Thread: 4T65E Hard Shift-Solution

Originally Posted by Blacknight02GT

Hello, i have had this exact same trans problem occurring only in warm weather or once with 5 ppl in my car on a stop and go drive. Once you shut the car off and turn it back on its fine again. My problem first started occurring after I had my trans fluid flushed and filter replaced at 55k miles. It only did it on hot days in long drive times, until late September I got my coolant flushed and the weather got cooler and the problem seemed to disappear until now with the warm weather i noticed it acting up again.. after going all winter with NO PROBLEM. I'm so frustrated with this. Do you guys think my car could have the same problem? Would this shift kit help it stop? How much have u driven in hot weather with this "fix"? UGHH I dont' know what to do about this. I'm pissed.

Please read my comments above for your answer in my other responses. Your problem sounds like just a bad PCS solenoid since the hard shift occurrence is so infrequent and only when the trans gets really hot. If there are no other issues with the trans, then a rebuild is definitely not required-you do not need a trans rebuild for a bad PCS solenoid. My reasoning for this thread! I have been driving recently in 70-80 degree weather with no issues. Install a shift kit (I used ZZP's-it does not make the transmission shift harsh-follow the instructions-you can tailor the shift firmness) and install the biggest double stack cooler (not a traditional tube and fin cooler) by passing the radiator cooling lines. I used a Long brand cooler (2 - 18,000 GVW coolers). I should have just used a single 1 1/2inch wide Long 28,000 GVW cooler but tried to go the cheapo route first. In really hot weather in stop and go traffic the A/C fans run continuosly and keeps the fluid plenty cool. So far, this fix has worked-my first hard shift issue occurred in Oct 2008 and here we are in May 2010 and the trans works perfectly-no rebuild in its future. I don't race with the car, just drive in normally occassionally getting on it!

jbamonte

Would it be possible to post some pictures of the cooler and where you mounted it. Did you have to get alot of special tubing to plumb this in, I think you also stated you used Dexron VI, doesn't the owners manual specify Dexron III? My car has over 110000 miles on it, bought it used with 80000 miles on it and don't know when the fluid had been changed, the trany started doing exactly what you descibed just now and I checked the fluid it looked kind of bad but didn't really smell burnt, I sucked out as much as I could and repalced the fluid with new dexron III and still have the same problem. Is the Dexron fluid VI thicker and will help this problem? I'm thinking of doing what you sugested to see if it would help, would this problem be partly caused by a bad filter or really dirty filter.

Originally Posted by jbiebs

jbamonte

Would it be possible to post some pictures of the cooler and where you mounted it. Did you have to get alot of special tubing to plumb this in, I think you also stated you used Dexron VI, doesn't the owners manual specify Dexron III? My car has over 110000 miles on it, bought it used with 80000 miles on it and don't know when the fluid had been changed, the trany started doing exactly what you descibed just now and I checked the fluid it looked kind of bad but didn't really smell burnt, I sucked out as much as I could and repalced the fluid with new dexron III and still have the same problem. Is the Dexron fluid VI thicker and will help this problem? I'm thinking of doing what you sugested to see if it would help, would this problem be partly caused by a bad filter or really dirty filter.

I will try to post some pictures of the cooler setup this coming weekend since I have to replace my A/C condenser and receiver dryer due to a leak but getting pictures will be tough since the space is very limited and pictures would have to come from underneath once the plastic cover is removed. The coolers are mounted vertically on each sider of the front air intakes in the nose using all the hardware that came with them. No special lines needed since I just cut the 2 factory cooler lines with a tube cutter bypassed them and clamped the rubber hoses from the coolers on those lines.

Dexron VI is just a better fluid than Dexron III and can be used to replace in the earlier cars where Dexron III is specified but I don't think it will solve the problem if you have a bad PCS solenoid.

Hope that helps!!

Correct me if I'm wrong but doesn't this cooling procedure seem to cure the bad PCS problem?

