Well about a week ago I posted on here and never got any answer so I went around the internets looking for people with similar problems. Found very few people with no answers. So lets see if maybe I can explain the problem a little better. In all reality it feels like a parachute opened up in the back and is trying to slow me down at times. Its like a strain on the truck but the truck accelerates and all that just like it always does. It didnt start until like 3 days after i changed the rear differential cover. I put all new fluid in it and an additive for the locking rear. Well it was great for the first 3 days but on my way home i was driving in a huge rainstorm and all the sudden it felt like i was driving through a huge puddle of water. That resistance you get well it stayed the whole time no matter what gear im in. If i shift it into neutral the drag seems to go away some. Its not always dragging either just at certain times. Theres no squealing or noises. Its quiet as can be. Im just real confused. I dont know if its the diff oil because it is a different kind then the original. I switched to synthetic instead of regular gear lube same weight as what the tag on the rear called for. Im just wondering if the clutches in the rear diff are dragging because the additive i put in for the rear locking system isnt compatible with synthetic. Any help would be appreciated Oh by the way its not the break system at least i dont think. The front i did a year ago and the back i did about a month ago. So pretty new all the way around. Thanks again!

 

Does it feel like the EBPV is coming on

 

Do you have the limited slip rear end? do you know if the fluid you put in didn't have the additive already added? Maybe you put in too much additive.

 

This is a better explanation than your last post thread, which you had plenty of "options" and thoughts for answers...your description in that one seemed more like a pull to one side than this description.

This description sounds more like a possible sticking EBPV, you could try unplugging it to see if it goes away, the plug is tough to get to but is located at the front of the turbo pedestal. Possible causes could be from a clogged EBPS or tube.

 

I'm sure many on here have more experience with these trucks than I do, but I would start with the last thing I did and back track.

I would jack the rear end up so both wheels were off the ground and try spinning them buy hand. If they are they a really hard to spin you somewhat have narrowed it down. Could you have used the wrong oil for the rear end?

I would start there.

 

Synthetic oil is whats suppost to be in these rear ends. So you didn't mess up there. And even if the oil has additive for the limited slip you are suppost to add to it to. The manufacturer will tell you that. Thats what amsoil said. If your brakes aren't getting hot, they aren't the problem. Feel the rims when you stop. EPBV on the turbo would cause this but it usually is on and don't open just because you step on the pedal. You are right
its a rare problem. I would jack up the rear end and spin the tires like said above. If they spin freely, or lets say without really hard force they are good. If they don't pull the drive shaft and try again. Let us know what you find and go from there.
Chet

 

I doubt this is your issue but I have experienced what u are talking about a couple times. Almost like a heavy trailer behind the truck. In my case, it had a little harmonic to it as well. No noise but like a feel in the truck that was different.

Mine is always proceeded by wife driving my truck....She is a parking brake fanatic. The only problem is that she is not strong enough to engage the brake to the point that it will also make the light come on. SO it barely drags.

Are your parking brakes dragging?

 

Do you have a EGT guage? If so, if your EBPV is sticking your EGTs will be out of check (way high)

 

I have a few questions/thoughts:

1. Exactly what brand of synthetic fluid did you use in the rear diff? Royal Purple? Red Line? .....?
2. The friction modifier: again, brand details, but also, how much did you add?
3. Brakes.
a. When was the last time you completely flushed the entire system?
b. Have you checked/adjusted the parking brake?
c. Did you clean and grease the caliper slide pins when you did the brakes?
4. Transmission - I just had to replace the plug on the end of the harness that attaches to the passenger side of the transmission. Check and make sure that there isn't water in that plug/connection. It's a common problem.

EBPV may very well be your issue, but brakes are always worth checking over.

 

Ok maybe that's what is wrong with my fx4. Cant help to feel a drag when I acc in a turn I feel a little vibration and it feels like maybe the tire slipping but no tire screech and it just doesn't feel right. I did a diff service about a year ago and thought it was just the tires.

And here is another one when I'm backing up the driveway and put a little power to it to get over the hump I get a loud " clank" someone said it was in the suspention. Checked it out cant locate noise must be in the rear end btw Ive got new universals on drive shaft.

 

Yeah Ill jack it up. Last time I did that they wouldnt spin at all the were locked up tight. The limited slip diff likes to lock up sometimes when I stop and shut off the truck. No its the same oil the tags on the rear diff called for. 75W -140.

Cant be my EBPV because its not making the noise like air escaping an compressor fitting.
1- Valvoline synthetic W75-140
2- It was a NAPA brand additive forget exactly what it was. Ill have to look it up when i go to NAPA agian
3- About a year ago. FLushed it when i blew a line.
Adjusted brake when i replaced rear brake system. Has an exposed E brake line where the tire rubbed off the outter coating.
Yes its all greased up.
4 I have a man transmission dont think i have that plug.

Ill still check that EBPV valve.

 

Ah, you are on to something here. If your rears are in the air you should be able to spin them. Was this before or after the oil change?

When was the last time you checked your parking brake? The lining can delaminate from the shoe and cause what you are describing.

 

I think it is your rear brakes or ebrake. These trucks are known for having sticky slide pins. That is where I would start looking because with the rear wheels off the ground and you don't have it in gear they should turn without alot of force.

 

Upon reading through the various suggestions and problem description, what I believe is a key component that needs to be focused on is the variability of the problem... "at times", "not always", etc.

How is this variability going to be explained by ...

1) EBPV... this is typically a "working correctly" or "not working" issue... unless perhaps it is the EBPV sensor, and not a plugged EBPV line. Then again, the abscene of the "jet engine noise" would suggest that this is not the problem.

2) Wrong fluid/not enough friction modifier/too much friction modifier... this again would be an "all the time scenario, would it not?

3) Badly adjusted parking brake/loose lining... again, all the time, right, if this is the issue?

4) Sticking slide pin.... now here is something that can be variable... sticks sometimes, slides sometimes, right?

One more thought I have is....
I assume that your new differential cover has a higher volume than your original??? Please verify. If it is a larger volume, could you have potentially put in too little or too much fluid? Too much fluid causes foaming which is really bad on the gears, and too little fluid will prevent adequate lubrication... either will seriously increase your differential temperature which would not make either scenario any better.

 

Well my rear diff cover is stock cover from AutoZone so it shouldn't be any higher capacity. I filled it until it started dumping out the overflow and then sealed it. I was told to fill it till it spilled out the overflow andcap it off. Is that to much?