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Thread: Stall speed selection for AOD

  1. #1
    Member BobCarter's Avatar
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    Unhappy Stall speed selection for AOD

    Short story-
    Purchased a 351W with a Ford AOD and torque converter. After researching stall speed selection I am confused.
    Typically stall speed selection is a function of a number things, including how the car will be driven (street or track),cam power band, vehicle weight, gearing etc. etc. So here's the issue. My engine and transmission supplier provided a 2200 stall speed based on all the traditional and proper selection methods. A representative of FFR, however, has raised a big Red flag about this stall speed and said it will be difficult to bring the Roadster to a stop at a stop sign or at a traffic light. (YIPES!) This concern is based on his real life experience-"Some builders using AOD transmissions and other auto transmissions raised concerns about proper brake function. It was determined the brakes were fine. All evidence points to the stall speed being too low. The fix on these previous builds was a 3200-3500 stall speed on the torque converter."

    So, what to do?
    My concern is with a higher stall speed the slippage during normal street driving will raise the trans oil temp and even with a cooler mounted on my radiator I may be slowly killing my transmission.

    Thanks to all of you who have sent me tips before on this and other issues. I'm hoping there is someone out there who can help me make the right decision on stall speed.

  2. #2
    Gordon Levy's Avatar
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    Can, use and such make a big difference as to stall speed. Typical moderate performance street engines would want 2200-2500. The aod builds we have done we use a 2200 stall.
    As for the issues coming to a stop sign, I have to call BS. If your engine drops revs as it is supposed to when you get off the throttle it won't be a problem. If you have an engine that stays at higher revs for a period of time before it drops off, you have some serious tuning issues.
    2200-2500 stall will not produce much heat.
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    Director of R&D, FFR Jim Schenck's Avatar
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    The problem isn't the actual stall speed, it's the advertised stall speed. What is advertised is what rpm the converter stalls in a fox mustang or similar weight vehicle, but the rpm it grabs in a lighter car like a 33 or MKIV is significantly lower. We have a few 33s with automatics where we had to pull the converter back out and switch to a higher stall speed in order to have good low speed drivability, otherwise the car would be difficult to keep at parking lot speeds or even hold at a stoplight. We now recommend around an advertised 3500 rpm converter stall but in the finished car that will give closer to 2000 rpm in actual street use. All of the cars we have built using that 3200-3500 range have had excellent street manners.
    Jim Schenck
    Factory Five Racing

  4. #4
    Member BobCarter's Avatar
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    Thanks for the input guys. Looks like a 3200-3500 as FFR recommends is the way to go.

  5. #5
    Mark Dougherty's Avatar
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    Jim what brand converters are you using
    I am having the same issue on the silver cobra
    (as I slow to a stop the converter does not unlock and it drags the engine down then aggressively unlocks as I stop.)
    I was under the impression this was a TV cable adjustment and was going to work on that.
    have you tried adjusting the cable to resolve this issue?
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  6. #6
    Mark Dougherty's Avatar
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    Bob
    I have done a bunch of work in Springfield on FFR cars
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  7. #7
    Director of R&D, FFR Jim Schenck's Avatar
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    Mark,

    Not unlocking is what we thought was going on initially. We adjusted the cable numerous times but still couldn't get the car to act right at low speeds so we sent the converter back and had them remove the lockout mechanism entirely thinking that would do it for sure. We put the non-locking converter in and it still had the same issue and that was when we knew we just needed a higher stall. We have tried 3 or 4 different manufacturers and even though they are not all exactly the same they all stalled too low even when we gave them the vehicle weight for the calculation.
    Jim Schenck
    Factory Five Racing

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    Well guys this is a big issue for me. My stock 351w and aod is a pita to get stopped at the light. Tony told me a while back that I needed a higher stall converter. I finally got tired of scaring the crap out if myself and pulled the trigger on a new aod from Monster transmission complete with a 19-2200 rpm stall converter. Now I see this post saying I should use 32-3500 stall. This can be done but I am very serious when I say I only want to do this once. What are the actual impacts of using 1900vs 2300, vs 2500 stall speed in this stock environment like mine? I don't show a monster listing for a 32-3500 converter but I will ask it that's absolutely what I need. I expect this car to be drivable for my girls and not be dangerous to those novice drivers with limited experience. Please help me get this right whether it needs 1900, 2300, 2800, or whatever? Fyi, I'm using the stock for supplied brakes up front and powerstop stock rears. No fancy cam or other performance goodies at this point. Ineed your HELP JIM, TONY, MARK OR ANYONE ELSE,!

  9. #9
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    Power brakes solve all these issue, IMO. I have a 400+HP 347 with an AOD with shift kit. 2500 stall speed with lock up and zero problems. Without P/B is where you can run into stop light issues.

