4L80E 'Soft Shift' Issue
Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
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From: Albuquerque, NM
4L80E 'Soft Shift' Issue Hello all,
I've got a very weird issue going on with my built 4L80E trans. Me and My tuner are having a hell of a time trying to figure out. I'll get straight to the point: I can't feel the transmission shifting
Took the car on its first test drive after dialing in the fueling, idle, etc... on the HPT VCM Scanner all the trans diag stuff is reading correctly, and the scanner is recording shifts 1-4 and downshifts as well, PRNDL status is accurate. However, i don't feel it shifting whatsoever, and if it is... its shifting super soft. I have a pretty big transgo shift kit in there. She just climbs the RPM's and goes, tach isn't dipping down when "shifting" like it is supposed to.All the data is saying im in good standing but my butt dyno is telling me otherwise lol.The car doesn't shudder, no slippage, I've already dropped the pan and inspected the fluid which it looked great, no clutch material. Solenoids... tested them all with a multimeter as well as the main harness inside and outside the trans, everything reads within spec. My tuner is telling me the car is running great based off the data, could it be my converter softening my shifts? I have the data log ready if anyone wants to take a look or if anyone had a similar issue to this how'd you get around it? Just want to take my car to the dyno to put some #'s down already
Any help is greatly appreciated. If any more info is needed let me know, and apologies for the long thread.
FYI: I followed the yank converter break-in instructions to the tee, threw a quart of fluid in the converter prior to install, it reads full on the dipstick and no codes are thrown.
My Setup:
1999 Pontiac Firebird Formula
-4.8L Single Turbo
-Local built 4L80E, forward pattern, no transbrake.
-Yank 3600 Stall Single Disk Lockup
-3.73 rear gear
-PCM of NC 4L80E adapter harness (NO SEGMENT SWAP NEEDED/USES 1 VSS (Output only)
-Stock 1999 5.7 LS1/4L60e PCM tuned via HPTuners w/ HPT Prolink
-E
I've got a very weird issue going on with my built 4L80E trans. Me and My tuner are having a hell of a time trying to figure out. I'll get straight to the point: I can't feel the transmission shifting
Took the car on its first test drive after dialing in the fueling, idle, etc... on the HPT VCM Scanner all the trans diag stuff is reading correctly, and the scanner is recording shifts 1-4 and downshifts as well, PRNDL status is accurate. However, i don't feel it shifting whatsoever, and if it is... its shifting super soft. I have a pretty big transgo shift kit in there. She just climbs the RPM's and goes, tach isn't dipping down when "shifting" like it is supposed to.All the data is saying im in good standing but my butt dyno is telling me otherwise lol.The car doesn't shudder, no slippage, I've already dropped the pan and inspected the fluid which it looked great, no clutch material. Solenoids... tested them all with a multimeter as well as the main harness inside and outside the trans, everything reads within spec. My tuner is telling me the car is running great based off the data, could it be my converter softening my shifts? I have the data log ready if anyone wants to take a look or if anyone had a similar issue to this how'd you get around it? Just want to take my car to the dyno to put some #'s down already
Any help is greatly appreciated. If any more info is needed let me know, and apologies for the long thread.FYI: I followed the yank converter break-in instructions to the tee, threw a quart of fluid in the converter prior to install, it reads full on the dipstick and no codes are thrown.
My Setup:
1999 Pontiac Firebird Formula
-4.8L Single Turbo
-Local built 4L80E, forward pattern, no transbrake.
-Yank 3600 Stall Single Disk Lockup
-3.73 rear gear
-PCM of NC 4L80E adapter harness (NO SEGMENT SWAP NEEDED/USES 1 VSS (Output only)
-Stock 1999 5.7 LS1/4L60e PCM tuned via HPTuners w/ HPT Prolink
-E
TECH Fanatic
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
"it reads full on the dipstick".
Original stick?
How much fluid is in the unit?
Dipstick fully in, pan off, where is the "full mark" in relation to the pan rail?
AIRC, there are 2 "stock" pans.
