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Thread: can high stall TC cause transmission damage?

  1. #1
    Garrett booster
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    can high stall TC cause transmission damage?

    I have (should say HAD) a fully built transmission. Has all the goodies that are listed in the knowledge center and until recently has performed perfect. Over winter I purchased a high stall TC and got it installed this spring. It was supposed to be rated around 4200 rpms. I had a difficult time installing the TC, but eventually got it lined up and fully installed. Once trans was in I started the van up and the transmission was making a loud howling noise. After a few test runs around the block the trans sprung a leak from the input shaft seal. Took it to the trans shop that built my trans, they replaced the seal and rebuilt my trans pump. I requested they keep labor costs to a minimum so they didn't dig through the trans more than a visual inspection with trans pump out and pan off. But said fluid looked good, and internals looked good from what they can see.

    Fast forward to last weekend, finally get a chance to get van ready for a track day. I'm working on the 2 step and trying to get my big --- turbo to spool. I was doing a brake torque, had the RPM's up to around 4800 rpms, had about 10 psi and I heard a snap. Engine free revved and I quickly shut the engine down. I get out and find fluid pouring from the cover for the transfer gears. I have not dug into the trans at all, so not sure what exactly happened, but thats not my main concern right now, just sharing for a little background info.

    What is everyone's opinion on the TC? Could the high RPM's have caused something to break internally? is this TC cursed? I've purchased another turbo, a smaller one, which should be much easier to spool. I have a spare transmission that has been built, but I have no idea what the specs are on the build. I'm going to put the spare trans in the van, but don't want to use the high stall if it's going to cause more problems. At the same time, I'm not sure if a stock torque converter will be able to allow the motor to build boost for a launch even with the smaller turbo.

    Look forward to hearing everyone's thoughts.

  2. #2
    Garrett booster
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    Re: can high stall TC cause transmission damage?

    Simple answer is yes.

    The torque converter multiplies torque. The higher stall allows you to get to a rpm where you're making max engine torque and multiplying that by around a 2-2.5:1 ratio. A typical turbododge can produce 400ft/lb pretty easily. Multiply that by just 2:1 on the low side, then throw in your 1st gear ratio and you're well over 1000ft/lbs at the transfer gears, even before transfer gear ratio or final drive ratio comes into play.

    The original problem could have just been your install, or depending on converter design and the way it was built, it could be catching on the input seal from converter thickness and/or the converter input weld being too proud and not being machined down, like mine was in the past.

    What's the info on the rest of the build?

  3. #3
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: can high stall TC cause transmission damage?

    Joe, are you using a 2-step?
    Mike Marra
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  4. #4
    Garrett booster
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    Re: can high stall TC cause transmission damage?

    A the time I broke the trans I was NOT using the two step. I wanted to see how much boost I could build while holding it back with the brakes. On 2 step at 4200 I was only getting 5-7 psi.

    As for whats the rest of the build, I'll have to type that response put at home on the computer. To much to do on my phone while working.

  5. #5
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by Joe_Van_Duno View Post
    A the time I broke the trans I was NOT using the two step. I wanted to see how much boost I could build while holding it back with the brakes. On 2 step at 4200 I was only getting 5-7 psi.

    As for whats the rest of the build, I'll have to type that response put at home on the computer. To much to do on my phone while working.
    I broke two trans cases while holding the brakes against the converter and trying to build boost. In the end, I gave up trying to do that and left with very little boost and sprayed it right out of the hole to get the turbo spooled. Not sure if by doing that I gave up any 60ft, but the trans lived.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

  6. #6
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by Joe_Van_Duno View Post
    A the time I broke the trans I was NOT using the two step. I wanted to see how much boost I could build while holding it back with the brakes. On 2 step at 4200 I was only getting 5-7 psi.

    As for whats the rest of the build, I'll have to type that response put at home on the computer. To much to do on my phone while working.
    I broke two trans cases while holding the brakes against the converter and trying to build boost. In the end, I gave up trying to do that and left with very little boost and sprayed it right out of the hole to get the turbo spooled. Not sure if by doing that I gave up any 60ft, but the trans lived.
    With the new setup, I stayed with a smaller turbine to get it to spool easier, and with the megasquirt, I can bring up the RPM against the converter, and the 2 step will kill some torque to reduce the strain... in theory.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

  7. #7
    Garrett booster
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    Re: can high stall TC cause transmission damage?

    Ok, so what I'm hearing is...

    A) go with smaller turbo
    B) should be able to get away with higher stall if I keep the 2 step active and below a certain RPM. Maybe say 4000?
    C) if boost is still low....well, I do what I always do.... Spray the -----!!!

