Chevy Cobalt Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #1 ·
Hello,

Another question about my Cobalt. I have recently been getting the infamous P1811 Maximum adaptive and long term shift transmission code about once a week and it seems to be a common issue with the 4T45E transmission my car has. Currently has 215k miles on it, fluid has always been changed on time. The cost to go in and replace a solenoid is anywhere from 300-900 depending on the shop and how long they want to diagnose it before they commit to anything and of course it has lots of miles and is probably worn quite well internally so that's not worth it without a complete rebuild.

I have a guy who doesn't work on transmissions inside but has no problem replacing one, he quoted me $600 + cost of fluid. The used transmission prices in junkyards around here are around $99-150 for one with about 65-70k miles on it. Altogether probably looking at $900 to replace it so I figure that's what I will do,

but in the mean time how bad is it for me to continue driving around with this transmission? With the code comes up it will shift hard through every gear, but still does shift. I would imagine this isn't so great on the engine/trans mounts, just not sure how much damage it will cause. I can either clear the code, or if I turn the car off for thirty seconds then it goes back to shifting perfectly for about a week. Is it okay to drive it like this until it completely fails then just swap the new one in? Is it harmful to drive it if it starts shifting on maximum pressure constantly? (if the solenoid gets really bad.) I've been told I could get another year out of it and to not spend the money until I 100% need it because it won't shift anymore eventually.

Just looking for some opinions, really.

Thanks!
 

·
Registered
Joined
·
139 Posts
I did a quick search and found that it could be an electrical issue, low fluid, or just an old transmission. If shutting it off fixes it, I am thinking low fluid or some clutch crud on the solenoid. Worst case the solenoid is going bad. Check the oil level first. What the code is, is that the trans is taking too long to upshift. So it boosts line pressure to keep from hurting the trans. If the actual solenoid needs replacing it requires removing lots of stuff and dropping the engine cradle down some to access the side cover on the trans. Once down the cover comes off and you replace the solenoid. I remember once my Mom's Oldsmobile was stalling at stops because the lockup converter solenoid was stuck. I was able to get the side cover off without too much trouble and replace it. Too bad the Cobalt is so much harder. As for advice, if you changed fluid often, it was working fine before this, I would just fix it. The bitch is getting at the side cover. There are YouTube videos showing how hard this is, but having a shop do anything is going to co$t you.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #3 ·
I did a quick search and found that it could be an electrical issue, low fluid, or just an old transmission. If shutting it off fixes it, I am thinking low fluid or some clutch crud on the solenoid. Worst case the solenoid is going bad. Check the oil level first. What the code is, is that the trans is taking too long to upshift. So it boosts line pressure to keep from hurting the trans. If the actual solenoid needs replacing it requires removing lots of stuff and dropping the engine cradle down some to access the side cover on the trans. Once down the cover comes off and you replace the solenoid. I remember once my Mom's Oldsmobile was stalling at stops because the lockup converter solenoid was stuck. I was able to get the side cover off without too much trouble and replace it. Too bad the Cobalt is so much harder. As for advice, if you changed fluid often, it was working fine before this, I would just fix it. The bitch is getting at the side cover. There are YouTube videos showing how hard this is, but having a shop do anything is going to co$t you.
Thanks for the response, fluid level is fine not low at all, I only had the car since 190k but have all the records of fluid being changed etc. I do lots of city driving for my job and I have a scan tool that can check my trans data stream, sometimes it's perfectly happy shifting all day long for two weeks without a code. Then it'll do it twice in one day, and the maax allowed shift time is .65, sometimes it's .66 or .68 which will trip the code. Check engine light never lights up though, I just know by feel and then I scan it. I can either clear the code and it will drive normally again, or I can turn the car back off and on.

Unfortunately, I have no tools of my own or anywhere I could do it. Even if I could, I'm a computer tech guy, not a car guy :( LOL. All the shops around here won't touch it without spending a couple hours diagnosing it at $100/hr. My guy will not work on replacing the solenoid but he is willing to install another transmission in it. Right now I've been driving like this for 15k miles, I think it'd be worth it to keep going and then replace it when it fails.

