LS4 Performance - 4T65E-HD Slips off the line

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.

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.

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.

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.

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.

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.