Car seems sluggish until it hits around 40 to 50 mph. Slipping tranny, jumpy. How do I fix this? 2001 Ford Mustang V6

 

Welcome to the forums!

You didn't mention what kind of transmission, so... Could be a few things:

For the manual:
1 - Time for a new clutch and/or throwout and/or clutch master and/or slave and/or clutch fluid and/or clutch cable adjustment and/or clutch cable replacement and/or pivot and/or clutch fork (if any of those are applicable, then those are the things to look at, as I'm unsure what you got goin' on.) That's it, nothing else. The gears in the manual don't slip, they break if you're really *really* unlucky. It's all about that clutch situation.

For the automatic:
1 - Low fluid.
2 - Filter's clogged/old fluid/both.
3 - Downshift linkage needs adjustment possibly, but I'm kinda thinkin' not...?
4 - You can maybe try some 'transmission honey' that's approved for use in your transmission. Something like the old standard TransX like we'd throw into the C4s or C6s or Cruise-O-Matics or FMX's of olden days. Since the AOD is supposedly an offshoot of the.. um... C4? I think that's right... anyway throw that TransX/equivalent honey in there and see if that works.
5 - Transmission's shot, time for a rebuild/replacement.

The below is not a sponsor, suggestion or any of that. Just an example so you know what I'm speakin' about regarding that transmission honey:
https://shop.advanceautoparts.com/p/...2916/7120029-p
You drain out (however you wanna do that) the appropriate amount of fluid from the transmission (assuming it's full in the first place) and then pour this stuff in. Let it do it's thing and it may rejuvenate things and prevent a 'now' trip to the transmission shop. Oh, it's probably still gonna get there, just puttin' it off a bit is all.

Probably none of that is much of what you wanna hear, but yeah... that's kinda it, I'm thinkin'. Of course if I'm wrong, great! What it is, peoples/OP? You tell me?

I still hope it helps.

 

I think it's a t5. It's a stock 01 sn95 mustang V6 3.8L

 

Definitely clutch related then, so that transmission is gettin' pulled and just replace it all, I'd say. New clutch and flywheel, pilot bearing, throwout bearing, pivot bolt for the fork. Maybe a new cable while I'm there. (I went and looked and it seems the Sn95 is still using the cable/fork system.) Should fix ya up.

The T5 is a stout transmission. Nothin' to worry on that thing. Might change out the fluid while I was there, as certainly draining the transmission will make it just a little lighter than if it has fluid in it, and hey, fresh fluid.