2-3 shift again
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
2-3 shift again Ls1 H/C/I, 400rwhp NA
RPM Level 5 4l60E
3600 miles on build
Yank SS 3600 stall
Been dealing with this 2-3 shift issue for some time now and it has never been right. At the strip the car shifts perfect and is very consistent on just motor. When I try to hit it with a 100hp shot it hangs and hits the rev limiter until I lift. About 500 miles ago I took the trans out and sent it back to RPM. They tore it apart and said it was fine so it must be the tune. Im not a tuning expert but have tried minor adjustments to some of my trans tables. Nothing has worked. Help Please!!!!
RPM Level 5 4l60E
3600 miles on build
Yank SS 3600 stall
Been dealing with this 2-3 shift issue for some time now and it has never been right. At the strip the car shifts perfect and is very consistent on just motor. When I try to hit it with a 100hp shot it hangs and hits the rev limiter until I lift. About 500 miles ago I took the trans out and sent it back to RPM. They tore it apart and said it was fine so it must be the tune. Im not a tuning expert but have tried minor adjustments to some of my trans tables. Nothing has worked. Help Please!!!!
TECH Junkie
Joined: Dec 2012
Posts: 3,621
Likes: 1,335
From: Iowa
I'll try to find the old thread if I can, but it might be long lost.
This is going to sound like a real stretch, but hang with me. I remember a post with similar issues on the 2-3 shift and it was also seen through the data-logger that there was also very erratic timing when it occurred. Long story short (and I know its a stretch) it turned out that the nitrous was, to a small extent, back-feeding into the maf/iat sensor and doing some whacky things. the trans uses signals from the engine side of things (more than just rpm and tps) to allow shifts and with this particular set of conditions, it just wouldn't let it into 3rd.
I'm gonna bet good money this is not your problem, but it was interesting enough for me to remember so I thought it was worth a mention.
A more likely option is to look at where your solenoids are wired. The transmission solenoids are activated by grounding them. If somehow your ground for the solenoid, or even the power side of things is interfering with this process, You'll never be able to excite that solenoid, and you'll never get into 3rd.
This is going to sound like a real stretch, but hang with me. I remember a post with similar issues on the 2-3 shift and it was also seen through the data-logger that there was also very erratic timing when it occurred. Long story short (and I know its a stretch) it turned out that the nitrous was, to a small extent, back-feeding into the maf/iat sensor and doing some whacky things. the trans uses signals from the engine side of things (more than just rpm and tps) to allow shifts and with this particular set of conditions, it just wouldn't let it into 3rd.
I'm gonna bet good money this is not your problem, but it was interesting enough for me to remember so I thought it was worth a mention.
A more likely option is to look at where your solenoids are wired. The transmission solenoids are activated by grounding them. If somehow your ground for the solenoid, or even the power side of things is interfering with this process, You'll never be able to excite that solenoid, and you'll never get into 3rd.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Appreciate the response MaroonMonster LS1. Not sure how you would figure out that your nitrous was backfeeding your maf/iat sensors. Dont think that is my issue. All of my nitrous controls are on separate system than any of my engine controls or trans controls. All connected to direct battery power and battery ground. It could be something strange but im not there yet
TECH Junkie
Joined: Dec 2012
Posts: 3,621
Likes: 1,335
From: Iowa
A quick easy check would be a voltage check across your shift solenoids. With bottle and fuel off obviously, excite the nitrous solenoids, and see what voltage across shift solenoids is.
If you have hp tuners, command the solenoids that would be activated for 2-3 shift and see if they read as they should. If you get the drop you need, good. if not, start chasing grounds.
I've attached a chart to use when you force solenoids with hp tuners.
if you put a voltmeter across the test pins on the solenoids, you should read 12v when the solenoid is ON and 0v when it is OFF
Keep us updated with what you find.
If you have hp tuners, command the solenoids that would be activated for 2-3 shift and see if they read as they should. If you get the drop you need, good. if not, start chasing grounds.
