4l60e hits rev limter before shifts
03-07-2008, 04:32 PM
#1
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4l60e hits rev limter before shifts Have a 98 Z-28 with 4l60e it has been built back with stock clutches and band. ever since it was buit the firstime it has seemed to me that shifted slower.it has lessthan 500 miles since built but it will hit the rev limter before it shifts 1-2 2-3 just a couple times on motor but if you spray the car it will almost stay on limter to u lift i was told their was a switch on the valve body that takes the signal from the computer and actually tells the tranny to shift has any one had this problem or have any ideas all ready tried lowering shift points and raiseing line pressure.
03-07-2008, 04:42 PM
#2
If this is on both 1-2 and 2-3 and you have lowered the shift ponts, I would suspect theres and issue with the build.Now wile this may not be your issue we have a and issue last year with one that was doing a similar thing and the Holes feeding the shift solenoids were to large cause a no WOT up shift. Another possibiliy since you said the shifts feel soft and assuming you still have the stock stall converter would be the line presure is low and the band and 3-4 frictions just are not able to hold at WOT. But unless you have changed the rear end or converter I would think it unlikley you have a tuning issue, Do you have and SES (check engine light ) on any possible stored codes?
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03-07-2008, 05:39 PM
#7
many timeswhen using a high stall it is nessesary to alter the shift points and MPH settings to avoid a conditions some call stall wall , Bouncing the limiter, I am not a tuner by trade so I cannot advise you on how everything should be set but I am sure they can help you in the tuning sections
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03-07-2008, 06:00 PM
#11
We have found that a faulty Vehicle Speed Sensor can and will cause a transmission to not hit it's shift points.... but not be recognized as a faulty component by the PCM.
It takes a very keen eye to catch it on a scanner. The easiest way to find it is through data logging. Which is what I recommend for your car... or any car that has a suspected Tuning issue.
Only by recording when the Shift was Commanded (RPM x VSS) vs. the Time it took to execute the shift will one know that the transmission is sound. We like to see a .15 sec - .25 sec shift execution time at WOT in one of our built units.
I suspect it is a Tuning issue in the OP's case because ordinarilly we do not see issues with the 1-2 shift in a 4L60E. Also, for it to be related to both the 1-2 and the 2-3 shifts it would have to be something they have in common, like the Line Pressure... and if were the Line Pressure I would think that it would have damaged the soft parts already.
One other thing... Is it full of fluid?
Is you Tuner a Professional or a local guy with HP Tuners?
Don't spray on your unit or let it hang around the RPM limiter much at all until you determine the cause... serious damage to the soft parts can and will occur!
Hope that helps!
g
It takes a very keen eye to catch it on a scanner. The easiest way to find it is through data logging. Which is what I recommend for your car... or any car that has a suspected Tuning issue.
Only by recording when the Shift was Commanded (RPM x VSS) vs. the Time it took to execute the shift will one know that the transmission is sound. We like to see a .15 sec - .25 sec shift execution time at WOT in one of our built units.
I suspect it is a Tuning issue in the OP's case because ordinarilly we do not see issues with the 1-2 shift in a 4L60E. Also, for it to be related to both the 1-2 and the 2-3 shifts it would have to be something they have in common, like the Line Pressure... and if were the Line Pressure I would think that it would have damaged the soft parts already.
One other thing... Is it full of fluid?
Is you Tuner a Professional or a local guy with HP Tuners?
Don't spray on your unit or let it hang around the RPM limiter much at all until you determine the cause... serious damage to the soft parts can and will occur!
Hope that helps!
g
03-07-2008, 06:39 PM
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I honestly dont think its not the tune have faith in my guy he is a pro. will tell you a littel bout tanny came out my 02 was a 29 k tranny broke the ten bolt off the line in return it bust sprag destroyed clutchs local guy rebuilt got it back car was stock then no tune it seemed a littel slow shifting but did ok. was not long tranny would just seem like it would go to nuetrual then go back to working change fluid did fine couple days later "bamn" busted another sprag smoked clutches and band. told him just put it back stock got it back when i put it in also put headers no cats took it to track with bump limter 1-2 just a littel thought it was cause of new headers got it tuned did'nt matter spray it want change to you lift.
03-07-2008, 07:27 PM
#13
Ok, that tells me alot.
I would suggest then that the issue is indeed inside the unit. It is possible that the pump slider is binding not allowing pressure rise. It is possible the 1-2 and 2-3 shift issues are not related at all. Meaning, the 3-4 clutches can have excessive clearance and the 1-2 circuit could have an issue like a sticking valve, a crossleak or evan a leaky accumulator.
Why don't you give me a call tomorrow, I'll give you some advice on how to proceed and some options to work with.
g
I would suggest then that the issue is indeed inside the unit. It is possible that the pump slider is binding not allowing pressure rise. It is possible the 1-2 and 2-3 shift issues are not related at all. Meaning, the 3-4 clutches can have excessive clearance and the 1-2 circuit could have an issue like a sticking valve, a crossleak or evan a leaky accumulator.
Why don't you give me a call tomorrow, I'll give you some advice on how to proceed and some options to work with.
g
03-07-2008, 09:21 PM
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In order to fix this problem. You need to go into the tuning program-
take the old gear ratio divide by the new one. then you get a decimal number. Take that number and scale it into all of the transmission shift tables and the torque converter lock up tables...
I use tunercats, and thats how i do it and has worked for me the 3 times ive changed gears..- obviously there is still some fine tuning on it, but it should get you close. Also, raise your rev limiters to like 6000 or so but it should shift w/o bouncing after you scale them.
If you have any questions on adjusting the tune, get ahold of Vince at Trifecta Performance..
take the old gear ratio divide by the new one. then you get a decimal number. Take that number and scale it into all of the transmission shift tables and the torque converter lock up tables...
I use tunercats, and thats how i do it and has worked for me the 3 times ive changed gears..- obviously there is still some fine tuning on it, but it should get you close. Also, raise your rev limiters to like 6000 or so but it should shift w/o bouncing after you scale them.
If you have any questions on adjusting the tune, get ahold of Vince at Trifecta Performance..