"She just climbs the RPM's and goes, tach isn't dipping down when "shifting" like it is supposed to."
What does Yank say about the issue?
Original stick?
How much fluid is in the unit?
Dipstick fully in, pan off, where is the "full mark" in relation to the pan rail?
AIRC, there are 2 "stock" pans.
"She just climbs the RPM's and goes, tach isn't dipping down when "shifting" like it is supposed to."
What does Yank say about the issue?
Is a converter break in a thing?? Never heard of that before. Are you sure that's a 3600 converter in there and not something wild like a 5000?? If there's no rpm drop on shifts it could just be a really loose converter
Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
Likes: 12
From: Albuquerque, NM
I'm using one of those Lokar knock off dipsticks. Not a big fan of it. I've checked the placement of the end of the dipstick which sits just a little past the valvebody. I'm using a stock style TCI pan. I also have about 14qts of fluid inside the unit as specified by my builder.
As for reaching out to Yank, I thought they were closed on the weekends, so I'm waiting til tomorrow to reach out to them about the issue but figured I'd ask here while I wait.
As for reaching out to Yank, I thought they were closed on the weekends, so I'm waiting til tomorrow to reach out to them about the issue but figured I'd ask here while I wait.
Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
Likes: 12
From: Albuquerque, NM
Z28, let me rephrase that lol, not necessarily a 'break-in' sheet, just a list of Do's and Don'ts.
And man I sure hope they didn't send me a 5000 stall, their website listing only said 3600 stall on it!
But I agree, it feels super loose and if it's shifting I can't feel anything lol
And man I sure hope they didn't send me a 5000 stall, their website listing only said 3600 stall on it!
But I agree, it feels super loose and if it's shifting I can't feel anything lol
TECH Fanatic
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
If..... Z28, let me rephrase that lol, not necessarily a 'break-in' sheet, just a list of Do's and Don'ts.
And man I sure hope they didn't send me a 5000 stall, their website listing only said 3600 stall on it!
But I agree, it feels super loose and if it's shifting I can't feel anything lol
And man I sure hope they didn't send me a 5000 stall, their website listing only said 3600 stall on it!
But I agree, it feels super loose and if it's shifting I can't feel anything lol
3600... could be 3600 at some given power input, it could have the wrong stator, yadda yadda.
You have a part number?
A call to Yank is in order.
Z28, let me rephrase that lol, not necessarily a 'break-in' sheet, just a list of Do's and Don'ts.
And man I sure hope they didn't send me a 5000 stall, their website listing only said 3600 stall on it!
But I agree, it feels super loose and if it's shifting I can't feel anything lol
And man I sure hope they didn't send me a 5000 stall, their website listing only said 3600 stall on it!
But I agree, it feels super loose and if it's shifting I can't feel anything lol
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Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
Likes: 12
From: Albuquerque, NM
Buzzard, I did speak to Dave from Yank and detailed what I was putting the converter behind, mainly was trying to figure out the proper flexplate to mate everything together. He didn't speak against my option & didn't tell me to go a different route. The part no. on the box and the invoice is PY3600/4L80LS. It's their Pro Yank Series converter listed on their website. But I 100% agree, a call is definitely in order.
Z28, I agree on this as well, got hit with some crappy weather as I'm trying to figure all of this out. If the pressures do read low on the gauge, would I have to drop the vb? Line pressure on the scanner is reading great, was hoping its not a vb malfunction. My tuner is also suspicious that something is up with the converter as well.
Z28, I agree on this as well, got hit with some crappy weather as I'm trying to figure all of this out. If the pressures do read low on the gauge, would I have to drop the vb? Line pressure on the scanner is reading great, was hoping its not a vb malfunction. My tuner is also suspicious that something is up with the converter as well.
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Verdad Gallardo Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
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From: Albuquerque, NM
Threw the data log in that last post if anyone would like to take a look. I have all my trans diag in the channels towards the very bottom. The driving in this log doesn't start til the 3 min mark.
SIDE NOTE: Towards the end youll see the solenoids all turning on and off, I had my pops try to command the shifts on the scanner, still didn't feel any "lurch" from the car. I do have another log here without commanding any shifts from the scanner. Driving starts at the 3:27 min mark.