  8. #8

    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by contraption22 View Post
    I broke two trans cases while holding the brakes against the converter and trying to build boost. In the end, I gave up trying to do that and left with very little boost and sprayed it right out of the hole to get the turbo spooled. Not sure if by doing that I gave up any 60ft, but the trans lived.
    With the new setup, I stayed with a smaller turbine to get it to spool easier, and with the megasquirt, I can bring up the RPM against the converter, and the 2 step will kill some torque to reduce the strain... in theory.
    Hey Mike, where did the two cases break when you were braking against the converter?
    best 1/8 ET-6.16 sec. best 1/8 speed-119.70 Best 1/4 MPH 145.5, Best 1/4 ET 9.65 sec. 8 valve NO NITROUS!!

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    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by Warren Stramer View Post
    Hey Mike, where did the two cases break when you were braking against the converter?
    x2
    I got a dog in this fight also...
    Wayne H.

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  10. #10
    boostaholic
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    Re: can high stall TC cause transmission damage?

    I have always ran small enough Turbo to just barely bring above idle and grab the bottle, best 60 foot times this way...

  11. #11
    Supporting Member Turbo Mopar Contributor rdnoel86's Avatar
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by Joe_Van_Duno View Post
    A the time I broke the trans I was NOT using the two step. I wanted to see how much boost I could build while holding it back with the brakes. On 2 step at 4200 I was only getting 5-7 psi.

    As for whats the rest of the build, I'll have to type that response put at home on the computer. To much to do on my phone while working.

    Some of the big hp guys (900+) leave on around 8lbs of boost and hit it with a 50 shot of nos. If you watch some of Stephane's video's he come of the line easy then nailed it....

  12. #12
    Supporting Member Turbo Mopar Contributor rdnoel86's Avatar
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    Re: can high stall TC cause transmission damage?

    BTW I'd be interested to know what broke...

  13. #13
    Garrett booster
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by rdnoel86 View Post
    BTW I'd be interested to know what broke...
    Yeah me too!! Not sure if I'll figure it out this weekend, I'm hoping to at least swapnout the trans with my spare.

    So ido the big hp guys even bother using high stall? or Do they high stall just set the two step lower and spray as soon as my foots off the brake.

  14. #14
    Supporting Member Turbo Mopar Contributor rdnoel86's Avatar
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by Joe_Van_Duno View Post
    Yeah me too!! Not sure if I'll figure it out this weekend, I'm hoping to at least swapnout the trans with my spare.

    So ido the big hp guys even bother using high stall? or Do they high stall just set the two step lower and spray as soon as my foots off the brake.

    Yes...

  15. #15
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: can high stall TC cause transmission damage?

    Quote Originally Posted by Warren Stramer View Post
    Hey Mike, where did the two cases break when you were braking against the converter?
    I'll dig around for the pictures.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
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  16. #16
    turbo addict Turbo Mopar Contributor
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    Re: can high stall TC cause transmission damage?

    Even if you have a high stall, you shouldn't give her all the beans. Its been known forever that will kill the transmission if it doesn't pull through the brakes.
    Its perfectly all right to do the 2 step, and if you don't have enough boost, you should tune you 2 step differently. Pull more timing, cut cylinders. Dump fuel. IMO, a 5000 rpm stall situation should not be bogging even if you don't have much boost.
    You don't see anybody fast who makes passes leaving hard AWD or FWD. Anyone who likes to go rounds hits soft, even when they are setting records. That is what I have always seen. The guys throwing caution to the wind are never the ones setting serious records. Those are the customers throwing cash till its gone.
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  17. #17
    Garrett booster
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    Re: can high stall TC cause transmission damage?




    Well as some had suspected I damaged my transfer gears. And based on the angle the lower gear is at, I'm guessing a shaft of some sort snapped also. I'm not a transmission guy at all, so I won't be disassembling any further, but when my trans shop takes a look at it I'll ask for pictures.


    Yesterday I was pretty productive and was able to install my spare transmission and remove my turbo. I plan on running a different turbo, keeping the same high stall converter, just doing as people have suggested and keeping the 2 step active and below 4000 rpms. I'll keep playing with the settings on the 2 step and hope to build boost off.
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  18. #18
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: can high stall TC cause transmission damage?

    That worries me.
    Wayne H.

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  19. #19
    Supporting Member Turbo Mopar Contributor rdnoel86's Avatar
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    Re: can high stall TC cause transmission damage?

    I know where you can get some billet transfer gears.....

    Also, this won't help you any, but weight is a huge enemy of these trans's......I know having a van there isn't much you can do about it...

  20. #20
    Garrett booster
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    Re: can high stall TC cause transmission damage?

    Looks like the pinion shaft broke or the part of the case that holds the pinion bearing retainer on the other side broke and let the gears spread causing the stripping of the teeth. That piece behind the lower gear that you can see sticking out is the governor carrier. Is houses one of the bearing races for the pinion shaft and the governor housing. It's not bolted down so when the shaft breaks it's able to walk out with the piece of the shaft and the bearing. I broke my pinion shaft once but it didn't hurt the transfer gears. Did you try to pull on the lower gear to see if it would come out with a busted piece of pinion shaft? If it won't come out that would point towards a broken case. You should be able to see what's going on if you remove the oil pan.

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