I've had this happen a few times and it's starting to worry me a bit now. A couple times (maybe 5-6) I've come off from a stoplight at part to maybe half throttle and the transmission has slipped. At first it was bad because I didnt even notice. (too quiet) The car very slowly crawled forward before I noticed it should be moving faster, than it would slam into gear. Now that I'm aware of the issue I've been able to let up on the throttle, then slowly ease back into it with no issues or slamming into gear.

I read somewhere that to make the Super shift as smooth as it does, the line pressure is limited. I know enough about automatic transmission to know that higher line pressure would cause a noticeable shift with less "possible wear." But I've noticed that if I sit at a light for a longer period of time the torque converter must go to full stall and shed all the fluid because I can lift my foot off the brake and the car will not creep forward unless I give it throttle. I'm wondering if the pressure is very low during this situation and when I hit the throttle and it slips, its trying to build pressure up but can't quick enough. I have to add, I drive like a grandma.

I'd like to fix the slipping before I cause some real damage. I'm thinking a fluid and filter change is in order since I have 71K miles on it. But is this a common problem? If so is it at all related to the line pressure? If so I'd like to increase the line pressure while I'm doing the Trans Service. Any feedback is greatly appreciated.

 

add a shift kit and tranny cooler too

 

suggest a filter/fluid change and get hp tuners or a tune from someone and get them to increase the line pressures. I dunno if a shift kit would help you or not.

 

I'm tuned, with fresh fluid/filter, and a shift kit. It does it every fall/winter. I read on TEP's site that it's the forward apply band (don't quote me on that) wearing.

 

When you have this problem, have you tried putting it first to see if it will move? If so, then Alabama Guy is correct, it's the forward apply band. You'll need a complete rebuild if that's the case. My second tranny died this way, and the dealer put in a GM reman, which is also a piece of crap.

Agreed. What sucks is, this is the last thing to come out of the trans when you teardown, so it can't be even fixed without a full rebuild.

 

My trans (4t65e) would slip off the line at a light (intermittently). I did not have any check engine light come on, this is what I did; (07 Impala LT 3.9L 89K mi's 4t65e)

Keep in mind my problem may not be the same as yours but what I did was a few trans pan drops on our 4t65e. the first drop I cleaned the oem (weak) magnet that sits in the corner past that little hump line, and reinstalled pan with a new reusable gasket and put new dex vi fluid in it. Well it has seemed to help about half of what I was experiencing with the intermittent slip then catch.
next I decided maybe the trans needs a good cleaning so I poured half bottle of seafoam trans in it and drove around about 50 to 75 miles like that after a while the slip got less and less...
So I dropped the pan again because it was still a small intermittent slip. after I pulled the pan off I inspected the magnet and it was about as saturated as the first time I cleaned it with the previous pan drop. (about 50-75 miles earlier) so I cleaned it again and went to ebay and ordered a 2" neodymium magnet. (claiming 22lb. pull). installed that at the corner area where or right past the hump line. and poured new fluid, same thing - a small intermittent slip, so I added some seafoam trans into the mix.
While driving it around I noticed the slip that doesn't happen all the time got shorter and shorter now I don't even notice a slip and I'm convinced that the neo magnet I installed is doing a fine job along with the cleaner that is bringing the grey little gunk to the magnet. by the way I installed the weak factory magnet on the filter somewhat close to the pickup area so I have 2 magnets with the pan magnet being a 2" round flat (very strong neodymium) magnet. I will keep you all updated!

 

My car has just started to do this as well. My trans fluid as well as the filter, were both changed at about 58K and I'm at 61k now. For me it's just a paint in the butt. I've been saving for a TEP trans so I won't have this one much longer, I just don't want it to crap out on me till then since it is my DD. Does anyone know of any ways to prolong the life of the transmission? I only need it to last maybe 2-4 more months.

 

You don't need a new transmission, run seafoam trans through it and install a neodymium magnet on the pan, you can get this strong magnet off of ebay. this is what I did and mine is shifting good now.
I'm pretty sure the TCC and PCS are getting sludged with fine debri because the magnet thats most likely in your transmission is a cheap *** small piece of fridge magnet that saturates very quickly due to the weakness of it's magnetic pull. I went to ebay and typed "neodymium magnet" and ordered a 2" flat round magnet thats in the trans now, after the second pan drop i did showed the saturated original magnet thats when I decided to get a very strong one. mine is a 22lb pull which is very strong. so just run cleaner through it and put a good magnet in the pan along with the original, put the original weak magnet somewhere on the filter. after I did this mine started acting very good. it slowly diminished the slip than catch until it now seems totally gone.
Is your problem slip then catch when taking off?

 

Yea, it normally happens when my car is cold and at a complete stop. I'll stop and get on the gas and it will rev like it's in neutral and then slam into gear. as the OP said, now that I know it's doing this I let off the gas till it gets into gear and then start driving. I was planning on getting a TEP trans way before this started happening anyway. I plan to do things like LS2 or LS6 intake swap, headers, LS2 TB and LS7 Maf, etc. So because I plan on doing that I want to get a beefed up trans like the TEP trans. I just need this one to last me till I can get my new trans lol

 

My SS is doing the exact same man(see sig). I hate to break it to ya but it's done nothing but got worse and I'm tuned with fresh fluid/filter and a trans cooler. TEP trans on the way.

