4T65E Hard Shift-Solution
- Thread starter jbamonte
- Start date
I used the ZZ Performance first on my tranny but switched to the Transgo shift kit later since it is a much better package-shims and NEW springs in the accumulator versus shims only for the ZZ performance kit. I am at 160,000 miles now on the 4T65E and since I addressed this issue at 90,000 miles, the tranny has been perfect! This fix is not a temporary issue if the only issue is a 1811 hard shift problem-it clearly works BUT you really need to address the high Trans fluid temp that the trans will reach cooling the fluid through the radiator. Mount the biggest double stack cooler you can in the grille (I have 2 Dana/Long 18,000 GVW coolers on either side of the nose air intakes in the grille) and remove all cooling from the radiator. Even this past winter when it was brutally cold, no issues as long as you are easy on the trans until the fluid gets hot enough to switch into overdrive (88 degrees trans fluid temp). I still wonder how many folks have spend hundreds and even thousands on these transmissions for this issue when the fix is relatively inexpensive and easy. Good luck!
Excellent! Another saved 4T65E tranny!
Another tip is to change the fluid and filter often, much more often than GM recommends or others for that matter. My 2001 GP is driven about 25,000 miles per year and I have been changing the trans and filter every year now for the last 5 years, especially since the mileage is getting high now. I drive mostly highway, high speed-aveage is about 80 MPH, but do not beat on the tranny at all. If you do mostly highway and are nice to the tranny, I would think you could go longer between trans fluid/filter changes but I would not go more than 35,000 miles-just me-doing this a long time. If you do mostly stop and go driving, I would change the fluid/filter, once a year, regardless of mileage. I use Walmart Supertec Dexron VI-$4/QT, NOT Dexron III-OEM Fluid Specified by GM before Dexron VI was available. Dexron VI is a MUCH better trans fluid-use it and it is backward compatible to Dexron III. Do not listen to the forum "experts" who are not! Trans fluid change will cost 8.5 QTs x $4/Qt=$34 +20 for the filter=$54. It's the best $50 you can spend on your GP and MUCH cheaper than $2-3K for a rebuilt junk tranny, unless you get a specialized 4T65E beefed up from a vendor like Triple Edge Performance-not to mention the time and effort to make the switch.
Hope that helps!
Bronco Boy
Donating Users
Just to clarify for future readers.....
The shift kit is not a fix, it is a band-aid/temporary solution. Until the problem (typically PCS) is replaced, you have not "fixed" the problem.
This statement is incorrect!
The 1811 code (PCS) first showed up in my GP at 90,000 miles and after installing the Transgo shift kit and the tranny coolers with the cooling outside of the factory radiator cooling, the trans now has 160,000 miles on it. The hard shift issue has NOT occurred once in 70,000 miles of all types of driving-so much for a temporary fix-that was 5 years ago. The issue has been fixed on my car.
I have to agree more with jbamonte. The PCS is NOT necessarily the cause of the P1811. There was an early GM TSB that specified that as the remedy. But over time it became clear that many transmissions that had gotten the TSB-specified PCS replacement continued to have the same problems. Back when I had one of these POS transmissions I spent countless hours trying to get to the bottom of this issue (both at prof shops and online), and the fact is that even GM has no clear handle on the causes of issues with these transmissions.
And that is actually why I call it a POS transmission. I am aware that when they work properly they are very nice transmissions. It's just that when they don't work appropriately, finding any answers about the causes of malfunctions is practically impossible. I'm pretty sure it's just a complex system problem - multiple interacting failures where the "cause" is not in any one part. It is certainly NOT as simple as the PCS.
I can't give any updates on my own transmission / shift kit install because a blown head gasket sent the thing to the scrap yard quite a while ago. But I do regard this shift kit as the only thing you can really find that provides a fix. Whether it just compensates for other multiple interacting system failures or whatever, I can't say. But it works perfectly and reliably. As such I do regard is a fix rather than a band-aid.
I am getting ready for my pretty much annual Tranny fluid/filter change within the next few weeks since I have a 1,000 miles trip the GP is going on in early June-25,000 miles since the last change. I will report back on the fluid and pan condition at that time. I have been using Dexron VI for the last 5 years-Walmart Supertech and a Wix filter-Apprx $50. The pan is always super clean and the fluid always looks real good.