Obviously, replacing the PCS solenoid is the correct way to remedy the issue but the costs involved are very high. Cooling the fluid down for the way high temperature it runs from the factory and speeding up the shifts with the shift kit will cure the problem if your tranny does not have any other issues-it is NOT a bandaid on the problem. What you are doing is replacing electronic control of the pump pressure and replacing it with mechanical control like in the old days before electronic everything. Since very high tranny fluid temperature effects a bad PCS solenoid, lower the fluid temperature helps that PCS isssue as well and just as important will do wonders for extending the life of these tranny's. I should have put a cooler on the 4T65E years ago but figured GM would know after 40 years of running tranny cooler that transimission fluid should be kept as cool as possible for proper operation, not as hot as possible for proper operation-wrong!

Will winter weather cause a problem with the trany not getting warm enough uphere in North Dakota it can get to -30F

Originally Posted by jbiebs

Will winter weather cause a problem with the trany not getting warm enough uphere in North Dakota it can get to -30F

That's a good question since -30 is real cold! I would run one big cooler after the fluid is cooled by the radiator rather than running the cooler (s) just with airflow since you get real frigid temperature alone with the shift kit. You must also run the shift kit since the kit speeds up the times between shifts and the computer will not go into fail safe mode from the slower shifts which occurs during very high tranny fluid temperatures-probably a combination of weak springs with age in the accumulator and the high temperature malfunctioning the PCS solenoid. That may work for you but certainly worth a try. The cooler after the radiator will lower the fluid temperature in the summer from a high let say of 210-220 to around 180 degrees and during the winter the fluid may drop to 130-140 which would be fine. i would give it a go if they rest of the tranny is OK.Hope that helps!

What a timely thread!! My 2000 GT recently began hard-shifting after 185,000 miles and I am looking at buying another tranny. Now I will be investigating this solution.

bsorenson, keep in mind that this issue is a pretty specific one that has to do with the pcm entering a mode where it commands full line pressure after it has detected too much slipping - or, maybe, the pressure control solenoid messes up and provides full pressure when it isn't supposed to. It operates almost on a toggle switch type of logic where the hard shifting starts, and if you shut the car down and turn it back on it goes back to being perfectly normal.

In your case with 185K on the trans you might just be seeing an actual need for a rebuild. As the clutches wear and slip more the line pressure will be increased to compensate and you'll get hard shifts.

I wouldn't necessarily say that the shift kit wouldn't help, and its not that expensive to try. So you could always give it a shot.

Does the P1811 code indicate that this the pcm is the issue? I am throwing that code. Further, the problem did not exist one day and then does the next.

First, just be aware than I am no expert on transmissions. I do get the basic logic of how they work, and have read up a lot on this problem by now.

In short, no the 1811 code doesn't actually tell you anything about whether the PCS is working or not. Its description in code lists is "Max Adapt Long Shift." Basically, the car's computer keeps track of how long it takes to get from one gear to the next. (I believe it is supposed to be .65 seconds or less). If the computer detects too many long shifts (> .65 sec) it will send full transmission fluid pressure into the shifts. When it does this you feel it as a hard shift / bump shift.

The reason it does this is actually to protect the transmission. All smooth shifts (whether in an auto or manual trans) involve momentary clutch slipping between gears. The more slip the smoother the shift. But the more slip the more wear and heat are created. The full line pressure / hard shifting basically eliminates slip - helps avoid completely burning up clutches and overheating the trans.

Now, the PCS enters the picture because it is the thing that controls the line pressure for the shifts. Every time you drive the line pressure is going up and down in response to what all else is going on - e.g. at light throttle line pressure tends to be lower. The computer is watching what all the car is doing and is commanding the PCS to give a certain amount of line pressure for each shift.

Apparently it is the case that many of these PCSs had problems - they get gunked up and don't work right anymore, and/or get shorted out by high trans temps. If the PCS does get messed up you can get the hard shifts for various reasons.

But, it is also the case that the PCS might be doing exactly what it is supposed to. If your trans is worn and there is too much slipping between gears the computer will see it, it will command full line pressure, the PCS will respond the way it should, and the 1811 code will get set.

