Question for NickTransmissions or anyone good w/4L65E/gmt800?

[someotherguy]

@NickTransmissions - sorry gang for the GMT800-related question but I've got 2 of 'em here and 1 has been giving me fits from the beginning. Bought a 2006 Silverado SS (RWD) LQ9 6.0 / 4L65E from the salvage auction back in late 2015. 80K miles when I bought it, hit in the rear, running and driving.

Gonna write a short novel and apologies in advance, there's a lot to unpack and I may have forgotten some details.

Noticed right away: ridiculously hard 1-2 shift, I mean, gonna break stuff hard. Took it to my local guy and he figured accumulator piston leaking or spring broken. Pulled the valve body and no evidence of problems there but he felt like maybe it had the wrong spring so he changed it. Found the typical check ball worn through the separator plate so he replaced that. New filter and back together. Still has a really firm 1-2 shift but no longer neck-snapping.

Couple years later the transmission croaks, IIRC first time around it was the sun shell grenaded. Lots of ugly noises. He built it for me and all was well for a while.

About a year later? I'm doing about 70 on the freeway and I'm almost home from work, notice the tach jump up a little bit like the converter unlocked. I go ahead and exit and baby it home (another 8 miles surface streets) and when I get to the house it's like the trans is binding up - doesn't really want to go forward very well, and almost won't reverse at all, like it's engaging several gears at once. Take it back to him and he tore it all down and didn't notice any real cause of failure until he saw some play in one of the drums - forgive me, direct drum? I'm no trans expert. He gets it all back together and again, it's fine for a while.

I've lost track now of what the third failure was (I think 3/4 clutches, started slipping on the freeway?) but he built it again. Mind you this guy has been building transmissions for me since the 80's and he's always been top notch, never had an issue with his work until THIS truck. This ongoing ordeal is pretty concerning but he's warrantied the work every time as he stands behind his work, plus we're old friends, but I'm worried it's gonna strain the relationship each time I have to go back.

So he's built the trans again, and it's fine for a while, until one cold morning I'm leaving work and get on the freeway and it flares up for a moment, couldn't even tell you what gear it was in at the time, I was dead tired and just getting started on a long trip home. Babied it home and it didn't happen again but I've been scared to mash the pedal ever since. It's been OK for months until the other day it acted up again but a little different, like it flared on the 1-2 just at part throttle at a gas station and kind of lingered like it wasn't in a gear for a moment, then it was OK. I checked the fluid and it was about 1.5 quarts low, looked OK. I don't see ANY evidence of leaks, pan is still dry, etc. but I added fluid til it shows full at the hot mark.

What the hell is going on with this transmission? The LQ9 is stock, not cammed or anything, but one big question mark is the tune. Since the truck came from the auction it's not like I have any history on what the previous owners have done with it. I really feel like I'm having an unreasonable amount of trouble with this transmission for a stock application that sees just daily driver usage, it's not like I'm street racing people with it. For comparison's sake, I got my wife practically the same exact truck (another 2006 Silverado SS) and the shifts on it are far, far tamer than my truck.

Any ideas? Thanks!
Richard

 

[NickTransmissions]

Hi Richard,

@NickTransmissions - sorry gang for the GMT800-related question but I've got 2 of 'em here and 1 has been giving me fits from the beginning. Bought a 2006 Silverado SS (RWD) LQ9 6.0 / 4L65E from the salvage auction back in late 2015. 80K miles when I bought it, hit in the rear, running and driving....

Any ideas? Thanks!
Richard

Here are my thoughts:

Harsh 1-2 Shift
He should have checked what second gear servo piston was installed (the 4L65Es that went into trucks had the 553 base servo while others that went into the GTOs, Vettes had the more aggressive 093 'Corvette' servo), servo travel and 1-2 shift feed hole size in the plate at the time the plate was repaired or replaced. Excessive servo travel will translate to an overly harsh 1-2 shift all other things equal and can be adjusted by replacing the pin w/a longer one (and grinding it down to obtain desired clearance if it wasn't already good as-is). If he drilled the 1-2 feed out to more than .086" and simply replaced the 1-2 accumulator housing springs with a stock spring set up, the shifts would likely be a bit harsh unless you had a 2500+ stall torque converter installed.

He should have also checked the TCC regulator valve in the valve body on the Sonnax vac test machine (I and most other trans builders have this equipment) - a worn bore will also cause a late, harsh 1-2 shift and usually set DTC P1870 though you didn't mention it throwing that particular code so perhaps that isn't part of the problem.

Who knows what he did or didn't do but those are all things that can add up to a harsh, late 1-2 shift.