I've attached a chart to use when you force solenoids with hp tuners.
if you put a voltmeter across the test pins on the solenoids, you should read 12v when the solenoid is ON and 0v when it is OFF
Keep us updated with what you find.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Good info and something I will try to do this weekend. I assume I can access the shift solenoid pins right off the plug that goes into the tranny. Just unplug it and identify the correct pins. Is that correct or is there another way to access these pins. I have hp tuners so I do know how to activate the 2-3 shift.
TECH Junkie
Joined: Dec 2012
Posts: 3,621
Likes: 1,335
From: Iowa
This will be helpful so that you don't have to drop the pan. Little different procedure though. find the control wire for that solenoid (B in the link) and check it against ground.
Checking it this way is backwards from before because you're checking against ground. so
you should have 12V when OFF
and 0V when ON
http://www.msgpio.com/manuals/mshift/wiring.html
Checking it this way is backwards from before because you're checking against ground. so
you should have 12V when OFF
and 0V when ON
http://www.msgpio.com/manuals/mshift/wiring.html
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TECH Resident
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I would put a 0-300 psi. gauge on this and get some readings at WOT in 1st, 2nd & 3rd gears without the nitrous. The pressures should be 235 - 245 psi. Anything lower than 220 psi. and the 2-3 shift is the first shift to cause problems when the torque goes up. The port is above the manual shift lever apx. 4-5". If the pressure readings are low, disconnect the main plug wire on the passenger side of the transmission and see if the readings go higher on the 1-2 manual WOT shift, you will not be able to do a 2-3 shift with the plug disconnected. If the pressure goes up, then this is a computer and/or sensor problem causing lower pressures. If no change, then the EPC solenoid will need to be adjusted to get the right pressure. I am assuming that RPM has the back to manual low feature, otherwise it will start in 2nd gear even when in manual low with the main plug wire disconnected. Try this first to make sure the transmission is ok.
In my experience the problem is not a mechanical one , Here is what is happening, You have the shift points set without spray along with rev limiter, The problem is when you spray you increase power and torque so the rate of RPM climb is faster. So now there is not enough time from shift command to complete the shift.
You have to understand this time is a constant but when you increase power the rate at which the RPM rise is faster So where N/A you might command the shift at 6700 rpm for example and it will complete by 7000 rpm (assumed rev limit) 300 rpm allowed now you spray the RPM climb is now greater that 300 rpm due to the power increase so the shift can no longer be completed in the RPM allowed.
Options are a bit limited If your engine can handle it you could try raising the rev limit by a couple hundred RPM.
It might be ask why does second not have this issue, This is because second actually always takes less time to complete, 2nd is simply applying the band. 3rd is applying the 3/4 clutch while simultaneously releasing the band all in the same fluid circuit as the two near overlap.
Hope this helps but what it comes down to you are either going to have to lower the 2-3 shift point to compensate for the additional power or raise the rev limiter to allow for the additional RPM increase, For consistency purposes if possible raising the rev limiter is the best solution.
You have to understand this time is a constant but when you increase power the rate at which the RPM rise is faster So where N/A you might command the shift at 6700 rpm for example and it will complete by 7000 rpm (assumed rev limit) 300 rpm allowed now you spray the RPM climb is now greater that 300 rpm due to the power increase so the shift can no longer be completed in the RPM allowed.
Options are a bit limited If your engine can handle it you could try raising the rev limit by a couple hundred RPM.
It might be ask why does second not have this issue, This is because second actually always takes less time to complete, 2nd is simply applying the band. 3rd is applying the 3/4 clutch while simultaneously releasing the band all in the same fluid circuit as the two near overlap.
Hope this helps but what it comes down to you are either going to have to lower the 2-3 shift point to compensate for the additional power or raise the rev limiter to allow for the additional RPM increase, For consistency purposes if possible raising the rev limiter is the best solution.