    3000 stall fixes that, (if you have manual brakes), IMO.

  10. #10
    Seasoned Citizen NAZ's Avatar
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    Bob, I don't see where running a looser converter up to 3500 RPM is going to add a significant amount of heat that can't be easily dealt with. I run a 5000 RPM stall convertor on the street with a Powerglide and use a stand alone oil to air cooler mounted in about the worst location for airflow and no fan or scoop -- no problem overheating. You have some suggestions from folks with real world experience that sounds reasonable. Most of the high performance convertor manufacturers will custom make a convertor with the stall speed you need. I run Hughes Performance converters in my race car and they work great. The guys at Hughes are easy to work with so if you get stuck, give them a call.

    Also, stall speed is more a concept than an absolute speed so don't fret if you order one for 3000 and it stalls at 2800 or 3200. Mine stalls at 4500 in 8000' DA and 5100 in 1000' DA and that is to be expected as up here in Flag an engine doesn't make near as much torque as down in PHX.
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  11. #11
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    Thanks for the input but I'm not in a position where I can go with power brakes. I looked at Whitney solution but it was not right for me. I can't get past the fact that a car that weighs less than 3k lbs would need power disk brakes to make it stop. If in fact the problem is the stall speed then Factory Five Racing needs to step up and say so when people buy their kits. They asked me what engine/trans combo I was using but never mentioned a 3k stall converter would be necessary to make their product safe to drive. That's irresponsible on their part. I'm going with a 3k stall unit but I am very unhappy that I had to do this after the fact on a finished car. How simple it would be to tell the customer he needs a 3k converter when the kit is ordered. Why does FFR just ignore the problem that has first been documented in this thread since 2016 and continue to put it's customers at risk of blowing through the first stop sign they meet? Hopefully, newbies will read this posting if they intend to use an aod transmission, buy a 3k converter up front and be very happy customers in the end. God help the ones who don't stumble onto this info.

  12. #12
    Senior Member FF33rod's Avatar
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    Doesn't the Roadster build manual spell this out? The reason I ask is that in the manual for the 33 hot rod the recommended stall speed is clearly spelled out
    Gen 1 '33 Hot Rod #1104
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    My ride is the 33. The revision of manual I got was Rev D. It contained no mention of 3500 stall requirement at that revision. Unfortunately, FFR fails to routinely notify it's customers of updates to its manuals allowing them, the customer, the opportunity to apply the changes if needed on their kit. The fact that I spent countless hours struggling with poor braking performance as can be attested by Mark Dougherty from the many call I made to him, would have been eliminated had FFR put this info out there in 2016 or earlier when they found it to be true. I had one brief mention by Tony that he had problems with his personal car running an aod and he had improved it by going to higher speed converter. That was after Jim Schenck posted his findings in late 2016. I don't know when the manual update was made and I don't care. I will go with the "required" stall converter and hope for the best. Sorry it took this much time for the info to reach me.
    Maybe the moderator can move this to the 33 forum and help some of those guys.

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    Senior Member FF33rod's Avatar
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    In that case, thanks to folks like yourself who find these problems and make them obvious so the manual eventually gets updated, mine is version V2 (not to be confused with gen 2).
    Gen 1 '33 Hot Rod #1104
    347 with Holley Sniper & Hyperspark, TKO600, hydraulic clutch, IRS, Foose 18" Wheels, 245 & 315 BF Goodrich G-Force Rival S tires, DRL, power windows, roadster & hard top, Digital Guard Dog keyless Ignition

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    Reread my book. It's actually Rev 2d October 2015 kit is 882 delivery date 2/14/2016 even my digital manual was Rev 2d. Good luck.

  17. #16
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    3500 stall speed really stinks in this car!

    Following up on the Stall speed issue. I have my bpe 347 fuelie now installed along with my rebuilt aod and a 3500 rpm stall converter from Roadrunner Converters. I am very disappointed in the drivability of this combination and blame it on the high stall speed. From a full stop I need to get over 2000 rpm to start moving. The motor and trans seem to work well together once moving but every stop/start is a pain. I am now faced with a car that's no fun or the job of replacing the converter which sux!. I would suggest that newbies going the AOD route stick with the a stall speed of that 2200-2500 range. I have no idea how Jim Schenck got their 33s to have "excellent street manners" with a 3500 stall but I know what I don't like and I don't like this setup. Good luck.

