Engine RPM's at 60 mph using an AOD are:
For 3.31 1,839 RPM
For 3.55 1,972 RPM
For 3.73 2072 RPM
So... I have decided to go with the 3.31 gear.
Thanks for your opinion I think I will be must happier at the lower Engine RPM.