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Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Thanks for the help. I have messed with that some but probably didnt have the rpm and speed set properly with speed satisfied first then rpm triggering the shift. Unfortunately I dont have any room to raise my rev limiter. I currently have an ls1 with a mostly stock bottom end. ARP rod bolts are the only update that I have done. I will have to lower my shift point. Unfortunately I dont have a suitable place to test with the nitrous except at the track. That wont be for a couple weeks. I am going to do some line pressure testing this week to make sure thats in order. Also going to check out some wiring.
Really appreciate all the help!!!
Really appreciate all the help!!!
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
I got an opportunity to get the car out to check line pressures on the car today.
With trans temp at normal operating temp of about 150F these are the numbers I got:
Park 70# @ 950rpm
Reverse 165# @ 950rpm
Neutral 70# @ 950rpm
1st gear 115# @ 950rpm
2nd thru OD 90-100# @ 950rpm
1st gear @ 6500rpm 150#
2nd gear @6500rpm 175#
Didn't do third gear.
Since the numbers were lower than I was told they should be, I unplugged the trans control plug and tested again.
With the control plug remove I could not move the car in 1st gear. (converter locked up possibly. Not sure why).
Put the shifter into OD at idle I got 240# of line pressure.
Wasn't able to do anymore than just idle around. Really thought I was going to wreck something.
The WOT numbers are quite a bit lower than PBA said they should be.
Since the line pressure went up with the trans control plug removed am I to believe it is in fact a tuning or sensor issue.
I really have no idea how to diagnose transmission issues.
Really need some advise on what to do next
With trans temp at normal operating temp of about 150F these are the numbers I got:
Park 70# @ 950rpm
Reverse 165# @ 950rpm
Neutral 70# @ 950rpm
1st gear 115# @ 950rpm
2nd thru OD 90-100# @ 950rpm
1st gear @ 6500rpm 150#
2nd gear @6500rpm 175#
Didn't do third gear.
Since the numbers were lower than I was told they should be, I unplugged the trans control plug and tested again.
With the control plug remove I could not move the car in 1st gear. (converter locked up possibly. Not sure why).
Put the shifter into OD at idle I got 240# of line pressure.
Wasn't able to do anymore than just idle around. Really thought I was going to wreck something.
The WOT numbers are quite a bit lower than PBA said they should be.
Since the line pressure went up with the trans control plug removed am I to believe it is in fact a tuning or sensor issue.
I really have no idea how to diagnose transmission issues.
Really need some advise on what to do next
TECH Junkie
Joined: Dec 2012
Posts: 3,621
Likes: 1,335
From: Iowa
Old school mod...turn the torx screw on the back of the pressure control solenoid 1/8 to 1/4 turn. This will increase line pressure.
There are better ways to do it, and a tune can fix the problem long term, but if you just want to check and see if things act better with increased line pressure, that's a cheap and easy approach.
again...not the best way, but probably the cheapest and easiest
There are better ways to do it, and a tune can fix the problem long term, but if you just want to check and see if things act better with increased line pressure, that's a cheap and easy approach.
