Limp mode?
12-14-2017, 12:25 PM
#1
Limp mode? Hi guys,
I am soliciting assistance once again.
Trans has been back in the truck about 12-13 weeks now, problem free.
1. I had a center support bearing go bad, that was replaced.
2. I think while babying it home after #1, it caused the pinion to break (since I pulled a 3in chunk of it out of the rear diff), that was replaced with a 4.56 setup.
3. A replacement tailshaft was installed since the seal had started leaking. I put in a new VSS at this time also.
Ok, here is where it gets interesting.
AFTER, I get it all back together with the new gears (went from 4.10 to 4.56), it would fall out of 4th gear, into 3rd and the TCC would lock. If I stop, it will resume normal operation.
The problem is intermittent. It may take 25min before it happens or it may take 5min.
1. HPT says the commanded gear is 4th. :/
2. No amount of tuning has remedied the issue.
3. I did flush the fluid out. It was dirty but nothing alarming about it.
4. I put the old VSS back in and unplugged the trans connector and reconnected it just to ensure that it was connected securely.
5. Changed plugs/wires
6. No misfires
7. PCM has misfires disabled
8. Ignition switch has been replaced.
I've read about "reprogram PCM for VSS dropoff" but I cannot find any decent details as to what to do in HPT.
This morning, it started doing 3rd gear starts, until I switched it off, then I had first gear again.
Help, please. I am about to burn it to the ground but I love my truck. LOL.
Let me be clear. I have all gears and it will even go into 4th and lockup but will go into 3rd and lock the converter after some time. It could be 5 minutes or 25 minutes.
It's a 2006 Sierra, 2wd. 3800 loose converter, 4.56s.
Thanks in advance,
I am soliciting assistance once again.
Trans has been back in the truck about 12-13 weeks now, problem free.
1. I had a center support bearing go bad, that was replaced.
2. I think while babying it home after #1, it caused the pinion to break (since I pulled a 3in chunk of it out of the rear diff), that was replaced with a 4.56 setup.
3. A replacement tailshaft was installed since the seal had started leaking. I put in a new VSS at this time also.
Ok, here is where it gets interesting.
AFTER, I get it all back together with the new gears (went from 4.10 to 4.56), it would fall out of 4th gear, into 3rd and the TCC would lock. If I stop, it will resume normal operation.
The problem is intermittent. It may take 25min before it happens or it may take 5min.
1. HPT says the commanded gear is 4th. :/
2. No amount of tuning has remedied the issue.
3. I did flush the fluid out. It was dirty but nothing alarming about it.
4. I put the old VSS back in and unplugged the trans connector and reconnected it just to ensure that it was connected securely.
5. Changed plugs/wires
6. No misfires
7. PCM has misfires disabled
8. Ignition switch has been replaced.
I've read about "reprogram PCM for VSS dropoff" but I cannot find any decent details as to what to do in HPT.
This morning, it started doing 3rd gear starts, until I switched it off, then I had first gear again.
Help, please. I am about to burn it to the ground but I love my truck. LOL.
Let me be clear. I have all gears and it will even go into 4th and lockup but will go into 3rd and lock the converter after some time. It could be 5 minutes or 25 minutes.
It's a 2006 Sierra, 2wd. 3800 loose converter, 4.56s.
Thanks in advance,
12-17-2017, 10:06 AM
#3
Moderator
To simplify your post, you are saying that at some time the trans will go from 4th gear with lockup to 3rd gear with lockup and HP Tuners shows that 4th is commanded. Correct?
Here are the most common problem ways in which the tran is in 3rd gear when 4th is commanded:
* Worn band, which be tested by estimating the end play of the servo.
* Servo problem, such as a worn seal, cracked piston.
* Problem in the valve body, such as a sticking valve.
Since your problem is intermittent, a bad valve body (VB) is a likely candidate.
I would still check the servo end play by pressing on the servo cover with a crowbar and while holding a small ruler nearby, estimate how much is moves in. 1/16 to 1/8" is spec and anything over 3/8" indicates a worn band that will soon slip in 2nd or 4th gear.
We had an older one and recently had another post where replacing the VB restored 4th gear for the OP. While there probably are only two valves (3-4 shift, 3-4 shuttle) that move from 3rd to 4th gear, the OP decided to just replace the VB instead of trying to rebuild it.
It is a bit confusing that you called this thread "Limp Mode" and indeed mention entering limp mode on occasion. I think that is a separate problem, partly because the converter is unlikely to be locked in limp mode.
