Hey, it's my first time, ok? My 03 250 SD 2wd, at, longbed 5.4, does this thump thing. When you start moving forward slowly, sometimes there's a small but solid thump--you hear it and can even feel it. The first time, you think you ran over something, or something hit you. I'm wondering if it's something in the heating/ventilating system, vacuum operated and kicking something open, or closed. Any thoughts? Thanx

 

There have been reports of a thump from the hvac system. Try starting your truck and wait a minute and see if it does it if you don't move. That would rule out a drivetrain issue.

 

Hi...
No, it doesn't do it sitting still. The noise, btw, comes from the right footwell area. I wonder if when accelerating away the vacuum/pressure changes in the hvac system are changing enough to do some action or other. Still confused, but that's nothing new.........

 

Tom,
I have a 2000 CC 4x4 w/ a 5.4L have noticed the same thing about a week ago. I've only had the rig for a few months so I'm trying to figure everything out about it as all my previous rigs have been GM's. (No I don't plan on any flames cause I don't mind as long as it is made in the good ole' USA!) My first thought is fuel in the taking moving around as we had the same thing occur w/ my wife's minivan. Unfortunately it occurs whether it is a full or near empty tank. For clarification, do you notice it when taking off, even slowly, and fell/hear it after no more than 5 feet of forward movement? I'm also thinking it may be tranny related as it seems as if the tranny takes a bit before it grabs (automatic). Anyhow, I'll be floowing this thread to find the thoughts of others. I've only been here since I bought my truck but this group of people really know their stuff. Nothing like a big group of real users to come through for you!

Regards,
Jeff

 

Thanx Jeff...
I wouldn't say only 5 feet of travel, but not much more. The dealer, with whom I have only a passing relationship (I buy 'em there, come back when it's time for a new one), can't say much on the phone, but you can't blame them for not being able to make a long-distance diagnosis. I'll be looking around, as well.

 

This is a very common problem...


Here is a link to the fix..

http://www.eurekaboy.com/f250/slipjoint.htm

 

Thanx, I'll have a look.

 

Ditto, one more thing to do next weekend along with all my fluid changes.

 

It is common to get a thump out of the AC door a few seconds after starting. I know you said it doesn't do it when sitting still, but the AC thing only happens when you start the truck with the AC on (and then not everytime). Try turning the AC off when you shut off the truck.

Matt

 

My '02 does the same thing, thought I had major problem under truck, but noticed the same noise after startup sitting still. Was the same noise I heard while moving. Figured out it's same noise for sure coming from heater box control. Hope that helps? If I let it warm up before driving it will make the noise. If I take off right away it will do it in a few feet.

 

I saw that thread but mine must be the spline. Happens every time after coming from a stop.

 

Hey...
I went under the truck today at work, and the driveshaft is fine. I'm really leaning toward this hvac box door thump--it really isn't road related, but happening in or around the cab. Thanx for all the suggestions.........

 

TomB,

When you say the driveshaft is fine, do you mean that you didn't see any visual signs of a problem?

As you probably know, the slipjoint is covered by the rubber boot, and I doubt that you would be able to move the driveshaft by hand and feel the play in it.

If you only feel the "thump" when you start moving from a stop, then I am 99% sure this is your problem. If it was HVAC related, you would feel and hear it even when the truck was sitting still.

Besides, it's one of the cheapest "fixes" you can do, and really doesn't require alot of effort (other than dropping the drive shaft)

Just don't drop it with the truck on an incline, without the wheels chocked, and without the emergency brake on!!!!

 

I wouldn't believe it until I did the fix either. It works.

 

My 2003 250 SD 7.3 PSD does the same thing but not everytime...your telling me that greasing the spline will cure this??? I find that hard to believe but if I can get a few more people to say it works it will move to the top of my things to do list