Truck isn't running over 40 MPH - please advise
 

Hey everyone. I'm having a major problem here.

My truck is out on the road with a friend and he said it won't go past 40 mph, but the speedometer is reading 80mph. He is reading his actual speed from the GPS unit.

I had him go to the nearest Autozone to pull the code and it comes up with a P0540, which to me shouldn't cause the truck to run like this. Am I right? The SES light is not even on at the moment.

Does anyone have any idea what is going on or what he could do to get back on the road? He is 700 miles from home and driving 40 mph isn't going to be fun. I also don't want him to mess anything up by driving it any further if he can help it. However, I really need the truck to get back to me and can't really afford to have it fixed while he is gone.

You guys would really be saving my ass by helping me out here. I'll be checking back every few minutes! Any help at all would be appreciated. Thanks.

sounds like the trans to me. if the speedo is reading 80 when only doin 40 something is sliping somewhere unless you have been having problems with the speed before this. if it was in limp mode the SES light would be on and the motor would govern out at 2000 rpms

He said everything seems to be running fine other than being governed to 40. It started up this morning and as he pulled onto the interstate, he couldn't get any faster than 40.

There haven't been any problems with the truck or transmission. The only issues with this truck have been the injectors which it eats like cereal, but the problems don't seem indicative of injector failure. I could be wrong.

Is there any way to test the transmission? It's an automatic.

Thank you for the reply. :tu:

well it should shift 4 times as your accelerating :w2: Do the rpms govern out?? It also could be the fuel filter if your lacking power.

if its the tranny the rpm will sky rocket and not move anywhere if its pulling strong then its not the tranny

I spoke with him and he confirmed the shifting was normal. The truck shifts up until it hits 40 mph and then just feels governed. He didn't count how many times it shifted, but he feels confident it shifted at least 4 times before the speed topped out. The rpms sit at about 2700 while driving at 40mph and do not govern out at 2000.

Also, the speedometer actually isn't stuck at 80, it somewhat mirrors the actual speed but at about 2x higher. When he is going 20, the speedometer reads about 40-45.

EDIT: He is currently pulling a 40ft trailer and has no noticeable lack of power.

2700 rpms at 40 mph would be like second or third gear

Hmm.. I'll tell him to pull over and count the gears as he accelerates.

Thanks so far guys. What a nightmare. :ouch:

EDIT: He counted and he is in third gear, but if he keeps pushing on the pedal the truck kicks into 4th gear likes it's in passing gear, but then downshifts again once it gets going.

Ditto the last post. 2700 RPM at 40 mph is way out of wack if the transmission is in overdrive...not possible really. Sounds like the tranny is not shifting to the upper ranges.

no tranny codes