Bronco Boy
Donating Users
But you still have a broken part(s) in the vehicle. Until it is replaced, you have a band-aid. Possibly a really good band-aid, but a band-aid none the less.
Correct, thus why I said "typically".
the PCS electrically controls the pump line pressure in conjunction with the mechanical control from the springs/shims in the accumulator. The Transgo shift kit replaces the shims/springs in the accumulator and effectively transfers the line pressure control previously performed by the accumulator AND the PCS solenoid to having all control of the shift/line pressure to the accumulator ONLY, since the PCS is no longer working correctly which is the E in the 4T65E trans name. This control is basically the same control found in the 4T60 previous version of the transmission, and the mechanical control used in transmissions forever prior to the electronic versions. An inoperable PCS corrected with a shift kit will operate correctly forever if that is the only issue and has zero effective on the operation of the transmission and mileage. It is a permanent fix for a hard shift condition caused by the PCS-replaces one type of control with another.
Not sure you have a very good understanding of the operation of your transmission... I just looked at the kit in question quick and it is replacing things in the 1-2 and 2-3 accumulators. Neither of which have any control of line pressure.
E stands for electronically controlled transmission, it only signifies it is shifted electronically. The 4T60E trans is a good example of that. It is electronically shifted yet line pressure is controlled by engine vacuum.
Most of the time I see 4T65's with habitual harsh shifts it ends up being the torque signal regulator valve in the valve body binding. Religious filter and fluid changes probably do more good than the shift kit.
Sent from my SCH-R970 using Tapatalk
You are correct! I am NOT a 4T65E transmission expert BUT I do have over 30 years experiencing working on my own cars, and no I do not mean tuneups. Transgo, on the other hand, has more experience with transmissions than most folks on the forum. I went back and looked at the Transgo shift kit instructions for the benefit of us novices and refreshed my knowledge on this whole hard shift issue (my temporary fix has lasted 5 years and 70,000 miles now) as to why their shift kit works to correct this hard shift issue. Changing fluid/filter often will do nothing to alleviate a hard shift issue most of the time!
Essentially what is happening with a hard shift condition is that as the springs/shims in the accumulator get mileage on them as well as the trans itself, the springs lose tension (become softer) which extends the time between shifts. When the computer detects longer shift times either from the accumulator springs losing tension or other issues in the transmission that occur with age/mileage, the computer tells the PCS to up the line pressure which is trying to reduce the shift times between shifts with higher line pressure-Thus the trans begins to shift harsher. The trans fluid temperature component of this issue is that very high trans fluid temperature will make the accumulator springs even softer (or just aggregate other issues in the trans with age/mileage) which is why high trans fluid temperature often triggers the hard shift condition-thus where the trans coolers come in.
The following quotes are directly from the Transgo shift kit instructions:
" With 70,000 miles or more miles on the 4T65E transmissions, they often need some hard parts"-mine had 88,000 miles when the first hard shift condition existed.
"Long Shifts make a 1811 code with default to hard or missing shifts. A scan tool will show long shift adapt time. This kit will shorten the shifts without making them rough" This is true!
"EPC (PCS) solenoid-This solenoid fails with no metal contamination even on a perfectly clean low mileage transmission" Thus my comments and my personal experience that changing the fluid/filter often will not prevent this failure.
"EPC (Pressure Control Solenoid)-P1811 or PO741 and other codes and failures are most often caused by a sticking armature in the EPC solenoid" This is an electronic issues and has nothing to do with the fluid.
Hope that this helps and addressed the naysayers.
Essentially what is happening with a hard shift condition is that as the springs/shims in the accumulator get mileage on them as well as the trans itself, the springs lose tension (become softer) which extends the time between shifts. When the computer detects longer shift times either from the accumulator springs losing tension or other issues in the transmission that occur with age/mileage, the computer tells the PCS to up the line pressure which is trying to reduce the shift times between shifts with higher line pressure-Thus the trans begins to shift harsher. The trans fluid temperature component of this issue is that very high trans fluid temperature will make the accumulator springs even softer (or just aggregate other issues in the trans with age/mileage) which is why high trans fluid temperature often triggers the hard shift condition-thus where the trans coolers come in.
The following quotes are directly from the Transgo shift kit instructions:
" With 70,000 miles or more miles on the 4T65E transmissions, they often need some hard parts"-mine had 88,000 miles when the first hard shift condition existed.