I found a bunch of 4T45E transmissions with low miles (40-80k) from junkyards for less then $200, my mechanic will install for $500 + cost of fluid. Seems to be a decent move, the rest of the Cobalt is in great shape. No rust (huge thing for living in PA and NJ all it's life.) Engine in great shape, suspension just about all new, been very reliable. For some reason I love this car even if it is basic.

If the transmission starts shifting at full pressure for an extended time, could that cause damage to my engine mount or any other part? Honestly, I don't mind the hard shifting because it's quick and firm I'm just scared of causing some other issue over the repeated "shocks"

Thanks again for the response and the help!
 

·
Registered
Joined
·
139 Posts
Oil is good- OK then. So it is intermittent. I hate stuff like that. It will probably go along forever and break at the worst time. The hard shifting is OK for a short while like clearing the code and it re-sets itself. But you don't want to drive around shifting hard for very long. A transmission that has been modified to shift hard has had other work done to accompany the changes. And that is usually done to a fresh performance rebuild, not a high mileage one. It won't hurt motor mounts but rather the internals. So if you are unable to do the work then you are at the mercy of those that can. The guy who will swap them for you seems like a good idea. As you said, it may be just the solenoid, or it can also be an old worn out transmission. Replacing with a known good one would solve several problems. I say known good one because you would hate to do all that work and end up with a slipping worse transmission.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #5 ·
Oil is good- OK then. So it is intermittent. I hate stuff like that. It will probably go along forever and break at the worst time. The hard shifting is OK for a short while like clearing the code and it re-sets itself. But you don't want to drive around shifting hard for very long. A transmission that has been modified to shift hard has had other work done to accompany the changes. And that is usually done to a fresh performance rebuild, not a high mileage one. It won't hurt motor mounts but rather the internals. So if you are unable to do the work then you are at the mercy of those that can. The guy who will swap them for you seems like a good idea. As you said, it may be just the solenoid, or it can also be an old worn out transmission. Replacing with a known good one would solve several problems. I say known good one because you would hate to do all that work and end up with a slipping worse transmission.
Thank you, yeah I'll replace it with a known good one when the time comes. I have roadside assistance with free towing to 100 miles so I'm covered there. So, if the only thing the harsh shifting causes is problems to the transmission internals I guess it wouldn't matter driving like that then? Just drive, it dies and I get it towed and replaced. Seem like a plan LOL.

I'm going to keep clearing the code but I assume as the solenoid gets worse it'll probably come right back after clearing so that's the point I'll be driving around with it harsh shifting all day long.
 

·
Registered
Joined
·
139 Posts
The problem is that you assume the solenoid is the culprit. The computer sends a signal to the pressure control solenoid, but it doesn't know what happens after that. Only a shorted or disconnected wire will set a trouble code. It could be worn out clutch discs slipping too. According to the FSM it could be the solenoid, the wiring or connector could be loose, the fluid too old, the fluid level, (but you are good to go there), worn clutch discs, and a few other internal things. Remember, the trans has a flexible window of how long it should take to up-shift. Once you exceed the parameters, it assumes the trans is slipping. Then the trans control module switches to maximum pressure. That covers up the slipping and you get the harsh shifting. That is why a shop would want to test a lot so they can pinpoint the exact issue. On old transmissions, the vacuum modulator and throttle cable would sense vehicle load and adjust the pressure. Then if it was damaged and slipped, you knew it. Myself I would try and diagnose it better and then fix it. My friends would say drive it until it explodes then deal with it. I'm sure the right answer is somewhere in between.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #7 ·
The problem is that you assume the solenoid is the culprit. The computer sends a signal to the pressure control solenoid, but it doesn't know what happens after that. Only a shorted or disconnected wire will set a trouble code. It could be worn out clutch discs slipping too. According to the FSM it could be the solenoid, the wiring or connector could be loose, the fluid too old, the fluid level, (but you are good to go there), worn clutch discs, and a few other internal things. Remember, the trans has a flexible window of how long it should take to up-shift. Once you exceed the parameters, it assumes the trans is slipping. Then the trans control module switches to maximum pressure. That covers up the slipping and you get the harsh shifting. That is why a shop would want to test a lot so they can pinpoint the exact issue. On old transmissions, the vacuum modulator and throttle cable would sense vehicle load and adjust the pressure. Then if it was damaged and slipped, you knew it. Myself I would try and diagnose it better and then fix it. My friends would say drive it until it explodes then deal with it. I'm sure the right answer is somewhere in between.
Oh okay I got you, well based on the fact sometimes it takes a week or two to start shifting harsh again and set the code, that's what is making me believe it's the solenoid instead of clutch discs or anything because in my mind that would make it happen much more consistently. Obviously I'm not sure about that, that's why I came to you guys the experts.