Here are the most common problem ways in which the tran is in 3rd gear when 4th is commanded:
* Worn band, which be tested by estimating the end play of the servo.
* Servo problem, such as a worn seal, cracked piston.
* Problem in the valve body, such as a sticking valve.
Since your problem is intermittent, a bad valve body (VB) is a likely candidate.
I would still check the servo end play by pressing on the servo cover with a crowbar and while holding a small ruler nearby, estimate how much is moves in. 1/16 to 1/8" is spec and anything over 3/8" indicates a worn band that will soon slip in 2nd or 4th gear.
We had an older one and recently had another post where replacing the VB restored 4th gear for the OP. While there probably are only two valves (3-4 shift, 3-4 shuttle) that move from 3rd to 4th gear, the OP decided to just replace the VB instead of trying to rebuild it.
It is a bit confusing that you called this thread "Limp Mode" and indeed mention entering limp mode on occasion. I think that is a separate problem, partly because the converter is unlikely to be locked in limp mode.
12-18-2017, 09:59 AM
#4
To simplify your post, you are saying that at some time the trans will go from 4th gear with lockup to 3rd gear with lockup and HP Tuners shows that 4th is commanded. Correct?
Here are the most common problem ways in which the tran is in 3rd gear when 4th is commanded:
* Worn band, which be tested by estimating the end play of the servo.
* Servo problem, such as a worn seal, cracked piston.
* Problem in the valve body, such as a sticking valve.
Since your problem is intermittent, a bad valve body (VB) is a likely candidate.
I would still check the servo end play by pressing on the servo cover with a crowbar and while holding a small ruler nearby, estimate how much is moves in. 1/16 to 1/8" is spec and anything over 3/8" indicates a worn band that will soon slip in 2nd or 4th gear.
We had an older one and recently had another post where replacing the VB restored 4th gear for the OP. While there probably are only two valves (3-4 shift, 3-4 shuttle) that move from 3rd to 4th gear, the OP decided to just replace the VB instead of trying to rebuild it.
It is a bit confusing that you called this thread "Limp Mode" and indeed mention entering limp mode on occasion. I think that is a separate problem, partly because the converter is unlikely to be locked in limp mode.
Here are the most common problem ways in which the tran is in 3rd gear when 4th is commanded:
* Worn band, which be tested by estimating the end play of the servo.
* Servo problem, such as a worn seal, cracked piston.
* Problem in the valve body, such as a sticking valve.
Since your problem is intermittent, a bad valve body (VB) is a likely candidate.
I would still check the servo end play by pressing on the servo cover with a crowbar and while holding a small ruler nearby, estimate how much is moves in. 1/16 to 1/8" is spec and anything over 3/8" indicates a worn band that will soon slip in 2nd or 4th gear.
We had an older one and recently had another post where replacing the VB restored 4th gear for the OP. While there probably are only two valves (3-4 shift, 3-4 shuttle) that move from 3rd to 4th gear, the OP decided to just replace the VB instead of trying to rebuild it.
It is a bit confusing that you called this thread "Limp Mode" and indeed mention entering limp mode on occasion. I think that is a separate problem, partly because the converter is unlikely to be locked in limp mode.
I guess with the inherent question mark, I still didn't explain it well enough.
I assumed it was limp mode but based on your feedback, it isn't.
And yes, it would revert to 3rd gear, locked, while the scanner displayed 4th, locked. I have the logs.
I'm also been wondering if it was a tuning issue that decided to rear its ugly head after I installed the new gears.
New gears (4.56) = more cruise rpm = more demand for line pressure
Thoughts on the above?
I've been playing with the force motor table more the last few days and today has been the first day that I have driven to/from work without it having issues.
Meaning, it stayed in 4th, locked the entire time. No issues.
My 0 column in the force motor table is about 380 right now and according to the scanner, 0 pressure is commanded while under light throttle and cruising.
12-18-2017, 11:44 AM
#6
12-18-2017, 08:16 PM
#7
Moderator
I also don't think this is a pressure problem nor a tuning problem.
You can start by measuring (at least estimating with a ruler) how much the servo cover moves in when you press on it with a crowbar (or about 50 lbs). Assuming this is a new(ish) trans/rebuild that will eliminate a worn band.
When was the trans last rebuilt? It could be a servo problem due to worn seals.
Since you have HP Tuners and willingness to tinker with the trans, why not get a trans pressure gauge. (ATD-5550 for $44 on Amazon) You can then (later?) confirm that any tuning changes are really taking effect. Just because you stick some numbers into the tune doesn't mean that is what you will actually get.