The only way that you can really find out is by having a highly experienced transmission tech put the car on a very fancy scanner where all of the inputs and outputs and pressures and etc. can be monitored. But even that doesn't always seem to help.

If the computer does detect a PCS malfunction, that does have its own code - P0746 (PCS Performance). I just don't know what kinds of conditions or events trigger that code.

Hope that helps.

very useful information. thankyou sir

Originally Posted by jhs3eva

First, just be aware than I am no expert on transmissions. I do get the basic logic of how they work, and have read up a lot on this problem by now.

In short, no the 1811 code doesn't actually tell you anything about whether the PCS is working or not. Its description in code lists is "Max Adapt Long Shift." Basically, the car's computer keeps track of how long it takes to get from one gear to the next. (I believe it is supposed to be .65 seconds or less). If the computer detects too many long shifts (> .65 sec) it will send full transmission fluid pressure into the shifts. When it does this you feel it as a hard shift / bump shift.

The reason it does this is actually to protect the transmission. All smooth shifts (whether in an auto or manual trans) involve momentary clutch slipping between gears. The more slip the smoother the shift. But the more slip the more wear and heat are created. The full line pressure / hard shifting basically eliminates slip - helps avoid completely burning up clutches and overheating the trans.

Now, the PCS enters the picture because it is the thing that controls the line pressure for the shifts. Every time you drive the line pressure is going up and down in response to what all else is going on - e.g. at light throttle line pressure tends to be lower. The computer is watching what all the car is doing and is commanding the PCS to give a certain amount of line pressure for each shift.

Apparently it is the case that many of these PCSs had problems - they get gunked up and don't work right anymore, and/or get shorted out by high trans temps. If the PCS does get messed up you can get the hard shifts for various reasons.

But, it is also the case that the PCS might be doing exactly what it is supposed to. If your trans is worn and there is too much slipping between gears the computer will see it, it will command full line pressure, the PCS will respond the way it should, and the 1811 code will get set.

The only way that you can really find out is by having a highly experienced transmission tech put the car on a very fancy scanner where all of the inputs and outputs and pressures and etc. can be monitored. But even that doesn't always seem to help.

If the computer does detect a PCS malfunction, that does have its own code - P0746 (PCS Performance). I just don't know what kinds of conditions or events trigger that code.

Hope that helps.

Great explanation! It is nice to see thorough explanations to issues and solutions that involve more than just 2 sentence explanations loaded with sarcassim. BTW-Just passed 7,000 miles on my transmission with the coolers and shift kit with no hard shifts. Thanx.

jbamonte, when you pulled your accumulator what kind of shape was the accumulator gasket in? How about the piston seals? Did that kit come with new gasket and piston seals or were the old ones perfectly good to reuse?

The Transgo shift kit doesn't come with these and I don't know if I need them.

For anyone else looking at this job, there is akit by Thrasher what comes with new gasket and piston seals. I'm kind of wishing I ordered that one... (but it is also $90.)

Originally Posted by jhs3eva

jbamonte, when you pulled your accumulator what kind of shape was the accumulator gasket in? How about the piston seals? Did that kit come with new gasket and piston seals or were the old ones perfectly good to reuse?

The Transgo shift kit doesn't come with these and I don't know if I need them.

For anyone else looking at this job, there is akit by Thrasher what comes with new gasket and piston seals. I'm kind of wishing I ordered that one... (but it is also $90.)

\\


I installed the shift kit about a year ago and the accumulator gasket was perfectly reusable. I carefully separated the two halves of the accumulator once the bolts were out, it easily came apart with the gasket in perfect shape and very reusable. The piston seals on mine were perfect, no issues. My gaskets were in excellent shape but as I have said before, my transmssion was never abused since new in 2001 and the fluid was changed at 45,000 miles (way too long BTW!), 65,000, 93,000, and again at 95/96,000 chasing the hard shift problem before I came across my solution.

jbamonte

Did you happen to get any Pictures of this setup with the cooler?