We've got 2 excusions and one started acting up today it's an 01 xlt 4x4 with the 5.4 v8 and on the way home today it shifted throught the gears and up to 3rd and at about 40 mph it feels like its applying the brakes by it self and slows down till about 20mph then it goes fine until you 40mph again. I can run it throught 1st and 2nd with no problems and it will go past 40mph with it in 2nd just fine it only does it when in drive I'm really at a total loss of what could be causing this I checked the Trans plugs they were nice and clean inside and out fluid looks good and doesn't really have a burnt smell I'm wondering if maybe the abs system could be causing this? Not sure if they have a governor I've never hit one anyway, but if so could the speed sensor be acting up?Any help would be awesome

 

Could be many different things. Bad powertrain module, the valve body in the trans saying bye bye, and yes, I could see the ABS doing that, but very unlikely given the way they are designed.

The primary thing I would go after first is the trans valve body or a torque converter not working right.

But it is just a guess......

Speed limiter is set by the computer. somewhere around 95 MPH. It canbe removed with a custom tune and a tuner.

 

Thanks for the reply, ya the abs doing that sounded like a long shot. I'm not sure what the drivetrain moduler is I'll have to look that one up, and the valve body in the Trans is that something you can get while the pans off if so I'll give it a try and change it myself what's it gonna hurt at this point haha. As far as the torque converter I dont know much about thos what are some ways to tell there going bad?

 

Probably not the trans, you would know if it acted in that manner. Bad shifting, burnt oil, overheating, etc. Something wrong with the brakes probably. Quickly shift to neutral next time it starts to do it. I have a feeling you will get to the bottom of this very soon.

 

Check your brake rotors with a laser thermometer to see if the heat increases after driving. I just put a transmission in my uncle's dually for doing that very thing. Felt like the brakes were applied while driving. Fluid was ok and not burned or tarnished, but had a torque converter and pump failure which caused the issue. I hope that is not the problem, just sharing a recent experience.

 

Thanks for the info putting in in N was gonna be the next thing I tried tonight, although she does have just over 180k on her so it might have just been her time to fail I'm not looking foward to that bill tho any input on inturnals I should upgrade if I end up having to go that route?

 

Upgrading would be a personal preference. I have never heard of an auto trans acting like that but the converters have changed a lot since I used to rebuild them, hopefully Mark K. will chime in to shed some light on that. While upgrading is an option you might still be stuck with a bad truck still. Let's hope it is nothing serious.

 

That is exactly how I figured out the problem with the dually. When the truck started to slow, I shifted into neutral and the truck released.