Help selecting a torque converter AOD & 351

[mattt]

I know very little about torque converters and it is one of the last things I need to get before dropping the new combo into place. How about some recommendations on what to use? Or, what is the way to choose stall speed, mfg, etc.

 

[FASTERDAMITT]

I would not buy an off the shelf converter. Some are tight and some are loose depending on the vehicle weight, gears, tire size and torque. Have a race tranny builder set up one the way you want to drive it. They usually will make a change if you prefer it to be looser or tighter. Mine is sold by Lentech Transmissions and is a 2200 stall 12" converter. Works great with my setup. If I was not driving on the street as much and wanting economy I might have had it set up looser for quicker acceleration.

 

[rjlougee]

The best thing you can do is talk to a reputable builder.

The guy who built (always builds my auto trannys) my AOD recommended one based on driving conditions, the engine (408), etc... IIRC it has a SP41. I'd have to check the box to make sure that's correct.
Joe

 

[mattt]

I'll have to check with some local builders then. I bought the trans already built/rebuilt with adapter installed and the engine is just about together. How much of TC selection depends on the engine power band? Reason I ask is the 351 is getting some special treatment(non stock). Alum. heads, TFS-1 roller cam, roller rockers, Lightning GT40 upper and lower.

If I had the trans built by someone, I could defer to them, but I bought it ready to go in.....so I haven't worked with anyone.
Thanks for the suggestions guys.

 

[FASTERDAMITT]

The TC builder will ask about the build of the engine if they are going to do thier best for you. If you used a local tranny shop, I would call a race shop to get the best converter for your pkg. In my history, I have been most happy with converters and trannys from Performance Automatic. Here's thier website: http://www.performanceautomatic.com/converters.htm

 

[mattt]

I checked with two local trans, TC shops. One is TCS out of Chino, CA....they build torque converters, and are players in the off road race crowd here in Socal. They recommended one of their AOD-15A units. Roughly 2200 stall, and I think he mentioned it is built internally to tie two of the 3 step input shaft together. Under $200....I was surprised so inexpensive.

I also spoke to Art Carr at his shop in HB, CA. He said he would build one for just over $300....2400 stall. He was asking if the trans I have was built "lock up?" I didn't know, as I bought the trans already built and converted.

The input shaft of the trans I have is a 3 step splined shaft. Hopefully I can find the info I got about the trans from the previous owner. One other thing I'm not sure about is if engine imbalance comes into play with the TC. The flex plate is a stock 94 351W Lightning piece. I'd guess the AOD I have was at some point in it's past behind a 302, which could be the 50oz imbalance vs. the 351 28oz. Is this something that needs to be figured out so everything matches up together?

 

[ken75ranger]

The imbalance is all in the flexplate. As long as the flexplate has the same bolt pattern as the converter you're good.
I use http://www.edgeracingconverters.com/ in Simi Valley for my conveters. They aren't too far from LA if you want to check our another shop.

 

[mattt]

Just about ready to pull the trigger on this......I'm looking for one more round of opinions. Lock up or non lock up converter?

I'm being told if I go lock up that with the AOD and how it's geared[stock], that it will be a total dog to drive once it gets up to 3-4 gear. Anyone who's BTDT...lock up or non lock up?

 

[FASTERDAMITT]

I had lockup at first, yes it sucks and feels doggy! I now have non lockup and I use a Lentech valvebody switchable overdrive lockout that eliminates the shift to OD when wanted. If you do not have this I would go non lockup. Now that I have this VB I may go back to lockup.
FYI, I have a spare VB that has the epoxy OD mod done if you are interested. It will only go into OD only if you back off the throttle momentarily to let it shift. I can tell you more if interested.
I only used it for a spare when i was having my Lentech VB modified to my new gears. (took 3 weeks!)

 

[mattt]

Looks like it's non lock up then. Thanks. I've been wondering about many issues that you just brought up. I'm going to run a Winters gate shifter which I've been told the gate pattern is P R N D 2 1. What I've been wondering is how to manually select 3rd and keep it out of OD if need be. It sounds like the VB you have allows that option. Is the VB you mentioned selling a modified factory VB or it is Lentech also? I'm probably interested in it. How much for it? I've heard many good things about Lentech components, but haven't done the research on any of them yet. With your Lentech setup, do you have a switch or something to lock out OD?

I'm guessing I have a stock VB in my AOD since there was no mention of an aftermarket VB when I bought this trans already built. I was told it should have the following.....
clutch kit 7 frictions (versus the factory 5) this increases holding power by 40%
2" wide OD band with mechanical diode and the A servo was changed to accomodate the od band diode
reverser drum spiral ring
Boost valve kit
Bushings
Reprogramming kit & Master rebuild kit

ArtCarr told me to "shuffle shift" it to hit 3rd and not OD. I called ArtCarr because they apparently have a gate plate and hardware/shifter arm kit to make my Winters shifter work with an AOD. Winters does not offer anything for the AOD, they only have components for AOD-E.