Sun Shell Failure
Sun shell failure is common in those as it's made of relatively weak, soft metal. He should have installed a hardened, heat-treated version. The splines are heat-treated as the stock ones like to strip out or break off causing a loss of reverse, 2nd and 4th gears.

Loose Input Shaft
The input shaft was likely loose in the forward drum, causing massive leaks in the 3-4 clutch apply circuit burning up your 3-4 clutch pack. The overly harsh 1-2 shift which was probably untreated for countless drive cycles, would have been a contributory cause for this sort of failure. Those drums frequently leak at the drum/shaft junction where the steel shaft is pressed in to the aluminum drum - I always check for this upon tear down and inspection. The forward drum in the 700R4s and 4L60/65/70s is somewhat unique in the transmission world as it houses both the forward and direct (aka 3-4 clutch) clutch packs, along with the coast clutch pack. Most transmissions have a dedicated drum for each of those clutch packs....

Repeated 3-4 Clutch Failures
3-4 failure so soon after rebuild could be a few things but my guess is that the 3-4 clutch wasn't set up correctly or something else missed on tear down and inspection (like a leaking replacement drum); too much clearance and he may have reinstalled those stupid load release springs that came with it from the factory. They are one of the reasons that clutch is so vulnerable in those transmissions. I set clearance in stock applications to .050" and leave out the springs, which act against line pressure to keep the apply and backing plates apart when the trans isn't in 3rd or 4th gear to prevent centrifugal apply of that clutch. The springs aren't necessary however as the bleeder capsule in the drum is very efficient at venting fluid at higher RPM in 1st and 2nd so they cause more problems than they solve. He may also not be checking those drums for leaks but I'd be shocked if not given how long he's been building them - it's a well-known failure point since the 700R4s were in production in 82-93. High performance builds get .030-.040 clearance and high rate return springs and I only re-use the load release springs if clearance is .030 and RPMs are expected to exceed 6,000 on a reg basis.

Low Fluid
Sounds like a 2-3 shift flare occurred while you were getting on the freeway on that cold morning..Both flare episodes were likely caused by the fluid being low for months, assuming I'm interpreting the timeline correctly. All automatic transmissions are super-sensitive to fluid levels and being even just a quart low can generate drivability symptoms in certain conditions, especially at higher RPMs under moderate-heavy acceleration.

Tuning/Programming
How do you know the truck is tuned with a non-stock powertrain management program? What are the tune's parameters and where do they depart from the factory's tune?

My Questions
Hard to say what's really wrong with it without knowing more about what the builder did or didn't do per the above as repeated failures over a very short period of time like described are very uncommon unless there's another sub-system on the vehicle that is repeatedly failing/breaking down and adversely impacting the transmission. So...All that said, a few questions you'd want to ask your builder to find out:

1. Was the torque converter replaced at the time of the first rebuild and/or subsequent rebuilds (think there's like three recent overhauls on that trans now)?
2. Did he test the valve body for weakness in the actuator feed limit (AFL) or TCC regulator valves?
> If so, what were the results (how much vacuum did each retain?)
> Did he install updated valves that address the commonly occurring wear in those two bores?
3. Did he install any corrective shift kits or equivalent parts to address common hydraulic short comings (For example, I always install a new Sonnax o-ringed boost valve kit with upgraded PR spring, fix/convert the TCC reg valve from a PWM apply strategy to an on/off, repair AFL bore wear/install Sonnax oversized AFL valve and sleeve kit and delete the 3-2 downshift spring, blocking off that valve then take the original 3-2 spring and stick it inside the AFL main spring to improve AFL pressure characteristics for the solenoids)
4. Is he checking the band clearance upon reassembly? Here's what ideal band clearance looks like once the servo, band and two drums are in the case.
5. Is he testing the forward drum for leaks at the shaft?
6. Is he putting a straight edge to the worm tracks on the belly of the case and valve body to ensure both are flat (note this is usually not necessary on these transmissions but when one comes back repeatedly like yours has, it's worth checking)?
7. Did he machine the pump's working surfaces and checking rotor/slide to pump body deck surface clearance (clearance should be .001-.0015 for the rotor and .001-.002 for the slide - my machinist just machines them so that both are set at .001" clearance) when he overhauled the unit, at least for the first time - it almost certainly needed it
8. How is he setting up the 3-4 clutch pack?
> Is he reinstalling the load release springs?
> What is the clutch clearance he typically manages to?
> Did he install the 4L65E clutch pack (those units come with 7 .065" frictions and 6 .080" steels along with a 4L65E-specific apply and backing plate set)
9. Did he replace all of the bushings in the transmission upon the initial overhaul and any that were excessively worn once it came back each time?

