broken sprag? loosing overdrive? ** come flex that tranny knoledge**
03-31-2006, 02:14 AM
#1
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broken sprag? loosing overdrive? ** come flex that tranny knoledge** ok my buddys 2000 stock t\a had this problem where if he is crusing along in overdrive and he decides to go wot the tranny intially unlocks the converter and the rpms go up a bit but then it hangs for about 1 seccond and then it seems like its slipping as its tring to perform a 4-2 shift during the slipping time the tranny hangs in the 4-5k rpm range and it sound like a munual car does when you burn the clutch
also when you put the selector in 3rd he no longer has this problem
and if you run the car form a dig it runs fine
wouldent this be the sprag slipping as its tring to hand over overdrive to 3rd ?
he rarely drives the car but as of now theres no dtc's ive tried modifying shift pressure amougst other items but they dont seem to help.. finally today he installed a yank converter and now the problem seems to be apllifed
any clues?
also when you put the selector in 3rd he no longer has this problem
and if you run the car form a dig it runs fine
wouldent this be the sprag slipping as its tring to hand over overdrive to 3rd ?
he rarely drives the car but as of now theres no dtc's ive tried modifying shift pressure amougst other items but they dont seem to help.. finally today he installed a yank converter and now the problem seems to be apllifed
any clues?
04-01-2006, 04:26 PM
#5
forward sprag is holding in 1-3. the only difference in 3rd and 4th is the band is on in 4th and the forward sprag is overrunning. sounds like a forward sprag to me. if fact that is the way that you should test sprags is to get into a gear wear it overruns like 4th and stomp on it to see what the downshift is like.
04-01-2006, 05:27 PM
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kinda didnt understand the last responce on how to test the sprag issue but basically when it is 4th and i go wot the converter unlocks then it begind to down shift but starts slipping
but when i throw it and 3rd and go wot it downshifts fine....
but when i throw it and 3rd and go wot it downshifts fine....
04-01-2006, 08:00 PM
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Hook up your HPTuners and log this action, all the tranny
slip PIDs and shaft speeds, TCC duty and force motor
current and current gear as well as MPH, RPM, TPS and
so on. From these you can determine where the slip comes
in.
slip PIDs and shaft speeds, TCC duty and force motor
current and current gear as well as MPH, RPM, TPS and
so on. From these you can determine where the slip comes
in.
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04-02-2006, 01:36 AM
#8
to simplify my post about the sprag test. your problem happens when you are in 4th and it tries to downshift. on the 4-3 downshift the band comes off and the forward sprag stops overrunning and should start holding. if it doesn't hold it will cause a problem like that you decribe.
04-02-2006, 08:17 AM
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The sprag is on only in the "1", "2", "3" position. If you are in overdrive and the transmission is making a "forced" downshift (lever still in the "OD" position), then the sprag "does not" engage, only the band comes off if you are making a forced 4-3 downshift, nothing else. If you grab the lever and go back to "3" position, then the overrun clutch/sprag in coming back on, with the band releasing, & the 3-4 clutches still holding. On a 4-2 downshift, the 3-4 clutches come off, and the band still holds, but this is not always the case. The band will come off and the 3-4 clutches release, and the band tries to come back on quickly, but now the 2-4 drum is spinning and the band cannot come on fast enough in some cases, causing this problem.
04-02-2006, 08:49 AM
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SO YOUR SAYING THE BAND?
Originally Posted by Pro Built Automatics
The sprag is on only in the "1", "2", "3" position. If you are in overdrive and the transmission is making a "forced" downshift (lever still in the "OD" position), then the sprag "does not" engage, only the band comes off if you are making a forced 4-3 downshift, nothing else. If you grab the lever and go back to "3" position, then the overrun clutch/sprag in coming back on, with the band releasing, & the 3-4 clutches still holding. On a 4-2 downshift, the 3-4 clutches come off, and the band still holds, but this is not always the case. The band will come off and the 3-4 clutches release, and the band tries to come back on quickly, but now the 2-4 drum is spinning and the band cannot come on fast enough in some cases, causing this problem.
