Hi all...been lurking for a while for lots of little issues I've had. Got one now that I can't pin down. I recently replaced all my plugs and coils about a week before this issue appeared...but I'm not sure thats causing this issue. Symptoms are:

Noticed a few weeks ago that when I'd accellerate from standing still, the rear end feels like it slips for a split second and then engages...Doesn't do it anytime except for when taking off. This has continued...Also if I hold the brake and give it a little gas, once I release the gas the truck does a sort of slipping/popping back down even though I'm pressing the brake...feels like the rear end gets pressure and slips back down...if that makes sense.

I also noticed a strange split second high pitch sound coming from the engine when I'd release the gas pedal while driving...this has gotten worse and now this sound appears when when releasing the pedal and then after I shut the engine down it will do it, one to three times. Strange...I've opened the hood and listened to it after shuttting it off and it's echoing through the bay, so I have no idea where its coming from.

Lastly, I'm hearing a gurgling sound coming from the left side of the engine (when looking at it) right around the coil packs...

I've replaced the tranny fluid and filter, thinking that may be the source of the slipping with no change. Any ideas would be helpful. Thanks

2003 Fx4 SuperCrew 4.6

 

If the rear end were slipping, it would be really noisy all the time. It's more likely your transmission is slipping. How many miles are on it?

No ideas on your noises except the A/C will continue to hiss after shut off as well as cooling system noises.

 

the surge maybe that the emergency brake pads are binding or have come loose from their mount. (This is only if you have rear disc brakes). Do you have correct amount of gear oil in the rear diff? Do you have a limited slip rear axle?, if so, then you might just need new gear oil and friction modifier.

the gurgling...maybe signs that your heater core is giving signs of age & giving clues that it going to give up somewhere up the road. ( mine does this too, more on short trips of less then 5 miles).

the hissing after shut down, I agree is probably the A/c system depressurizing

 

Thanks for the replies! It has 186k on it, but the transmission does seem to work perfectly during shifting. Maybe it is the A/C making the hissing...I'll check it without. I was thinking that maybe a coil pack might be loosening? I'm not sure.

I do have rear disk brakes, I'll check that. I also thought of checking the fluid in the diff and I'm not sure about if the axle is a limited slip. This is my first time dealing with any drive train stuff aft of the tranny. I'd hate to have to take it in and pay someone to tell me whats up...I do everything myself and hope to figure this out. Thanks again.

 

Its the transmission, i have an 02 f-150 2wd super-cab 8' bed, 237,000 miles on it. its the 1st gear band slipping, mines been doing it for over 110,000 miles. still going. i just got use to tapping the gas from a stop till it picks up the slack. it also makes the noise under hard acceleration when it shifts.
After re-reading your post. sounds like a vacuum leak. All of of it. if this started after you did the plugs and packs. PCV valve, cracked line. mines also a 4.6. there is a main vacuum block at the back of the intake. (this came to me after a while, was a long time ago) when i did my number 4 plug and pack at about 80,000. i somehow cracked that hose. It was harder to fix than changing the plugs and packs.

 

Any high pitched (not a belt) sounds when releasing the gas? Or after shutting the truck off?

 

No, not when releasing i get it accelerating. After re-reading your post. sounds like a vacuum leak. All of of it. if this started after you did the plugs and packs. PCV valve, cracked line maybe. mines also a 4.6. there is a main vacuum block at the back of the intake. (this came to me after a while, was a long time ago) when i did my number 4 plug and pack at about 80,000. i somehow cracked that hose. It was harder to fix than changing the plugs and packs. i didn't get the noise, but i was running worse than before i tuned it.

 

sounds like a misfire to me

what brand plugs and coils did you use?

 

Thanks for the replys! As an update, the clunk when accelerating from a stop was the drive shaft where it meets up with the transfer case. I greased it with the Ford grease, it worked like a champ. I located it by mounting a GoPro to video under the truck while I did a test drive on it, I could see it popping back and forth.

The high pitched sound is still present...No idea...and the truck has now popped a code for Cyl 1 misfire...Changed the coil, it came back. Pulled the plug, it did have some oil in the threads but it looked like it hasnt really gotten down in the cyl. Planning on doing a compression check on it next and maybe checking the fuel injector.

 

Just an update for historical purposes. The high pitched sound was my head gasket...it had blown, the truck began to overheat one day, I found all of my coolant was gone...just gone lol...Obviously had leaked into the cylinder and that was causing the misfire. The engine had 190k on it, I decided to replace the entire motor with a Jasper remanufactured long block. I did the work myself, it cost about 4k all together and it's been over 10k without a hitch. New engine is awesome.