Then once we confirm the band isn't worn, an inspection shows the servo not to have worn/broken seals or cracked pistons, and confirm the the trans line pressure is OK, IMHO I would then suggest buying a rebuilt valve body.
Perhaps one of the pros will confirm or correct me, or suggest a different plan, but unless they do, how is that plan?
You can start by measuring (at least estimating with a ruler) how much the servo cover moves in when you press on it with a crowbar (or about 50 lbs). Assuming this is a new(ish) trans/rebuild that will eliminate a worn band.
When was the trans last rebuilt? It could be a servo problem due to worn seals.
Since you have HP Tuners and willingness to tinker with the trans, why not get a trans pressure gauge. (ATD-5550 for $44 on Amazon) You can then (later?) confirm that any tuning changes are really taking effect. Just because you stick some numbers into the tune doesn't mean that is what you will actually get.
Then once we confirm the band isn't worn, an inspection shows the servo not to have worn/broken seals or cracked pistons, and confirm the the trans line pressure is OK, IMHO I would then suggest buying a rebuilt valve body.
Perhaps one of the pros will confirm or correct me, or suggest a different plan, but unless they do, how is that plan?
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12-18-2017, 08:56 PM
#10
Moderator
Jay, thanks for finding the finding the earlier thread, the OP should have started with that. (I wasn't very active on this forum in July - road course racing most weekends.)
Some metal fragments from the sprag failure might be lodged in the valve body.
In previous somewhat-similar threads, the OPs didn't want to bother disassembling the valve body and simply bought a rebuilt one which fixed their 4th gear problem. Obviously you (Jay) and I would disassemble and clean it. I wish they had sent the bad VB to me because I want to know exactly which valve causes these problems. (3-4 shift valve, 3-4 relay valve, 4-3 sequence valve)
Some metal fragments from the sprag failure might be lodged in the valve body.
In previous somewhat-similar threads, the OPs didn't want to bother disassembling the valve body and simply bought a rebuilt one which fixed their 4th gear problem. Obviously you (Jay) and I would disassemble and clean it. I wish they had sent the bad VB to me because I want to know exactly which valve causes these problems. (3-4 shift valve, 3-4 relay valve, 4-3 sequence valve)
12-19-2017, 04:58 PM
#12
It's hard to say over the internet, when so much has been done.
It could be programming, but you'd have to let someone look at it, like post the tune.
It could be a tiny fragment of anything due to the multiple rebuilds.
It could be external, or internal wiring.
I'm going off the assumption you're logging temperature, a slip can cause overheating which can cause what you describe.
No DTC's? Well which ones have been disabled....
And since it ran several weeks, maybe it's a bushing or something that went in a little sideways, tight, loose, finally turned in it's bore causing an internal leak.
Could be improperly torqued valve body bolts.
It could be so much stuff. Typically you spend time accumulated up to hours trying to help someone and they don't listen, ask for advice but do something else, or end it by saying it was taken to a shop.
Are you willing to tear it down and inspect everything?
It could be programming, but you'd have to let someone look at it, like post the tune.
It could be a tiny fragment of anything due to the multiple rebuilds.
It could be external, or internal wiring.
I'm going off the assumption you're logging temperature, a slip can cause overheating which can cause what you describe.
No DTC's? Well which ones have been disabled....
And since it ran several weeks, maybe it's a bushing or something that went in a little sideways, tight, loose, finally turned in it's bore causing an internal leak.
Could be improperly torqued valve body bolts.
It could be so much stuff. Typically you spend time accumulated up to hours trying to help someone and they don't listen, ask for advice but do something else, or end it by saying it was taken to a shop.
Are you willing to tear it down and inspect everything?
12-20-2017, 05:15 AM
#13
It's hard to say over the internet, when so much has been done.
It could be programming, but you'd have to let someone look at it, like post the tune.
It could be a tiny fragment of anything due to the multiple rebuilds.
It could be external, or internal wiring.
I'm going off the assumption you're logging temperature, a slip can cause overheating which can cause what you describe.
No DTC's? Well which ones have been disabled....
And since it ran several weeks, maybe it's a bushing or something that went in a little sideways, tight, loose, finally turned in it's bore causing an internal leak.
Could be improperly torqued valve body bolts.
It could be so much stuff. Typically you spend time accumulated up to hours trying to help someone and they don't listen, ask for advice but do something else, or end it by saying it was taken to a shop.
Are you willing to tear it down and inspect everything?
It could be programming, but you'd have to let someone look at it, like post the tune.
