powerglide launch in high gear

Old 07-28-2008, 11:34 AM
  #1  
hal7022
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Default powerglide launch in high gear

:?

I just rebuilt my JW powerglide and had the converter freshened up. Went to the track and had a decent test run on the throttle stop of 9.45 at 152MPH. Great!

Now the problem. Went back the pits and decided to bump up the throttle stop RPM. Disconnected the air from the dedenbear stop. Proceeded to put the car in low gear and pressed the transbrake button. started to raise the RPM in this mode with the idea of setting the stop RPM. Got to 3300 RPM and the motor bogged ( like the car shifted into high gear???). Converter stalls at 5600 RPM launch at 5000 RPM
Heard a sound like pressure leaking. No fluids leaking that we saw.

Checked linkage for tightness - OK
Checked pressures at servo - 200psi - OK
check band adjustment - OK

Still the same problem.

Said to hell with changing it and tried to make a pass. the car felt like it launched in low gear after the transbrake switch went off. then took off in high gear and shifted into high.

Looking for help/suggestions
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Old 07-28-2008, 04:37 PM
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Racefab57
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Check the last part of that last sentence ??? " took off in high then shifted into high" ???? !
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Old 07-28-2008, 06:50 PM
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hal7022
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Default powerglide launch in high gear

Here is how the playback tach read.

Revved the motor on the top bulb and launch on the bottom bulb; motor got to only 2800 RPM.

stop came on .3 seconds; RPM dropped to 1200

stop came off 2.3 s motor stayed at 1200

slowly built rpm to 6800 and shifted to high

hence launched like in high gear then shifted to high gear

Just tore down the tranny again and seeing no issues (fliud good, minimal clutch dust no chunks); good seals etc.

I think this is a sprag issue on the refreshed ATI converter
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Old 07-29-2008, 03:38 AM
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johnracer
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Sounds like a converter problem to me too....
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Old 07-29-2008, 04:53 AM
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sg1586
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What you explaining has happened to me with TCI.. Had a converter freshened and on the 3 pass the sprag broke!!! With a broken sprag you loose all of you torque ...
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Old 07-29-2008, 11:08 AM
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jmarksdragster
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A good reason to go spragless, consistency and reliability make it worth while.
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Old 07-29-2008, 11:31 AM
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hal7022
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Default powerglide launch in high gear

its on its way back to ATI. will let you know. Did a "bench check" and it seems ok but who knows under load. what about going spragless for super gas racing? any thoughts. Thanks :?
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Old 07-29-2008, 03:01 PM
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sg1586
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I personally would not go spragless unless you have a big motor in a digger where tire shake on a burn out almost always happens. That alone will brake or damage a sprag. Most sprag damage comes from not knowing how to do a proper burn out properly...
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Old 07-29-2008, 11:40 PM
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Tod74
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Originally Posted by sg1586
I personally would not go spragless unless you have a big motor in a digger where tire shake on a burn out almost always happens. That alone will brake or damage a sprag. Most sprag damage comes from not knowing how to do a proper burn out properly...
What does a guy do wrong in a burnout that damages the trans or converter? not debating just asking cause I do not know.
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Old 07-31-2008, 03:01 PM
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hal7022
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Default powerglide launch in high gear

heard back from ATI. He does not believe the converter sprag is an issue. He asked me to check the stator tube to see if it has spun. Tried air through the holes and doesn't look like anything wrong. I'm still looking for the problem. Its nothing obvious. I had him hold off on cutting the converter while I checked but now I think I'll have to sink the $195 they are charging now ( just up from $175) .

ANy other thoughts on what may be going on??? Thanks

BTW How I do a burn out....

drive through water box wetting the tires.
Don't spin them cause water splashes and may end up dripping on them
press the precord button on my playback tach.
Make sure the car is in HIGH gear
upon getting the signal pump the brake twice and press the line lock
the line lock is also linked the burnout rev limiter ( 6000 rpm) I have 5600 stall converter
Burnout until hazy and then let the car creep forward feathering the throttle and keeping the RPMat 6000
after moving 10 feet or so drop the rpm and get a nice chirp
hit he record button and pull into prestage
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