 

[Broncobowsher]

Actually I would look at the lock up.
If the cruising RPM isn't above the stall speed then the convertor will experience excessive slip in overdrive. All this will do is burn a bunch more gas and put all that extra heat into the transmission. Especially true if running a higher stall converter.

The AOD run a unique design for lockup. There is a 3rd shaft that delivers direct engine power (bypassing the converter) to the rear of the transmission. (third gear is wierd, I will get to that at the end) but 4th gear, the overdrive, completely bypasses the converter. So you can idle down the highway at less then stall speed and not generate any heat in the converter due to slip. The non-lockup convertors work great in mustangs that are geared deep enough and are light enough that not being locked up in overdrive doesn't matter. Without the lockup the can slip a bit on hills and pull grades in overdrive without downshifting. Keep in mind this is a light aerodynamic car and not a heavy side of a barn. Mustang with 4.10 gears is a lot of gear, but a short tire. 4.10 gears are decent highway gears in a tall tired Bronco without an overdrive.

So if you would like the trans to stay cool and the engine to turn a fairly low highway RPM efficently, use the lockup converter.

Oh, the oddity of 3rd gear. 60% locked up and 40% not locked. How? Well direct gear happens when 2 parts of a planetary set are locked together. Basicly jams everything into a giant rotating mass and no gears are turning. Ford got fancy. instead of locking 2 elements of the planetary system together and onto the input shaft it locked one onto the input from the convertor (40% slip) and the other element onto the converter bypass shaft (60% lockup). This removes more then half the load from the converter but still gives a little multiplying under heavy load. The gearset rotates slowly at the speed difference between 2 different inputs. Racers don't like this as it bogs the engine down when they hit 3rd. So a non-lockup gives the converter slip to keep the engine in the powerband during drag races. Screw effiency, just worry about the quarter mile is the general mentality of many race shops. be careful of what you ask for, you may be getting race parts that are not happy on the streets.

 

[needabronco]

I also vote to stay with a lockup converter unless your input shaft is a solid piece. You have the '3' piece input shaft if you can pull the 'middle' or longest shaft out and the rest stays in the transmission. There are advantages to the non lockup converter if you never drive on the highway.

As far as valve body's go I have a Hughes performance VB in mine, but I bought mine used like you so I don't know how it shifts either. If I'm not happy with mine, I plan to go with a Silver Fox VB with a 4R70W overdrive servo so you can electronically switch off OD. The Silverfox VB can be customized to shift however you want it to, and he will correct the shift curve if you have the 4R70W (lowgearset) installed, the last time I looked his valve body's were under $250 shipped to your door also. I also have an Art Carr gated shifter and if I go this route, I'll install a toggle switch to lock out overdrive.

I'm going to run mine for a while before I change anything to see how I like the Hughes valvebody first.

 

[mattt]

Hmmm.....yours are the first two recommendations for lock up. I am looking for it all, good highway manners & not a dog when driving outside of OD. I do have the 3 step input shaft. A few trans builders I spoke to mentioned getting rid of the 3 piece input if the trans wasn't already built. I think it was TCS that mentioned building the converter where it will tie 2 of the three input shafts together inside the converter...but I can't remember if he was talking lock up on non lock up.

With everyone I've spoken to that sells torque converters, a 2000-2200 stall keeps coming up as the "magic number." I am aware of the additional heat generation with the non lock up, but I figured it could be handled by a good cooler. Looks like I need to do some additional research. Thanks to everyone who has weighed in on this thread, I really appreciate the tech info as I'm in the learing curve.

 

[av bronco]

I have a Edge converter and asked for 2400, its at 3000, the more power you have the higher your stall will be, no matter what stall they tell you.

 

[mattt]

So, I ordered a converter today from TCS in Chino, CA. From memory here.....12" HD Converter, 2000 stall, and a custom input inside the torque converter that will lock the smallest splined shaft and the middle shaft together inside the converter, since I have the stock 3 stage input shaft. I was driving when I placed the order so I couldn't focus on wrapping my brain around how this torque converter works, but TCS says it should fit the bill for me. TCS asked about intended usage, HP, tire size, gear ratio
I'm planning to use the Bronco 50% on road, 50% off. Engine should be somewhere in the mid 300hp range, with 33" tires.

Any opinions or experience with this style converter that locks the two smallest input splined shafts together? TIA

 

[mattt]

Something else to figure out is if I have the correct flex plate for this combo. The guy at TCS thought it should be correct, but told me to check with S. Culhane. He said all Ford AOD, AODE, & E4OD have an 11 1/2" bolt pattern for flex plate/torque converter. My existing flexplate originally was mated to an E4OD in a '94 Lightning.