4T65E Trans Shift Hard, P1811 DTC

[gjhunter01]

Hi - I was on my way back from Flordia to Mich. this last weekend, when my 01 Lesabre trans started acting up about half way home. The car was loaded and running 75-80 mph when we came into stop and go traffic on a 85 deg day. Shortly after we got into the heavy traffic, I noticed the trans shifting hard and lurching forward from 1-2 and 2-3 gears. After about a mile, I pulled over, let the car cool for a half an hour and added a quart of trans oil ( it was full, but figured an extra qt. would not hurt it now). After that the car starting shifting better and now shifts like normal. I had changed the trans oil 2k before the trip. The car has 125k and I have only owned it for 2 months. Any ideas what happened and suggestions on what to expect or things I could do to extend it's life.

[BNaylor]

When the tranny fluid was changed before the trip was that a pan drop service with screen filter and ATF (Dexron-III) only or a flush? Is it still shifting normal? Also, make sure the excess ATF doesn't come out the overflow valve.

A common problem with the 4T65E autotransaxle is the pressure control solenoid (PCS) causing the hard shifting and in most cases upshifts only. If this is the case with yours then a scan with a trans capable scan tool may reveal a stored DTC of P1811 (max adapt, long shift) which would confirm the PCS is suspect.

[gjhunter01]

Thanks for the reply, I did drop the pan and changed the filter before the trip, but it was not flushed, just drained. I have been driving it to work all week and just today, Thurs. it started upshifting hard on the way home in all three shifts. How can I get the code checked, is this a dealer only scanner? If PCS is the problem, how hard is it to replace, would I need to remove the valve body?

[gjhunter01]

I just wanted to add a update. I tried half a pint of Seafoam Trans Tune in the trans. and like the label say's the hard shifting has gone away going on 3 weeks now driving 60 miles a day. I was told this might clean out the tarnish build up in the PCS. So far so good.

[BNaylor]

Sometimes the Seafoam tranny additive works so it doesn't hurt to try it. However, in most cases it is just a bandaid fix and the problem may reoccur. Also, it dilutes the ATF and you may develop other issues. If you do another pan drop you'll see your ATF will be very dark since the Seafoam did it's job so I would not run with it too long. Pic shows fluid drained from a '98 Lesabre with 140K miles that ran Seafoam for about two weeks. The ATF looked fine before that.

[imidazol97]

Originally Posted by BNaylor

. Pic shows fluid drained from a '98 Lesabre with 140K miles that ran Seafoam for about two weeks. The ATF looked fine before that.

How many times had the fluid been changed in the 98 LeSabre before that? It picked up a lot of crud using the SeaFoam!

GJhunter01 should be sure to change the filter too if SeaFoam picks up that much stuff. His filter will be partly blocked already.

[BNaylor]

Just goes to show that the Seafoam does work but I don't think it should be left in the tranny for any extended period of time. It is not an ATF conditioner.

On this particular LeSabre the first pan drop service with new Dexron III ATF and screen filter was done around 70K miles. Then around 125K miles when we had Cottman's replace the PCS solenoid. However, at around 135K miles the hard shifts and the P1811 DTC (max adapt, long shift) returned.

The LeSabre was one of my test vehicles, a total of 3 GM cars with the 4T65E autotransaxle in which I ran a GM Tech II scan tool and found the shift timing was out of specs...greater than .65 seconds causing the P1811 DTC to set and commanding high line pressure (max) and as a result the hard upshifts and in some the whining sound. This is to be expected due to tranny fair wear and tear and clutch pack material wearing away.

What we did was add the Seafoam to clean it out. Ran it for a couple of weeks and then did a pan drop with a new Filtran screen filter. The AC Delco TF304 screen filter is identical by the way and in reality a Filtran brand in Delco packaging. Then I added a a shift kit which was installed in the 1-2, 2-3 accumulator which can be accessed from underneath. Topped it all off with the new Dexron VI. Used the Wallyworld Supertech brand Dexron VI for $3.00 per quart since another fluid drain will be performed in about a month.

So far no problems to date and the shifting is excellent. Possibly a good work around for people having PCS issues or re-ocurring PCS issues. Time will tell.

