04lariat95

I've got an 04 f150 lariat and it just recently started vibrating but only when it shifts down from overdrive.(feels like rumble strip for 1 second). Vibration happens more often when under load. It also has a rattle/squeak when accelerating. It does not squeak on light acceleration. Also sometimes there is a big clunk when shifting gears, never from a dead stop just when shifting or after braking hard. I was thinking it might be the u joints but they look fine and don't have any play in them. Any help would be greatly appreciated.

After reading a few posts on other forums I found one that said it might be the torque converter causing the shudder/vibration when shifting? Would that cause the other issues as well?

Rick's 06

You've got a few things going on with a vibration, squeak and a clunk. You didn't mention how many miles you've got on your truck, but I'd address the easy stuff before I'd assume you've got serious issues. I'd verify the trans level is good. If you haven't ever changed the fluid and the filter, that's a good thing to do. I'd also check the diff fluid level. If you've got a two piece drive shaft it's a good idea to grease up the slip joint just behind the center bearing as well.

04lariat95

There is just over 100,000 on the truck. I checked the Trans fluid and it was fine.
Drive shaft is one single piece. Now tonight on my way home from work I had the cruise set at 60 and when I hit the top of the hills and the truck let off the throttle it felt like I was tapping the brakes lightly on and off until it accelerated again on the next hill. Rpms never changed when this happened. I will have to check diff fluid before I go to work tomorrow.

Rick's 06

Since you've got a one piece drive shaft, the clunk you mentioned is possibly a U-joint. As for your issue yesterday it makes me wonder if you're getting miss fire. Are your plugs original or have you changed them? A bad spark plug or COP has created many of the symptoms you've had for others. Hopefully someone else will join in that's had your exact problem or has better advice.

04lariat95

I had the plugs changed about 5000 miles ago. I would think a code would be thrown if there was a misfire. Would the Rpms change if there was a misfire because of the cop? What's the best way to check fluid level in the rear diff? I just took filler cap and stuck my finger in the hole. Could not feel any fluid but could only get my finger in 1/2 inch. There was a bunch of sludge on the magnet but no big chunks. Should it be full to the top?

04lariat95

I think I found the problem. The rear diff seal is leaking slowly. It only leaks when it's warm. When I checked the other day I hadn't run it yet. Couldn't tell it was leaking because of all the dust and dirt on it. The joys of living on a dirt road. I'm gonna change it this weekend, needs an oil change too, may as well do them both. Hopefully that solves the problems.

Rick's 06

Let us know if that helped. To answer your question on filling, have your truck sitting level and pump lube in the fill hole until it starts to come out the fill hole. Make sure you add 4 oz of friction modifier if you've got a limited slip.

04lariat95

Changing the rear diff oil stopped the clunk and vibration as far as I can tell. Hasn't happened since. I think I found the problem for the rattling/grinding noise too. I was reading a different forum and came across someone who explained the whole 4x4 system up front and how it works. From the sound of things I have a leak in one of my vaccum lines or the selonoid is shot. Now I just have to figure out which. The hub is trying to lock in because there isn't enough vaccum to hold it back. When I lock my 4x4 in the grinding sound goes away. I think I have it figure out but now it comes down to isolating the real cause. It was just weird that this all started happening at the same time. Thanks for the input.

Rick's 06

Sounds like you're making progress. I think you're on the right track with your 4X4. There's a thing called an IWE Solenoid that's needed to activate your 4X4. It's a known issue that they konk out. There's also another issue with the one on the passenger side that gets ruined by the AC condenser drain tube. There's a shield that Ford came out with to put over the top of it to keep it dry. Mine is a 2WD, so I'm not that familiar with this, but there's been a lot of threads on these to know they do stop working.

04lariat95

Sorry it's been a while. But I've been busy. I switched out the 4x4 selonoid and that was not the problem. Jacked the front of the truck up today and found out that the passenger side iwe will not disengage. The drivers side iwe disengages but makes a grinding noise when driving. The passenger side has a little more vaccum than the drivers side so I would think there is enough vaccum to since the drivers side disengages with less vaccum. Both sides engage when put in 4x4 but pass. Side won't disengage. Could it be possible that both wheel ends went bad at the same time? Thinking about just replacing both of them.