 

yeah your sensors sound like they have some fine wear sludge building up on them, and you dont get a trouble code or check engine light? I would just run some seafoam through and put the extra neodymium magnet in it. mine was doing the same thing and the cheap magnet that gm put in there was saturated again after I ran the cleaner through and it started acting right finally.

 

No I'm not getting any codes or anything. My car shifts perfectly fine except when it's cold and does that. Any other time it shifts so smooth you don't feel it. I will do all that for this one. Hopefully that will help at least for a few more months.

 

Yeah the cheap stock little lightweight fridge magnet gm decided to install from factory are pretty weak and saturate quick. I believe once they are saturated the other fine wear particles go to the PCS and/or TCC. I'm pretty positive anyone with this problem will easily resolve it with a pan drop, new fluid, new magnet (neodymium-doesn't really matter the shape of the neo magnet too much as long as it sits on the pan without hitting anything) you can also stick the cheap magnet that was in the pan from factory in a different area like suggested in other forums "on the filter". and pour half pint of seafoam cleaner in it and drive it around for a while before a second pan drop or you can suck the dex vi and seafoam cleaner mix out with a pump and refill it although a second pan drop is recommended.

 

So I reckon this may be 3 years late for you but this is for those who it applies to now.

This is a little long BTW but good info with symptoms.

Unfortunately you will have to do a rebuild on the transmission.
I own a 2004 Pontiac Grand Prix GTP with the 4T65E-HD. My car was acting as described in the thread. Cold start trans slip slam into first gear and it got worse over time to slamming into gear after reving it up to about 2500 RPM. After taking it to a transmission shop and them just saying "transmission is bad" and me saying "no ****" I tried the fluid swap method several times and it helped a little but eventually I lost reverse. I decided to do a rebuild (rebuild kit cost roughly 200) I found out my input apply clutches were completely gone, straight metal no material, then I found that a seal for reverse was busted (when put in reverse you can hear it act like its passing fluid to it but nothing happens) after the rebuild and replacing all the solenoids and sensors inside I had a new tranny. From what alabama guy said forward band (slips on cold start but works fine in manual, once car is warm it works no matter what) is corect. Now there are multiple youtube vids in case you rebuild. I was able to rebuild in 2.5 days with taking my time (got off work on friday and started, teardown clutches and seals sat. and together on sun and was driving it to work on mon). All I had was cinder blocks, a 1.5 ton jack, wood, and a cheap tool kit. had to buy a 33mm socket for CV axle and torque screw drivers for trans side cover but all in all it was a success. you dont need to pull the engine or anything just drop the driver side suspension sorta, and there you go. So in summary, slip on engaging and slam into gear no matter what you select the shifter, input apply clutch, if engine light is on its the clutch pack or a sensor inside the transmission dirty or telling you something is bad (read codes to see like torque converter clutch solenoid or shift solenoid a). if slips off cold start and gets better when its warmed up, forward band, sensor, or torque converter is starting to fail... which is the least likely. if in reverse you hear fluid going through like its suppose to but no reverse then its a busted reverse seal which requires a rebuild. One more thing I noticed is when driving it suddenly has no forward or reverse but shut it off and it fixes for a little bit and does it again after any given distance (a mile or 10 feet) do a fluid swap and change the filter but keep in mind its usually a sign that something internal is going bad like clutches. keep an eye on the car and see what it does. if the engine light is showing before/after the swap its telling you something else is going on as well. As for the dreaded P1811 code is just in summery telling you the car is in "safe" mode, max adapt and long shift. it will usually follow other codes like p0742 which could be caused by the fluid swap loosening up trash and it gets stuck in the solenoid or the clutches are actually failing. Best thing no matter what even just a sensor i find it best to do a full rebuild. yeah you can patch it up for a bit but keep in mind it will only do more wear and headaches. I will attach pics of the input apply clutches as described (I know the teeth look like some are missing but that is the way they are made, look at the friction material) and the reverse seal.

 

Keep in mind to those who plan on beefing up their engine while running the 4T65E-HD or non HD, GM put the bare minimal torque rating tranny in the cars. I believe the max torque rating is somewhere around 280 ftlbs which the LS5 that came out and you see impalas, GTX, and such with that is right at the spec mark if not a bit more which is why so many SS impalas and GTX potiacs have tranny issues. As a daily grandma driver the 4t is an okay tranny but overall its a very weak one. if you plan on doing an engine swap to something more powerful I suggest an aftermarket tranny or rebuild it and add stronger internals to it.

 

One more thing and I hate to do it but go to this site
http://tripleedgeperformance.com/4T6...-Problems.html

It is very detailed and helpful. I have searched for months for help with the tranny and this is just about the only site that is of any use.

 

I'm at a crossroads with my transmission. I have this classic slip and bang hopefully it won't fail in The next couple years. Do I throw in a 1300$ transmission and send the ls4 down the road and build on to better cars like a Vette or do I throw in a TEP transmission and just do some bolt ons. I'm not sure, RWD and manual sounds fun but isn't practical for where I live

 

Im in the same boat man. I love my gxp and it still runs awesome with 183K on it. I wanted to dod delete, cam, and ls6 manifold. But then I need a trans that can hold. Im just going to leave it the way it is and buy a TA ws6.

 

What really is pisses me off is that I only have 86k miles and it has a list of problems. I'll probably end up trading it in where I got it from, it's an awful but great car haha. But I need a manual transmission again that's for sure. Did you ever find a fix for the abs and traction control light always on?