SIDE NOTE: Towards the end youll see the solenoids all turning on and off, I had my pops try to command the shifts on the scanner, still didn't feel any "lurch" from the car. I do have another log here without commanding any shifts from the scanner. Driving starts at the 3:27 min mark.
Last edited by emajioo; May 4, 2025 at 04:05 PM. Reason: adding more useful information to post
Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
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From: Albuquerque, NM
Spoke to Yank about the issue and they said with this specific converter, I should be feeling my shifts no problem and seeing the substantial RPM drop on the tach. More than likely hinting at a problem with my trans.
My tuner however suggested to try and get it above stall speed or somewhere around 50% throttle, if it does the same thing and I still don't feel a shift then there is an issue with the trans. I am going to be taking it back out here shortly, will follow up with whatever happens in the meantime.
My tuner however suggested to try and get it above stall speed or somewhere around 50% throttle, if it does the same thing and I still don't feel a shift then there is an issue with the trans. I am going to be taking it back out here shortly, will follow up with whatever happens in the meantime.
I don't get very deep in trans tuning, so my questions/comments are probably pointless.
I don't see any RPM change when it shifts.
I also didn't see the MAP value change at all on the shift, I would "expect" the load to change on the engine after a gear change.
At some points in the logs, there's almost a 2,000rpm difference between the input and output sensor.
Is that due to stall?
OP, have you locked up the converter during shifts to see how it acts? I mean just for testing purposes.
I don't see any RPM change when it shifts.
I also didn't see the MAP value change at all on the shift, I would "expect" the load to change on the engine after a gear change.
At some points in the logs, there's almost a 2,000rpm difference between the input and output sensor.
Is that due to stall?
OP, have you locked up the converter during shifts to see how it acts? I mean just for testing purposes.
Thread Starter
Teching In
Joined: Jan 2023
Posts: 42
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From: Albuquerque, NM
Jay, appreciate you taking the time to look through the log! I've looked through it over and over and I don't see any of the values really changing either as I shift, and if they are its not drastic like it should be.The ISS/OSS RPM difference.. I'm unsure about. I have not tried locking up the converter yet, I was going to get around to that this evening but as I was pulling the car out of the driveway I had a power steering line rupture and **** fluid all over the engine bay, then it started raining right on me after that. Did I mention God loves me?
However I digress, I got the line fixed and should be able to resume testing it tomorrow after I get off work. I'll follow up then
-E
However I digress, I got the line fixed and should be able to resume testing it tomorrow after I get off work. I'll follow up then
-E
Jay, appreciate you taking the time to look through the log! I've looked through it over and over and I don't see any of the values really changing either as I shift, and if they are its not drastic like it should be.The ISS/OSS RPM difference.. I'm unsure about. I have not tried locking up the converter yet, I was going to get around to that this evening but as I was pulling the car out of the driveway I had a power steering line rupture and **** fluid all over the engine bay, then it started raining right on me after that. Did I mention God loves me?
However I digress, I got the line fixed and should be able to resume testing it tomorrow after I get off work. I'll follow up then
-E
However I digress, I got the line fixed and should be able to resume testing it tomorrow after I get off work. I'll follow up then
-E
Hmmm yea that shouldn't be a thing. If I were OP that's where I'd start before tearing it all down. If those sensors are leaving the party then he's most definitely gonna have shifting issues
The OP listed he used an adapter harness from PCM of NC, and only uses one VSS.
I'm going to "guess" that it uses the OSS to determine shift speed only?
I'm not familiar with that, what it changes and what the benefits are.
I'm going to "guess" that it uses the OSS to determine shift speed only?
I'm not familiar with that, what it changes and what the benefits are.
I put the ISS and OSS in the chart, and they drop out multiple times through out the log.
I don't know how accurate the TCC applied PID is, but it says it's applied in 1st and 2nd gear at times.
I don't know how accurate the TCC applied PID is, but it says it's applied in 1st and 2nd gear at times.