"Long Shifts make a 1811 code with default to hard or missing shifts. A scan tool will show long shift adapt time. This kit will shorten the shifts without making them rough" This is true!
"EPC (PCS) solenoid-This solenoid fails with no metal contamination even on a perfectly clean low mileage transmission" Thus my comments and my personal experience that changing the fluid/filter often will not prevent this failure.
"EPC (Pressure Control Solenoid)-P1811 or PO741 and other codes and failures are most often caused by a sticking armature in the EPC solenoid" This is an electronic issues and has nothing to do with the fluid.
Hope that this helps and addressed the naysayers.
Last edited:
BillBoost37
New member
I agree you are not a transmission expert, therefore you should not be putting people down that have far more experience and understanding about the situation. Not a kick in the balls, it shows in your below quote that you don't fully understand the issues behind a long shift time and the pcm commanding max line pressure.
P1811 is the code letting you know that the pressure has been commanded to maximium by the pcm for a shift. It is not a long shift code, it is not a weak spring in the accumulator code. Many builders have found that even after putting in a new EPC and a full shift kit in the accumulator that they can still end up with a P1811 from long shift times. There are many factors that cause a long shift time. EPC not keeping up is the most common one, play in clutch pack tolerances is another. Your direct quote about the EPC having a sticking armature (mechanical, not electronic BTW) is explaining the true problem is the EPC.
The accumulator is named well. It accumulates fluid and when the springs overcome the fluid coming in, fluid will then flow behind the clutch piston faster and engage it. The amount of fluid needed (worn clutches or slop in clutch pack tolerances) can have a large impact as well. The more fluid needed overall makes the shift time longer. By shimming the accumulator, you limit it's movement and force fluid to the piston faster. This causes the shift to happen sooner, keeping the pcm from seeing a long shift time and commanding maximum pressure shifts.
By limiting the accumulator movement, you are bandaiding other issues that exist in the transmission. As well, you aren't installing the full shift kit by only dropping the pan and putting most of the kit in the accumulator. There are other parts in your transgo shift kit that require you to take the side cover off and go into the transmisson much further for a proper install.
I'll stand by a shift kit as being a fantastic bandaid for a problem that requires a good amount of labor to fix the actual issues.
P1811 is the code letting you know that the pressure has been commanded to maximium by the pcm for a shift. It is not a long shift code, it is not a weak spring in the accumulator code. Many builders have found that even after putting in a new EPC and a full shift kit in the accumulator that they can still end up with a P1811 from long shift times. There are many factors that cause a long shift time. EPC not keeping up is the most common one, play in clutch pack tolerances is another. Your direct quote about the EPC having a sticking armature (mechanical, not electronic BTW) is explaining the true problem is the EPC.
The accumulator is named well. It accumulates fluid and when the springs overcome the fluid coming in, fluid will then flow behind the clutch piston faster and engage it. The amount of fluid needed (worn clutches or slop in clutch pack tolerances) can have a large impact as well. The more fluid needed overall makes the shift time longer. By shimming the accumulator, you limit it's movement and force fluid to the piston faster. This causes the shift to happen sooner, keeping the pcm from seeing a long shift time and commanding maximum pressure shifts.
By limiting the accumulator movement, you are bandaiding other issues that exist in the transmission. As well, you aren't installing the full shift kit by only dropping the pan and putting most of the kit in the accumulator. There are other parts in your transgo shift kit that require you to take the side cover off and go into the transmisson much further for a proper install.
I'll stand by a shift kit as being a fantastic bandaid for a problem that requires a good amount of labor to fix the actual issues.
Bronco Boy
Donating Users
Assuming you mean this as a preventative measure?
I had P1811, and two fluid changes within two months did nothing.
I was only trying to make the shift kit sound like less of a magic cure. Just installing accumulator springs and spacers is only masking the issue not fixing it. I am positive it will shorten shift times just not fixing what is broke. If you do have a trans problem new fluid rarely does any good. Religious fluid changes are always good for your transmission though, its just once a problem has occurred its too late.
