Automatic Transmission - occasional gear loss?

Hey guys new to the site, First off I have a 99 T/A, A4, 131,000 miles, all stock.
The story:
I was headed to the track friday night (95 mile trip...one way) and the car was running great as I was merging from hwy 65 to hwy 60 on the on ramp I kinda floored it to get ahead of traffic but to my suprise my car revved to about 5K and then the trans kicked in resulting in a tire spinning sideways adventure of epic proportion in front of a 18 wheeler, almost hit a concrete barrier and needless to say freaked me out a little, but I was able to keep a leash on it and avoid an accident. Then I continued on my way looking for something to wipe with lol, the car took off in first shifted firmly into second and when it hit third it was like it was in nuetral, so I stopped and put it in park, said a few profanities, put it back in gear and all was well continued to the track with no problems, probably should not have ran it but.....it was a long trip. Car ran great at the track (13.51 @101mph 1/4) and it ran great coming home except for when I come to a stop, then it will take off in first, second, and once agian no third until i stop and put it in park or nuetral, then it will continue fine shifting through all gears fine, you can even floor it and it takes off like a rocket not slipping one bit. I do not have a check engine light for codes to read. I am wondering if the trans filter could be plugged possibly because my stepdad use to own it and I traded my truck for it, but while he owned it I know it was not serviced....at all :( I did some research and found some info on a 3-4 shift problems requiring a rebuild, but since it happens on and off I am hesitant to jump to that conclusion, but anyways any input would be appreciated and thanks for any help provided.

First verify the fluid level is at top of crosshatch with the trans warm running in park

It is possible that the fluid level is low. But I would think that the symptom would have been exagerated at the race track launching at WOT. So I'm going to doubt that one. And to answer your question, if the filter were clogged it would exhibit issues in all gears not just the 2/3 shift. As a side note, we usually like to see our units ran about half to 3/4 of a quart high. The pans on the F-body 60e's are awfully shallow.

If it hasn't been serviced I would suggest removing the pan and inspecting it for debris. I suspect that your input sprag slipped then grabbed when you whacked the throttle. It's one of the weaker components in these units that's often overlooked when diagnosing issues like you've experienced. If you plan on driving it like you described in your post then I would recommend having your transmission rebuilt to a high performance level. It can only take so much in stock trim and if it is an older unit that's never been gone through then I would suggest that there are some worn if not burnt clutches in it. I could be wrong, but that's a pretty typical scenario....

g

The first thing I checked was the Trans fluid, I placed it in nuetral with the e-brake on and checked it and it was exactly full and did not smell burnt and didnt even have any discoloration to it (everything checked out fine) the car only does it when you drive it easy, if you take off (1/2-3/4 throttle) it shifts nice and firm every gear no problems at all, even at highway speeds it will cruise just fine and downshift and accelerate without slipping at all. I could drive it all day around town with no problems as long as I give it at least 1/2 throttle when I take off and it shifts into third, which can be difficult with traffic and the 5.0 lurking around, anyways I am letting it cool down now and I am going to pull the pan and will report back with my findings, thanks for the info guys I really do appreciate it, also with the severe lack of service could it be possible that one of the shift solenoids are gummed up (sticking?) and when I try to drive it easy the fluid pressure isn't enough to allow the solenoid to operate fully (change gear)? just thinking out loud:) sorry lol

Well everything looked normal no debri and the magnet(?) had some buildup, cleaned everything up and put it back together so IDK. My brother is going to do a trans flush, probably won't fix anything (but it's free) I found a rebuilt 4L60E transmission for $550 w/ a 6 month warranty probably end up going that route if the flush and filter don't help, if anyone wants throw in your .02.....it will help pay for my tranny! lol

Well I changed the filter.....now it wont shift to 3rd at all >:( so thanks for all the help now its going up for sale because I am frustrated, need an everyday driver and cant afford to fix what ever is wrong with it, thanks anyways guys.

Buying a new car is not cheaper then fixing a very simple transmission.

I understand that, it's not that I really want to get rid of it, but I haven't got $550 bucks for a transmission. I would love to keep it but don't have the funds simple as that.

Why don't you call me Monday? There may be some options you are not aware of.

g

Alright, thanks

well Got pissed and floored it it hit the rev limiter and took off now it shift every gear fine, wonder if it was plugged up and just needed the cobbs blowed out of it? IDK but it seems to run fine now.