04-02-2006, 09:02 AM
#11
Originally Posted by Jpr5690
SO YOUR SAYING THE BAND?
Last edited by FLT; 04-07-2006 at 09:10 PM.
04-02-2006, 09:44 AM
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JIM CAN YOU EXPLAIN FURTHER I LOGGED ALL THESE SETTINGS AND REALLY COULDENT FIGURE OUT WHAT TO LOOK FOR... SO WHAT SQUIGGLE DO I NEED TO BE WATCHING TO DETERMINE IF ITS TRUELY SLIPPING
Originally Posted by jimmyblue
Hook up your HPTuners and log this action, all the tranny
slip PIDs and shaft speeds, TCC duty and force motor
current and current gear as well as MPH, RPM, TPS and
so on. From these you can determine where the slip comes
in.
slip PIDs and shaft speeds, TCC duty and force motor
current and current gear as well as MPH, RPM, TPS and
so on. From these you can determine where the slip comes
in.
04-02-2006, 09:45 AM
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O Yea One Of The Runs Actually Produced A Burnt Clutch Smell.. Which To Me Was Funny Because I Didnt That Could Happen In A Automatic But It Was Pretty Distinct So I Know Somethng Smelled Like It Was Burning Up
04-02-2006, 09:56 AM
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btw COULD THIS BAND PROBLEM BE RELATED TO REMOVING TQ MANAGEMENT FOR LIKE 15 MILES OF DRIVEING?
I MEAN MY CAR HAS NO TQ MANAGEMENT AND 500+ HP AND IT RUNS GOOD SO I DONT SEE HOW A STOCK CAR COULD SUFFER THAT BAD BUT I FIGURED ID JUST THROW IT OUT THERE
I MEAN MY CAR HAS NO TQ MANAGEMENT AND 500+ HP AND IT RUNS GOOD SO I DONT SEE HOW A STOCK CAR COULD SUFFER THAT BAD BUT I FIGURED ID JUST THROW IT OUT THERE
04-02-2006, 10:35 AM
#16
No IMO where I work and with way we build we tell people to remove torque management. I'm no tuner I'll be the first to tell you that. But most people who tune say get it out of there. You also said you smelled burt clutch. I really think you should have that thing checked out with a scan tool. It will help you find it weather it's tune or trans.
04-03-2006, 03:36 PM
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Originally Posted by Jpr5690
JIM CAN YOU EXPLAIN FURTHER I LOGGED ALL THESE SETTINGS AND REALLY COULDENT FIGURE OUT WHAT TO LOOK FOR... SO WHAT SQUIGGLE DO I NEED TO BE WATCHING TO DETERMINE IF ITS TRUELY SLIPPING
Get the data out into Excel. Make a couple of new columns.
One would be the ratio of input/output shaft speeds. One
is the target i/o ratio, indexed by trans current gear so that
1=3.059, 2=1.625, 3=1.000 and 4=0.696. For a small snippet
it might be easier to just paste in the numbers for the gear
shown, rather than figuring out a fancy equation to do it
(my Excel skills are rudimentary). Anyway, now if you make
a scatter-plot and put both of these up against MPH or RPM
you will have two lines which -should- be the same; the one
tracking current gear is your ideal, and the one from shaft
speed data should track it as crisply as possible. Look at the
places where it steps; does it stay between the "from" and
"to" levels, or does it flare outside? Does it take more than
a few "ticks" (1/10 sec) to start moving and more than a
couple additional, to haul down (up) and settle in? If so then
the frictions are bad or the line pressure is not being provided.
Look at the force motor current before/during/after; it should
be tens or mA at WOT, to give you full line. If the shift is slow
or flares, but the current is good, then it's greasy time. But
maybe it is just the converter unlocking or slipping; see the
TCC slip and status there. You have to eliminate the things
that are working OK and get down to the freaks.
If you get me the log file in Excel and highlight the regions
that represent the misbehavior I can try and take a look.