I have used the search function and didn't find my exact problem.

This has happened 3 times now.

Hard acceleration and normal shifting and POW! AT shifts itself out of gear and into neutral. Seems to go back into 2nd gear, but will not go into any other forward gear unless I pull over, shut off the car and let it sit for a few minutes.
I say forward gears because I have not thought to check reverse when it does this.

I changed my AT fluid and filter when I got the car a year ago and changed to Mobil 1. Fluid level is correct.

My thoughts are a stuck valve body or something along those lines.

It seems to shift fine all other times.

Any thoughts on this? Or did I miss something in the search where someone has had a similar problem?

 

Do you think it may be foaming up and loosing presure?

 

I’m definitely experiencing the same thing. On three different occasions, the transmission basically shifts into neutral for no apparent reason. In all three cases the transmission reengaged after probably about 5 or 8 seconds.

Conventional wisdom around hear seems to be 1st check and double check your fluid level warmed up running in neutral. Second try some additives like Lucas Oil Treatment or the long term cleaner treatments. Third, check for vacuum leaks and Bowden cable tension. Fourth, flush and refill use upgraded ATF filter. After that it gets murky… rebuild, replace, possible try B2 bands.

I’m at stage 4 right now.


A couple of links worth reading:
https://rennlist.com/forums/928-forum/461390-help-needed-to-diagnose-4-spd-tranny-issue.html
https://rennlist.com/forums/928-forum/449831-need-help-troubleshooting-at-issues.html
https://rennlist.com/forums/928-forum/462655-m28-14-a-t-no-shift-problem.html

 

A few more good links:
https://rennlist.com/forums/928-forum/447460-automatic-trans-adjustment-write-up.html
https://rennlist.com/forums/928-forum/410690-transmission-problem-question.html
https://rennlist.com/forums/928-forum/429605-question-about-b2-piston-and-b2-band.html
https://rennlist.com/forums/928-forum/424255-looks-like-the-82-trans-needs-help-update-warning.html
https://rennlist.com/forums/928-forum/402994-auto-transmission-has-adjusting-vacuum-modulator-caused-early-upshifts.html
https://rennlist.com/forums/off-topic/387535-how-hard-is-it-to-rebuild-an-auto-trans.html

 

Brad,
I don't think its foaming up. There is no indication of that and also I don't think synthetic is prone to that.

Kurt,
Thanks for the links. I will check them out. Car was running great on Saturday and I jumped on it shifting gears up close to redline. When it was supposed to shift to 4th, it instead shifted itself out of gear with my foot all the way into it. (Chuck S.- did you know you could do that? HEHEHE) Anyway, it made my butt grab seat cushion as it went well into redline as I was coasting.

 

If there is a post by Steve Cataneo in any of those links, I would email him, or search for same.

 

Definitely will be looking for that SteveG !!!

 

not broken tranny mounts or ant thing sinister like that is it.

 

No nothing like that. I really kinda think that either one of the valves is getting stuck open or closed (I wouldn't know which) I would have thought that replacing the fluid would have corrected something like this, but maybe it was worse before I had the car. I am going to try Bill Ball's suggestion to another poster about the cleaner that is left in place. I think I'll have someone else drive the car also just to get another opinion about it's drivability. I don't believe the AT slips or anything like that, but what I'm thinking is tires spinning may be something else entirely. Does that make sense?

 

John, mine would to this off and on on the 2-3 shift.

New filter/fluids cured it.

 

Not every tranny likes every type of tranny fluid. Does your tranny shift into Neutral even if you are driving around in "3" instead of "D"?

If I had that problem on my 88 S4, you can bet that I'd swap out the current tranny fluid with *either* Porsche's OEM fluid + 24 ounces of Lucas no-slip tranny additive, or that I'd use Redline's ATF with 24 ounces of Lucas.

Is there any way to tell if your tranny fluid is overheating? Tranny cooler isn't up to snuff?

Likewise, what are the electrics on our S4 transmissions? Do we have relays or wiring harnesses that might need attention?

 

No doubt,
I am not sure if I can replicate the symptoms (actually not sure I want to run the car past redline again).
The first time it happened, I was on my way to a GTG one evening and I was running throught the gears pretty hard, but not overly so, and the bottom just dropped out (no go). Stopped, turned the car off, checked for REALLY bad things under the car, and didn't see any. Chatted with KillaV for a few minutes and mulled the options, then restarted the car and it was fine.
The second time it happened, I really don't recall the circumstances or the aggressiveness of my driving.
The third time, I came from a standing start at WOT, one shift that I recall and wound it up tight until it went out of gear and I shut it down.
If it was something I was doing that I could replicate, I could probably get a better idea of what was really going on.
Thanks for the suggestions. Working my way throught the reading now.