It could be a tiny fragment of anything due to the multiple rebuilds.
It could be external, or internal wiring.
I'm going off the assumption you're logging temperature, a slip can cause overheating which can cause what you describe.
No DTC's? Well which ones have been disabled....
And since it ran several weeks, maybe it's a bushing or something that went in a little sideways, tight, loose, finally turned in it's bore causing an internal leak.
Could be improperly torqued valve body bolts.
It could be so much stuff. Typically you spend time accumulated up to hours trying to help someone and they don't listen, ask for advice but do something else, or end it by saying it was taken to a shop.
Are you willing to tear it down and inspect everything?
With that being said, I'll include my tune, config files, etc for someone to review.
Thanks.
12-20-2017, 07:11 AM
#15
Yea,
Trying to troubleshoot the issue myself I had HPT add support for some additional trans parameters for my OS id.
Here is the link to the 3.7 beta:
https://drive.google.com/file/d/1tNL...ew?usp=sharing
12-20-2017, 12:50 PM
#17
I've always thought it was an internal transmission problem.
The programming looks ok, except you keep bumping the pressure up and saying it's helping. I think because the leak was getting worse.
I thought of this the other day. I'm building a 4L60E for something and had to tear down three cores so far because I haven't found all good hard parts.
I tore this one down that looked like a good, fairly new rebuild, new electrical and all. I look at the big things first, sure enough 3-4 was burned up. I'm going to end up using that whole transmission.
Then I saw this, my worst nightmare. Getting one together but probably shaved the ring during final assembly. I bet it ran good at first and slowly started slipping, then they must have said f it and thats how it ended up as a core.
Seems like what happened to yours, something slowly wore out. I knew the tune wouldn't do it.
https://ls1tech.com/forums/attachmen...1&d=1513795739
The programming looks ok, except you keep bumping the pressure up and saying it's helping. I think because the leak was getting worse.
I thought of this the other day. I'm building a 4L60E for something and had to tear down three cores so far because I haven't found all good hard parts.
I tore this one down that looked like a good, fairly new rebuild, new electrical and all. I look at the big things first, sure enough 3-4 was burned up. I'm going to end up using that whole transmission.
Then I saw this, my worst nightmare. Getting one together but probably shaved the ring during final assembly. I bet it ran good at first and slowly started slipping, then they must have said f it and thats how it ended up as a core.
Seems like what happened to yours, something slowly wore out. I knew the tune wouldn't do it.
https://ls1tech.com/forums/attachmen...1&d=1513795739
Last edited by Jays_SSZ28; 12-22-2017 at 09:23 PM.
12-20-2017, 01:18 PM
#18
I've always thought it was an internal transmission problem.
The programming looks ok, except you keep bumping the pressure up and saying it's helping. I think because the leak was getting worse.
I thought of this the other day. I'm building a 4L60E for something and had to tear down three cores so far because I haven't found all good hard parts.
I tore this one down that looked like a good, fairly new rebuild, new electrical and all. I look at the big things first, sure enough 3-4 was burned up. I'm going to end up using that whole transmission.
Then I saw this, my worst nightmare. Getting one together but probably shaved the ring during final assembly. I bet it ran good at first and slowly started slipping, then they must have said f it and thats how it ended up as a core.
Seems like what happened to yours, something slowly wore out. I knew the tune wouldn't do it.
https://ls1tech.com/forums/attachmen...1&d=1513795739
The programming looks ok, except you keep bumping the pressure up and saying it's helping. I think because the leak was getting worse.
I thought of this the other day. I'm building a 4L60E for something and had to tear down three cores so far because I haven't found all good hard parts.
I tore this one down that looked like a good, fairly new rebuild, new electrical and all. I look at the big things first, sure enough 3-4 was burned up. I'm going to end up using that whole transmission.
Then I saw this, my worst nightmare. Getting one together but probably shaved the ring during final assembly. I bet it ran good at first and slowly started slipping, then they must have said f it and thats how it ended up as a core.
Seems like what happened to yours, something slowly wore out. I knew the tune wouldn't do it.
https://ls1tech.com/forums/attachmen...1&d=1513795739
I appreciate your thoughts and transparency. I'm weighing my options currently.
My only gripe with RPM is that they blamed me for breaking the trans. I did pay a handsome price for the Level7 and it did perform well. It took 14psi from a Whipple, that was on a 6.0 that made 9psi at 2k. It never flinched.
I have emailed Jeremy and as I said in my email to him, I'm eating my crow and need help.
He seems open to assisting.