Let me know what he says, if you decide to ask him any of the above. But if he's doing everything he should be then could be the transmission case itself is tweaked/warped but again - that is a very very rare occurrence and typically only happens when both engine and transmission severely overheat, usually many times before the case itself warps or somehow becomes compromised.

 

[someotherguy]

Hi Richard,



Here are my thoughts:

Harsh 1-2 Shift
He should have checked what second gear servo piston was installed (the 4L65Es that went into trucks had the 553 base servo while others that went into the GTOs, Vettes had the more aggressive 093 'Corvette' servo), servo travel and 1-2 shift feed hole size in the plate at the time the plate was repaired or replaced. Excessive servo travel will translate to an overly harsh 1-2 shift all other things equal and can be adjusted by replacing the pin w/a longer one (and grinding it down to obtain desired clearance if it wasn't already good as-is). If he drilled the 1-2 feed out to more than .086" and simply replaced the 1-2 accumulator housing springs with a stock spring set up, the shifts would likely be a bit harsh unless you had a 2500+ stall torque converter installed.

He should have also checked the TCC regulator valve in the valve body on the Sonnax vac test machine (I and most other trans builders have this equipment) - a worn bore will also cause a late, harsh 1-2 shift and usually set DTC P1870 though you didn't mention it throwing that particular code so perhaps that isn't part of the problem.

Who knows what he did or didn't do but those are all things that can add up to a harsh, late 1-2 shift.

Sun Shell Failure
Sun shell failure is common in those as it's made of relatively weak, soft metal. He should have installed a hardened, heat-treated version. The splines are heat-treated as the stock ones like to strip out or break off causing a loss of reverse, 2nd and 4th gears.

Loose Input Shaft
The input shaft was likely loose in the forward drum, causing massive leaks in the 3-4 clutch apply circuit burning up your 3-4 clutch pack. The overly harsh 1-2 shift which was probably untreated for countless drive cycles, would have been a contributory cause for this sort of failure. Those drums frequently leak at the drum/shaft junction where the steel shaft is pressed in to the aluminum drum - I always check for this upon tear down and inspection. The forward drum in the 700R4s and 4L60/65/70s is somewhat unique in the transmission world as it houses both the forward and direct (aka 3-4 clutch) clutch packs, along with the coast clutch pack. Most transmissions have a dedicated drum for each of those clutch packs....

Repeated 3-4 Clutch Failures
3-4 failure so soon after rebuild could be a few things but my guess is that the 3-4 clutch wasn't set up correctly or something else missed on tear down and inspection (like a leaking replacement drum); too much clearance and he may have reinstalled those stupid load release springs that came with it from the factory. They are one of the reasons that clutch is so vulnerable in those transmissions. I set clearance in stock applications to .050" and leave out the springs, which act against line pressure to keep the apply and backing plates apart when the trans isn't in 3rd or 4th gear to prevent centrifugal apply of that clutch. The springs aren't necessary however as the bleeder capsule in the drum is very efficient at venting fluid at higher RPM in 1st and 2nd so they cause more problems than they solve. He may also not be checking those drums for leaks but I'd be shocked if not given how long he's been building them - it's a well-known failure point since the 700R4s were in production in 82-93. High performance builds get .030-.040 clearance and high rate return springs and I only re-use the load release springs if clearance is .030 and RPMs are expected to exceed 6,000 on a reg basis.

Low Fluid
Sounds like a 2-3 shift flare occurred while you were getting on the freeway on that cold morning..Both flare episodes were likely caused by the fluid being low for months, assuming I'm interpreting the timeline correctly. All automatic transmissions are super-sensitive to fluid levels and being even just a quart low can generate drivability symptoms in certain conditions, especially at higher RPMs under moderate-heavy acceleration.

Tuning/Programming
How do you know the truck is tuned with a non-stock powertrain management program? What are the tune's parameters and where do they depart from the factory's tune?

My Questions
Hard to say what's really wrong with it without knowing more about what the builder did or didn't do per the above as repeated failures over a very short period of time like described are very uncommon unless there's another sub-system on the vehicle that is repeatedly failing/breaking down and adversely impacting the transmission. So...All that said, a few questions you'd want to ask your builder to find out:

1. Was the torque converter replaced at the time of the first rebuild and/or subsequent rebuilds (think there's like three recent overhauls on that trans now)?
2. Did he test the valve body for weakness in the actuator feed limit (AFL) or TCC regulator valves?
> If so, what were the results (how much vacuum did each retain?)
> Did he install updated valves that address the commonly occurring wear in those two bores?
3. Did he install any corrective shift kits or equivalent parts to address common hydraulic short comings (For example, I always install a new Sonnax o-ringed boost valve kit with upgraded PR spring, fix/convert the TCC reg valve from a PWM apply strategy to an on/off, repair AFL bore wear/install Sonnax oversized AFL valve and sleeve kit and delete the 3-2 downshift spring, blocking off that valve then take the original 3-2 spring and stick it inside the AFL main spring to improve AFL pressure characteristics for the solenoids)
4. Is he checking the band clearance upon reassembly? Here's what ideal band clearance looks like once the servo, band and two drums are in the case.
5. Is he testing the forward drum for leaks at the shaft?
6. Is he putting a straight edge to the worm tracks on the belly of the case and valve body to ensure both are flat (note this is usually not necessary on these transmissions but when one comes back repeatedly like yours has, it's worth checking)?
7. Did he machine the pump's working surfaces and checking rotor/slide to pump body deck surface clearance (clearance should be .001-.0015 for the rotor and .001-.002 for the slide - my machinist just machines them so that both are set at .001" clearance) when he overhauled the unit, at least for the first time - it almost certainly needed it
8. How is he setting up the 3-4 clutch pack?
> Is he reinstalling the load release springs?
> What is the clutch clearance he typically manages to?
> Did he install the 4L65E clutch pack (those units come with 7 .065" frictions and 6 .080" steels along with a 4L65E-specific apply and backing plate set)
9. Did he replace all of the bushings in the transmission upon the initial overhaul and any that were excessively worn once it came back each time?

Let me know what he says, if you decide to ask him any of the above. But if he's doing everything he should be then could be the transmission case itself is tweaked/warped but again - that is a very very rare occurrence and typically only happens when both engine and transmission severely overheat, usually many times before the case itself warps or somehow becomes compromised.

Thank you so much for the very detailed reply. It's going to be a lot more than I have the information for but I'll try to fill in a few blanks. Unfortunately since this has been going on over the course of almost 8 years now, lots of those answers may be "dunno"

One thing is that none of the failures were quick. There's always been a significant number of miles traveled before anything cropped up. I've doubled the miles on the truck since buying it in 2015 - 80K is now 160K+

Never had a P1870 and it wasn't a late 1-2 shift, it was just really harsh, so neither of us suspected the TCC valve bore wear. That's one I'm familiar with through other's experiences. He may have checked it initially regardless, don't know for sure.

It definitely got a hardened sun shell, that hasn't been an issue since the first rebuild. He's built several 4L60E's and 700R4's for me in the past and the hardened sun shell is always a given.

Whether or not the TC got replaced each time, I don't know. Since it's a "buddy deal" and each rebuild past the first has been warranty work, I've tended to not question him much as I'm just glad to get the truck back without having to set my wallet on fire.

And yes, timeline-wise both flare events were during the same rebuild interval (the most recent one) and I'll take the blame for not checking the fluid the first time around. Sometimes small but important details like that escape me because my schedule has me running like a madman for several days, then I have a few recovery days where I try to get things done.

I don't know if the tune is non-original. That's my comment on it being a question mark - I just have to wonder why this transmission behaves so differently than my wife's truck even though they're the same year and model; comparing behavior on the original 80K example of my truck, and 50K example of hers when we bought it. Hers seems "normal", mine was that super harsh 1-2 shift right off the bat, and the other shifts are firm (just not abusive-feeling.) Not having the history of any possible modifications since it's an auction truck, I have to just assume somebody was in there tinkering with something, whether mechanical or tune, or both. Tuning is a subject I haven't dove into yet, so any suggestions on reading the tune for checking things seems like a path to explore. Having a "normal" truck here to compare to as a baseline should help?

I'm a little reluctant to ask too many specifics of him since the rebuilds have happened over an 8 year period and 80K+ added miles. The most recent rebuild was around 20K miles and 1.5 years ago. It gets tricky as he's my friend and other than this truck, I've never had issues with his work; he builds transmissions all day long for probably 35+ years now and while anybody can overlook stuff I hate to imply to him that he might be doing something wrong. I've watched the guy work many times and he seems pretty meticulous.

I know, I know. Lots of moving parts (literally) and long-distance troubleshooting is always tricky, especially with limited info. Believe me though you've given me a lot to think about, just not sure how I might approach it. I'm crossing my fingers that it will behave with the added fluid but with the history, it's tough for me to have confidence.