[scorp102]

I went to wallmart to find a bottle of seafoam. I found a white metal can that said seafoam, but it did not say anything on the can concerning the transmission fluid. I just stated oil. Would someone be willing to post a link or a pic as to what the product looks like? Are there 2 diffrent kinds?


Thank you for your help!

[BNaylor]

Originally Posted by scorp102

I went to wallmart to find a bottle of seafoam. I found a white metal can that said seafoam, but it did not say anything on the can concerning the transmission fluid. I just stated oil. Would someone be willing to post a link or a pic as to what the product looks like? Are there 2 diffrent kinds?

Yes. One for the engine used in the gas tank or top engine cleaner and the tranny version which is used for the tranny and power steering pumps. Around $6 per can. Called Seafoam Trans Tune. See link below.

Click here

[scorp102]

Originally Posted by BNaylor

Yes. One for the engine used in the gas tank or top engine cleaner and the tranny version which is used for the tranny and power steering pumps. Around $6 per can. Called Seafoam Trans Tune. See link below.

Click here

Awesome ty very much! As I wright this post, my buick is at the trans mech doing a free diagnostic check of the trans, getting a code reading from any stored DCs. Hopefully it will be as easy as changing the PCS and a good flushing with seafoam. I will keep you posted as to what the mech says when he calls in about an hour.

Thanks again!

[scorp102]

Ok, it was as you said. The lovely P1811 code. I bought a pint of Seafoam, followed the directions, added the whole pint. And today it did great, until it started again.

So, I am assuming the has come down to changing the PCS. If I ask a mechanic to change the PCS pressure control Silinoid, how much would be a good price to go by as to what I should be charged?

Or your idea on how I should go about this.


Thank You!

[BNaylor]

Originally Posted by scorp102

Ok, it was as you said. The lovely P1811 code. I bought a pint of Seafoam, followed the directions, added the whole pint. And today it did great, until it started again.

So, I am assuming the has come down to changing the PCS. If I ask a mechanic to change the PCS pressure control Silinoid, how much would be a good price to go by as to what I should be charged?

Or your idea on how I should go about this.


Thank You!

You'd probably want to take it a specialist like a transmission shop. Cost will vary depending on where you live. Cottman's which is also AAMCO here charged around $600 with the part. But they tried awfully hard to convince us to get a rebuild which was declined.

Or you're welcome to try my work around suggestion but at your own risk. To date all I can proudly report is none of the test vehicles where this procedure was applied have any further issues.

For the accumulator shift mod I can direct you to a place on-line that sells it. If you can DIY a pan drop service then you could do this mod or have a general mechanic do it. Also, I would highly recommend switching over to the new Dexron VI with this mod. I have noted no issues. Also, I can post pics of how the accumulator looks and how the mod is done.

[scorp102]

Originally Posted by BNaylor

For the accumulator shift mod I can direct you to a place on-line that sells it. If you can DIY a pan drop service then you could do this mod or have a general mechanic do it. Also, I would highly recommend switching over to the new Dexron VI with this mod. I have noted no issues. Also, I can post pics of how the accumulator looks and how the mod is done.

That would be great if you could show some pics. I might try to do this myself.

The "new Dexron VI" is a filter? Sorry for the ignorance. Thank you for your help.

[BNaylor]

Originally Posted by scorp102

That would be great if you could show some pics. I might try to do this myself.

The "new Dexron VI" is a filter? Sorry for the ignorance. Thank you for your help.

You're welcome.

The Dexron VI is automatic transmission fluid (ATF). The older version is Dexron III. All 2006 and up GM cars now come with Dexron VI from the factory. The typical shift kits will come with a screen filter and the spacers required to improve the shifting. Also, full documentation to do the mod. The kits range from $18-$30 or higher depending on the company. If you add up the total cost of the Dexron VI and the shift kit you'll see the cost is way less than replacing the PCS solenoid. Best part it is a DIY job. Less than a $60 expenditure. The pan drain plug shown in the first pic was added to make draining easier on the next service.



8 qts Supertech brand Dexron VI, ZZP Shift Kit with screen filter and pan drain plug.



Pan removed on 4T65E autotransaxle showing screen filter and accumulator.



4T65E accumulator removed and disassembled showing 1-2, 2-3 pistons/springs

[scorp102]

You are awesome! Thank you for taking the time to show me! I will gather the parts and and get to work.

Thanks again!