  18. #17
    Director of R&D, FFR Jim Schenck's Avatar
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    I think your problem is more likely that different manufacturers can list stall speed differently, the converters we have used from Monster and others (have not used Roadrunner) have been for both the AOD and 4R70W in a good number of cars and have been very street friendly at a mid 3000s stall speed. If you get a converter that you like in a certain stall from a certain brand and recommend it then that is great info to share, but I would try it first as it may not do what you expect, particularly if its from a different manufacturer than your last one.
    Jim Schenck
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    I found the same problem in my '33 with a Coyote, it was hard to hold at a stop light and driving into my shop on a painted floor was downright scary. I changed to the converter recommended by FFR (3200 rpm stall)and I can now drive without a big leg on the brake pedal. I have an AODE 4R70W with Power Train Control Solutions Electronics built by Performance Automatic.

  20. #19
    Seasoned Citizen NAZ's Avatar
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    Just a reference point. I have a 6000 RPM stall speed converter in my SBC powered 33HR with a Powerglide 1.80:1 ratio 1st gear and 3.90:1 rear on 28" tires. The car weighs <2500lbs with me in it and full of fuel and will start to move at idle on flat ground (idles at 1000 RPM in gear) when I take my foot off the brake. 1100 RPM in 1st moves the car @ 10-15 MPH, ~2200 RPM @ 45 MPH, and ~3200 @ 65 MPH.
    33 Hot Rod Super Pro Drag Racer
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    Quote Originally Posted by NAZ View Post
    Just a reference point. I have a 6000 RPM stall speed converter in my SBC powered 33HR with a Powerglide 1.80:1 ratio 1st gear and 3.90:1 rear on 28" tires. The car weighs <2500lbs with me in it and full of fuel and will start to move at idle on flat ground (idles at 1000 RPM in gear) when I take my foot off the brake. 1100 RPM in 1st moves the car @ 10-15 MPH, ~2200 RPM @ 45 MPH, and ~3200 @ 65 MPH.
    What are you suggesting, NAZ? You think Stall is not the problem?

  22. #21
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    Quote Originally Posted by Jim Schenck View Post
    I think your problem is more likely that different manufacturers can list stall speed differently, the converters we have used from Monster and others (have not used Roadrunner) have been for both the AOD and 4R70W in a good number of cars and have been very street friendly at a mid 3000s stall speed. If you get a converter that you like in a certain stall from a certain brand and recommend it then that is great info to share, but I would try it first as it may not do what you expect, particularly if its from a different manufacturer than your last one.
    You are absolutely right about that. Wish it was a little simpler to swap converters on these hotrod but that's looking like my only option after I have my transmission shop check it out. Btw, the roadrunner recommendation came from my buddy, Tony Z.

  23. #22
    Seasoned Citizen NAZ's Avatar
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    If the stall speed is a problem for your drive-ability then it's a problem, I'm not second guessing you. I'm simply puzzled why yours is taking so much engine speed to get it moving. Of course that RPM will depended on how much throttle you apply from a stop, give it a hit at WOT and you'll see it hit the stall speed in a heartbeat. But I wouldn't have expected a slow roll into the throttle would get the revs up to 2000 plus just to get the car moving. That would be annoying for a street car.

    My new converter doesn't really act much different on the street than my old 5000 RPM stall speed converter which also surprised me. But I provided some performance details on mine only as a reference knowing that your converter should not take near as much RPMs to get the car moving.

    Have you stomped on the throttle to see what stall speed you're actually getting? Perhaps it's much higher than what it was advertised at. Regardless, it won't heal itself so if it's not what you wanted the unfortunate reality is it needs to come out and get the stall speed modified to fit your needs. I just went through this myself when I pulled my converter and sent it back to Hughes Performance to have them remove the sprag and increase the stall speed. PITA, but the only way to get the converter working like I needed.
    33 Hot Rod Super Pro Drag Racer
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  24. #23
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    Thanks for the vote of confidence. Yep, I held brakes on and stomped it. Went to approx 25-2800rpm before rears lit up. Stock brakes even with power won't lock up those tires under this motors grunt. Yeah I know I probably need to change it back out. So looms like a good winters weekend project, hell, at least I can give my kids a good idea what I want for Christmas. .. take care.

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    Have you put many actual miles on it yet, or just the initial test drive? I ask because the first time I installed a custom convertor on my fox body , the first time I went around the block I thought the same thing...it's too loose, this ain't gonna work. Went in, called the builder and told him it was too loose. This was also my first experience with a higher stall convertor. Anyways, he said try it for a week or two and get used to it, but if I still didn't like it he would fix it. He was absolutely right. After a week of driving the car, I got used to the difference and it felt completely normal and ran great.

  26. #25
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    You have a great point. I have about 20 miles or so since I installed the converter. It is fair to also note that the transmission was rebuilt by a shop and the motor is new to me as well. At this point my direction is to have the transmission shop check it's work before I make any decisions. Only then does it make sense to replace the converter. Sread, thank you for your suggestion. Once I have sign off that the transmission is functioning properly I will certainly put on a lot of miles before proceeding.

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