Richard

 

[NickTransmissions]

Thank you so much for the very detailed reply. It's going to be a lot more than I have the information for but I'll try to fill in a few blanks. Unfortunately since this has been going on over the course of almost 8 years now, lots of those answers may be "dunno"

One thing is that none of the failures were quick. There's always been a significant number of miles traveled before anything cropped up. I've doubled the miles on the truck since buying it in 2015 - 80K is now 160K+

Never had a P1870 and it wasn't a late 1-2 shift, it was just really harsh, so neither of us suspected the TCC valve bore wear. That's one I'm familiar with through other's experiences. He may have checked it initially regardless, don't know for sure.

It definitely got a hardened sun shell, that hasn't been an issue since the first rebuild. He's built several 4L60E's and 700R4's for me in the past and the hardened sun shell is always a given.

Whether or not the TC got replaced each time, I don't know. Since it's a "buddy deal" and each rebuild past the first has been warranty work, I've tended to not question him much as I'm just glad to get the truck back without having to set my wallet on fire.

And yes, timeline-wise both flare events were during the same rebuild interval (the most recent one) and I'll take the blame for not checking the fluid the first time around. Sometimes small but important details like that escape me because my schedule has me running like a madman for several days, then I have a few recovery days where I try to get things done.

I don't know if the tune is non-original. That's my comment on it being a question mark - I just have to wonder why this transmission behaves so differently than my wife's truck even though they're the same year and model; comparing behavior on the original 80K example of my truck, and 50K example of hers when we bought it. Hers seems "normal", mine was that super harsh 1-2 shift right off the bat, and the other shifts are firm (just not abusive-feeling.) Not having the history of any possible modifications since it's an auction truck, I have to just assume somebody was in there tinkering with something, whether mechanical or tune, or both. Tuning is a subject I haven't dove into yet, so any suggestions on reading the tune for checking things seems like a path to explore. Having a "normal" truck here to compare to as a baseline should help?

I'm a little reluctant to ask too many specifics of him since the rebuilds have happened over an 8 year period and 80K+ added miles. The most recent rebuild was around 20K miles and 1.5 years ago. It gets tricky as he's my friend and other than this truck, I've never had issues with his work; he builds transmissions all day long for probably 35+ years now and while anybody can overlook stuff I hate to imply to him that he might be doing something wrong. I've watched the guy work many times and he seems pretty meticulous.

I know, I know. Lots of moving parts (literally) and long-distance troubleshooting is always tricky, especially with limited info. Believe me though you've given me a lot to think about, just not sure how I might approach it. I'm crossing my fingers that it will behave with the added fluid but with the history, it's tough for me to have confidence.

Richard

You're welcome, Richard...

Here's my advice: Ask him those questions. If he's your friend (or even just a stand-up business man and honest dealer) he will happily answer them and walk you through the details to the extent necessary to satisfy your query. For my part, I always keep an open door policy for my customers should questions arise. Additionally, I lay out everything I do to a given transmission so the customer knows what he's getting for his money as well as be confident I know what the hell I'm doing.

Assuming you approach in a diplomatic manner (i.e. non-accusatory) which I'm sure you will, he should have no qualms about discussing the particulars with you. Per your above, he seems like a rarity: a truly honest shop owner who wants the best for his customers and puts their interest first. Plus, we all have those 'problem children' transmissions that kick our ***** and put us through the ringer before we figure out what ails them and he's no different (im sure he has plenty of stories to tell).

All that said, some shops won't get into the details because either they suspect (rightly the overwhelming majority of the time) that the information will go right over the customer's head or because they simply prefer not to and that's how they are...No big deal as long as things are done right and warranties, if given, are honored during the warranty period. Sound like he has honored his warranty and stands behind his work so no concerns there.

But at the end of the day, it's your vehicle, your investment in time/money and faith in him that he's going to do the job right so at the very least, he owes you a conversation with some answers. Perhaps you/he can figure it out together...Re the tune, I'd assume it's factory but a quick scan of the trans or engine parameters by someone with HPTuners, EFI Live or similar software can confirm/deny.

If you want, feel free to invite him join this forum and PM me, assuming he's not already a member. I'd be glad to chat things over with him if he thinks a second pair of eyes (ears, really) would help. While I wouldn't expect him to take you/me up on that offer, it's on the table...I have a few builder friends where we call on each other every now and again in situations like this...It's part of the business (not the funnest part though haha).

Cheers.

 

[NickTransmissions]

Thank you so much for the very detailed reply...

Just occurred to me - Since you have a 4L65E, your forward drum has an induction-hardened input shaft with heat treated splines...Your pump's stator also has heat treated splines or at least it should if the original drum and pump are still installed in that transmission or actual 4L65E replacement parts were installed during the initial or subsequent overhauls.

Make sure your builder didn't swap those parts for 4L60E parts at any point in time (i.e. non-induction hardened, non-heat treated parts).