avexhype

2009 Mustang GT
52k Miles, Auto, 3.73's, JLT, Brenspeed Tune

Hey guys,

Ever since I did all my upgrades at the same time at 38k miles, I've noticed that there's an issue right after the car shifts from 2nd to 3rd gear, in WOT only, no other gear ever, and never during part throttle or cruising.

It's like it tries to go into 4th gear right after shifting into 3rd, then suddenly downshifts again back into 3rd to finish the gear. It jerks you pretty good, almost feels like Traction Control kicked in or you hit the rev limiter/spark or fuel gets cut for a second.

This problem is seen in the video's below, in all 3 tunes. Having the TC button on or off does not make a difference. I already talked to Brenspeed and they sent me a few revisions and we tried to troubleshoot, but the problem persists. At first I thought this was an issue with the tranny and 3rd gear going out, but I had it checked out by Ford since I'm under warranty and they did a tranny service/flush/whatever needed, they found no problems. On the factory tune/stock airbox I don't really notice it all - too much shift pressure maybe?

Check out the video:

91 Tune, TC On:
http://s983.photobucket.com/user/ave...39dd0.mp4.html

87 Tune, TC On:
http://s983.photobucket.com/user/ave...e6f9b.mp4.html

91 Tune, TC Off:
http://s983.photobucket.com/user/ave...3bbc4.mp4.html

91 Tune, TC On:
http://s983.photobucket.com/user/ave...dbb34.mp4.html

What could it be? Throttle sensor? 3rd gear band servo motor? Too much pressure/tranny is weak and can't handle it? I'm extremely frustrated.

greytung06gt

if it happens stock not very noticeable. the tunes magnify the problem is in the factory control box ECM computer. tunes make it bigger!

808muscle

Almost seems like the computer is confused at what to do after shifting to third. So are you are saying with the stock tune the problem is still there just not as bad?

avexhype

Yeah, I'd go as far as saying that on the stock tune it only does that 15% of the time and when it does, it's hardly noticeable.

The tune definitely magnifies the issue

2010candyred

My cars doing the same thing did you ever find a fix