Just wondering if anybody has any ideas as to why this happened. I was messing with a an older 05-06 Mustang Shelby today. Going about 30mph in S mode. Bumped the shifter to drop into 1st and nailed it. Pulled hard and then felt the power disappear, RPM's were at 6700 and car didn't shift. Let off the gas and it shifted fine. I've never had this happen before, maybe the computer just had a brain fart?? I dont know but it is shifting fine now. I'll keep an eye on it, hopefully nothing. Anyways thank God for rev limiters!! BTW Shelby didn't stand a chance on the second pull!!

How many miles? Have you done the tranny service? How long have you had the TCU tune? Issues before? Did they increase your rev limiter?

Maybe the TCU tune?

Check Intercooler pump

78K, fluid was changed at 50K. TCU tune has been on for over a year, never done it before, rev limiter is increased to 6800. Only thing I can think is that things happened too quickly for the TCU to react and it missed the shift. Dropping into 1st at 30mph puts revs at about 4K I think then stabbing the throttle up to redline in under a sec especially with a bit of wheelspin. Was thinking about getting fluid changed in the near future. Maybe I will have that done and have them check to TCU for any codes too.

????

I had the exact thing happen to me several times last year. It then progressed into having to pull over, shut the car off, restart and it would be fine. Finally manifested as part of the drum assembly inside the transmission. Basically what happens is over time the assembly can develop wear and allow a little play front to back inside the case. When the play starts to get excessive, the speed sensor in the transmission tells the TCU that the internal transmission speed doesn't match the wheel speed, this info tells the TCU to go into limp mode and exactly what you described occurs. I took mine into the dealer because any wheelspin at all would send me into limp mode. They scratched their heads and finally had the master tech based in Chicago tell them the drum scenario and that it was irreparable and to replace the transmission. They did exactly that and now the car is beast again. I even partnered with Jerry who tried very, very diligently to help, but it ended up being this internal issue. Sorry to be the bearer of bad news but sounds like it may be transmission time.
Regards

Right, maybe I should check my tire pressure too???

Hmm, I hope this is not the case, but if so at least I will make use out of my warranty, lol!! So for the warranty company has made out like a bandit as I have not used it once!! Were there codes stored in the TCU when this was happening? If so do you know what they were, I'm gonna bring it down to Speedriven shortly and have him check codes with Star. BTW it didn't seem like TCU was in limp mode as it shifted fine once I let my foot off the gas. Tested it again after posting this and shifted great, 1st gear S mode stomped on it, wheels spinning, shifted crisply it 6700 into 2nd

Believe me brother I truly hope it isn't the case as well, but this is exactly what mine started doing last year. I only drive the car 6 months out of the year so it it happened in a short span mileage wise. I have a warranty as well and they covered it so I'm sure you'll be ok if its the worst case scenario. I read your OP and I had deja vu really bad. I mean this is word for word how mine started. As far as codes, they had speed mismatch codes, they didn't tell me exact code names or numbers. We tried everything before doing the trans too, multiple conductor plates, TCU itself, the works, but it was the drum assembly in the end. Keep us posted and best of luck to you!

Be prepared for your warranty to laugh at your claim because of your mods.

Yea, I know. Hopefully can get the claim done if needed without them coming to take a look to inspect the car.

all codes will be store in the TCU. You can connect the car to DAS and read them. Most like it will say RPM signal implausible etc etc

I dont know if it is the same issue but, when the car is running really efficient i.e. if its cool outside, i will hit it and if it kicks into 1st gear it will pull so hard that is will pause for about 1-2 seconds @ 6700 RPM then finally shift.

Your problem is probably the rev limiter is set to close to your shift points. You either need to lower your shift points or raise the rev limiter.

That happened to my car all the time at the track on the old TCU tune.

This. The TCU initiates a shift point at a certain RPM however still needs x amount of time to execute. The more mods we have and especially in first gear the faster the engine will rev thus passing the expected shift point. Might need to ask the programmer to initiate the shift sooner in first.

Thanks, this is exactly what I was thinking may have happened. Just didn't seem like limp mode. I will get the codes checked and have Speedriven look at the tune. Hopefully this is the problem and not the trans itself!!

+1 for the TCU tune, my C32 used to do it all the time with the raised shift points. Probably similar issue.

I'm not sure I really understand the extended shift points in these cars either. Most of us have far more power in the midrange than at the tippy top of our gear.

My car seems to do something similar went wot 1st or 2nd and the car seems like it hit the rev limiter kinda bounces you back had to let off then resume happened two times last 2 months? car does not have tcu tune but has other mods.