At this point, it would be just about the same cost to replace solenoid or anything else so I'm just going to drive it until it's dead then get another to go into it.

I do have a good scan tool the can read transmission data, when the code comes up it's always like .68 or .72 the max is .65 before it starts adjusting the pressure. I drove for an hour yesterday and had the scan tool reading all the TAP cells, everything was perfectly in spec all across the board, shifting like a new transmission the whole time. No code, nothing. Going up and down the valley(lots of shifting) but anyways that's about it.

Thanks for your help!
 

·
Registered
Joined
·
19 Posts
Hello,

Another question about my Cobalt. I have recently been getting the infamous P1811 Maximum adaptive and long term shift transmission code about once a week and it seems to be a common issue with the 4T45E transmission my car has. Currently has 215k miles on it, fluid has always been changed on time. The cost to go in and replace a solenoid is anywhere from 300-900 depending on the shop and how long they want to diagnose it before they commit to anything and of course it has lots of miles and is probably worn quite well internally so that's not worth it without a complete rebuild.

I have a guy who doesn't work on transmissions inside but has no problem replacing one, he quoted me $600 + cost of fluid. The used transmission prices in junkyards around here are around $99-150 for one with about 65-70k miles on it. Altogether probably looking at $900 to replace it so I figure that's what I will do,

but in the mean time how bad is it for me to continue driving around with this transmission? With the code comes up it will shift hard through every gear, but still does shift. I would imagine this isn't so great on the engine/trans mounts, just not sure how much damage it will cause. I can either clear the code, or if I turn the car off for thirty seconds then it goes back to shifting perfectly for about a week. Is it okay to drive it like this until it completely fails then just swap the new one in? Is it harmful to drive it if it starts shifting on maximum pressure constantly? (if the solenoid gets really bad.) I've been told I could get another year out of it and to not spend the money until I 100% need it because it won't shift anymore eventually.

Just looking for some opinions, really.

Thanks!
By a brand
Hello,

Another question about my Cobalt. I have recently been getting the infamous P1811 Maximum adaptive and long term shift transmission code about once a week and it seems to be a common issue with the 4T45E transmission my car has. Currently has 215k miles on it, fluid has always been changed on time. The cost to go in and replace a solenoid is anywhere from 300-900 depending on the shop and how long they want to diagnose it before they commit to anything and of course it has lots of miles and is probably worn quite well internally so that's not worth it without a complete rebuild.

I have a guy who doesn't work on transmissions inside but has no problem replacing one, he quoted me $600 + cost of fluid. The used transmission prices in junkyards around here are around $99-150 for one with about 65-70k miles on it. Altogether probably looking at $900 to replace it so I figure that's what I will do,

but in the mean time how bad is it for me to continue driving around with this transmission? With the code comes up it will shift hard through every gear, but still does shift. I would imagine this isn't so great on the engine/trans mounts, just not sure how much damage it will cause. I can either clear the code, or if I turn the car off for thirty seconds then it goes back to shifting perfectly for about a week. Is it okay to drive it like this until it completely fails then just swap the new one in? Is it harmful to drive it if it starts shifting on maximum pressure constantly? (if the solenoid gets really bad.) I've been told I could get another year out of it and to not spend the money until I 100% need it because it won't shift anymore eventually.

Just looking for some opinions, really.

Thanks!
Take it to a different mechanic and ask them to clean and fix all engine compartment grounds
 
1 - 8 of 8 Posts
Top