Sent from my SCH-R970 using Tapatalk
Sent from my SCH-R970 using Tapatalk
The sole intent of this thread started 4.5 years ago was and is to share my experience with a hard shift condition that occurred with the 4T65E transmission in my GP and to make readers aware of a fix that I used to correct the condition in the hopes that it may help others with a similar situation-nothing more, nothing less. The purpose was never to show who knows more or less about these transmissions. I have painstakingly periodically maintained and updated the progress of my particular transmission over that time to document for those that may be interested whether the "fix" has been durable or short term over that period of time. I have tried to make it clear in many posts that the Transgo shift kit may address the hard shift issue and may compensate for other wear issues in the tranny as you described above. I purposely did not mention the other components that come in the Transgo shift kit since the intent is to address my issue as simply as possible for the readers. I recently installed a full Transgo shift kit in my Ford Mustang GT AODE transmission that required a valve body removal, multiple spring changes in the valve body, check balls replacement and drilling out certain valve body passages for installation and that type of effort I was looking to avoid with the 4T65E transmission in the W body cars. Lastly, for clarification, the quotes in my post above are not from me but directly from Transgo about the 4T65E transmissions-I assume Transgo knows more about this issue than me and the reason for the Transgo quotes.
Bronco Boy
Donating Users
That's what I figured you meant. :th_thumbsup-wink:
I love all of the transmission "experts" who spout off about "the underlying problem" and band aids in that high and mighty "what a bunch of dumb amateurs" tone. I brought my 4T65E to several "experts." Each was more than happy to charge me for a full diagnostic. Not a single one was able to tell me what was wrong. Every single one told me that that I needed a rebuilt transmission installed, but not a single one could tell me why. Not a single one rebuilds these transmissions anymore because they are basically grenades and apparently none of them could tell what made the pin stay in or fall out (metaphorically speaking, of course). I am not kidding. They all order rebuilds with warranties because it's apparently the only way not to lose money on these dumb things. When they grenade again someone else is on the hook.
GM put out an early TSB on the P1811 and EPCS and later withdrew it. There is nothing in its place now because apparently even GM can't tell you all of the different kinds of things and interacting things that go wrong with these transmissions and/or with their control systems - because the problems with electronically controlled transmissions, as we know, is not always IN the transmission (or the converter).
And the P1811 is a long shift code. Max line pressure is the fail-safe put in place when the long shifts are detected so that the long shifts don't continue to burn up the clutches. What causes the extended shift times? Apparently any number of things that no one is ever able to figure out. What "cures" it? Well let's see...the $100 "band-aid" fix or the $4,000 "band-aid" temporary rebuild non-fix from the "experts." I think anyone doing battle with one of these disastrous transmissions is capable of doing the math and then making that decision themselves. There is no need to hang around talking the "right" way. The "right" way is the one that works, and I have yet to find any transmission "expert" who knows what that is on the 4T65E.
GM put out an early TSB on the P1811 and EPCS and later withdrew it. There is nothing in its place now because apparently even GM can't tell you all of the different kinds of things and interacting things that go wrong with these transmissions and/or with their control systems - because the problems with electronically controlled transmissions, as we know, is not always IN the transmission (or the converter).
And the P1811 is a long shift code. Max line pressure is the fail-safe put in place when the long shifts are detected so that the long shifts don't continue to burn up the clutches. What causes the extended shift times? Apparently any number of things that no one is ever able to figure out. What "cures" it? Well let's see...the $100 "band-aid" fix or the $4,000 "band-aid" temporary rebuild non-fix from the "experts." I think anyone doing battle with one of these disastrous transmissions is capable of doing the math and then making that decision themselves. There is no need to hang around talking the "right" way. The "right" way is the one that works, and I have yet to find any transmission "expert" who knows what that is on the 4T65E.
:th_thumbsup-wink:
Changed the fluid/filter in the 4T65E tranny today 70,000 miles later with the Transgo Shift kit and 2 18,000 GVW Long/Dana Double stack coolers in the grill (outside of the radiator cooling) after 25,000 miles since the last change and the fluid looked great with zero contaminants in the pan. As I have stated before, change the fluid/filter often (I would not go more than 40,000 miles between drain/filter intervals). The fluid color at 25,000 miles still looked red but not as red as new fluid. As I have been doing for years now, I use Walmart Supertech Dexron VI (NOT Dexron III-VI is a better fluid AND is backward compatible to Dexron III transmissions) and a WIX filter. The fluid is $4 per quart at Walmart (8.5 qts need for the change) and the Wix filter is $18=$52 for everything-cheap insurance with these transmissions. Zero hard shift issues now for 4.5 years and 70,000 miles!