again...not the best way, but probably the cheapest and easiest
As mentioned above you can turn the torx screw in back of pressure solenoid however beware later models the outer part may turn also if so you will need to hold it stationary you will understand what I mean if you do it,
But yes the reading you are getting at WOT do seem a bit off at WOT the readings should be within 10 percent of the unplugged readings so I would guess a tuning issue, seems like you will need to look at afl pressure setting in the tuning, I am still however not convinced this is your issue as if anything the lower line would allow the 3-4 clutch to slip after the shift command but you should very obviously feel, However getting the WOT line to at least 200 PSI would be the first order of the day and proceed from there,
But yes the reading you are getting at WOT do seem a bit off at WOT the readings should be within 10 percent of the unplugged readings so I would guess a tuning issue, seems like you will need to look at afl pressure setting in the tuning, I am still however not convinced this is your issue as if anything the lower line would allow the 3-4 clutch to slip after the shift command but you should very obviously feel, However getting the WOT line to at least 200 PSI would be the first order of the day and proceed from there,
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Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
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From: Devils Lake, ND
As mentioned above you can turn the torx screw in back of pressure solenoid however beware later models the outer part may turn also if so you will need to hold it stationary you will understand what I mean if you do it,
But yes the reading you are getting at WOT do seem a bit off at WOT the readings should be within 10 percent of the unplugged readings so I would guess a tuning issue, seems like you will need to look at afl pressure setting in the tuning, I am still however not convinced this is your issue as if anything the lower line would allow the 3-4 clutch to slip after the shift command but you should very obviously feel, However getting the WOT line to at least 200 PSI would be the first order of the day and proceed from there,
But yes the reading you are getting at WOT do seem a bit off at WOT the readings should be within 10 percent of the unplugged readings so I would guess a tuning issue, seems like you will need to look at afl pressure setting in the tuning, I am still however not convinced this is your issue as if anything the lower line would allow the 3-4 clutch to slip after the shift command but you should very obviously feel, However getting the WOT line to at least 200 PSI would be the first order of the day and proceed from there,
Performabuilt, I do agree that this is not the entire solution. I still must have my shift tables correct. Thank you
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Old school mod...turn the torx screw on the back of the pressure control solenoid 1/8 to 1/4 turn. This will increase line pressure.
There are better ways to do it, and a tune can fix the problem long term, but if you just want to check and see if things act better with increased line pressure, that's a cheap and easy approach.
again...not the best way, but probably the cheapest and easiest
There are better ways to do it, and a tune can fix the problem long term, but if you just want to check and see if things act better with increased line pressure, that's a cheap and easy approach.
again...not the best way, but probably the cheapest and easiest
Thank you maroon. Will give this a try. Working on doing it through my tune also. Appreciate the help
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
Did some testing the last few days. I've got my shift pressure at WOT up to between 210 and 220. Got some help from RPM and they agree with Performabuilt. They tell me my 2-3 shift mph is too close to actual and recommend lowering it from 81 to 76 mph. Going to give this a try. I may have to lower my shift times some. My latest log says my trans delivered torque at my 2-3 shift is 300-320ft-lb. If the shift goes as planned it will take about .300 seconds to complete. Seems like too long. Also thinking about changing my 2-3 shift down to 6000rpm. Make sure I get it shift on command and then start moving up closer to 6500 in small steps. If all else fails I will adjust my N20 to shut down at 6000rpm. Hoping to get to the track this weekend but they are predicting rain. Want this resolved
Last edited by snettell; Jun 14, 2016 at 08:22 PM.
Moderator
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From: Ann Arbor, MI
Sounds like you have HP Tuners or EFI Live for logging.
If so, you should be able to log e.g. "Force Motor (PCS) Line pressure %". If it isn't near 100% during a WOT shift, you have a tuning or engine sensor issue. While adjusting the screw on the PCS might have gotten your pressure up, IMHO adjusting the trans to compensate for a tuning/sensor issue is likely to bite you down the road.
If so, you should be able to log e.g. "Force Motor (PCS) Line pressure %". If it isn't near 100% during a WOT shift, you have a tuning or engine sensor issue. While adjusting the screw on the PCS might have gotten your pressure up, IMHO adjusting the trans to compensate for a tuning/sensor issue is likely to bite you down the road.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 60
Likes: 0
From: Devils Lake, ND
I have Hptuners but am not very good at using it. In my latest log, I am at 96% at both my 1-2 shift and 2-3 shift at WOT with a gauge pressure reading of between 210-220# pressure. I have not turned my PCS screw up at all to this point. The apparent increase in line pressure is purely do to operator error on my part during the original test with my gauge. I have a current NA log showing line pressure %, force motor desired and actual, delivered trans torque,shift time error and trans input and output shaft rpm. The problem I have is I dont rally know what it all means. Still trying to figure it out.