It is an 08 Supercab with the 5.4, 3.73, 58,000 miles. Truck has had NO issues until this point.



I used to be able to pull out and slip/squeel the tires (285-75-R17) if I wanted to. Now I can't, the truck just doesn't feel right.



I checked the transmission fluid (pan shows a little leakage, nothing major), it was a little low (still on the dip stick but not in the hot area). I thought that might be the problem. I added fluid, no help.



Cleaned the MAF sensor, no help......I don't think it is in the engine though, it revs fine in neutral. If I put it in D or 1st, and get on it hard from a dead stop it pulls hard to 2500rpm, then it bogs down from 2500-3500, at 3500 it takes back off pulling hard again ......Any ideas???



Oh, I did notice when I let off after revving it in neutral, I get some popping and cracking under the cab.....I didn't notice that before, maybe I overlooked it, is that normal?



Transmission fluid is good
No Codes
No engine Light
Clean MAF

 

Plugged converters? If so, you are still on emissions warranty.

Due for spark plugs at 60k, I'd do them now. Get new boots and springs for the coils when you do the plugs.

Fuel filter due every 30k unless it's in the fuel tank.

 

Also may sure parking brake not locking up. Pivots where the cable hooks up get seized and causes the shoes not to release. This may be a problem if you used your parking brake around the time this happen???

 

I would try a bottle of techron too.

Also, was this just happeneing very recently or for a long time? It could be a bad batch of gas or something as well.

 

OK,



Found part of it, maybe all.......



I forgot to mention I put a new fuel filter on it, that is not an issue.



We left on our way to the beach, I had to drive 100 miles in the WRONG direction for my daughters doctors appointment. So I drove the truck, 100 miles in, a grind started in the front end.



As we drove home the grind got louder, I did all your typical stuff....shifted into neutral, noise left. when coasting noise was gone. I pulled over, and crawled under it. I noticed the front axles were hot. One spun free the other wouldn't.



I drove it on home at this point and decided not to continue to the beach. I noticed when in 4wd the noise would quit. So I was sure it was there.



I took apart the front hub that was grinding (this axle spun free) the locker gear was ground down. So I pulled it out, I can drive the truck in 2wd for now.



I studied how the assembly worked, and realized that the hubs lock in and out. Something didn't set right with me. So I got on here and looked, I had been under the assumption this system worked as my 2000 model and all shafts turned to the diff. Not so. I noticed there was very little vacuum on this side, thought I had a hose issue.



So I got to thinking the other shaft should spin free which it wasn't. So I tore it down

and there was THE problem. There was a hole in the diaphragm, which had let water in and rusted out the housing. This side was locked in 4wd, and had been for some time.



I pulled the locker out of it for now as well. This relieved a vibration issue I had, and MPG's went from 12 up to 15on the highway. I am still not back to 17 where I once was. It is definitely a start though. The truck is still lugging in that 2500-3500 range.