Upon take off I hear and feel a "thump" or clunk. It happens once I roll about 1 foot. It is as if I am taking up slack in the drivetrain. It feels more like the rear end than the transmission. Anybody else got this? It's under warranty but I hate to go to the dealer unarmed (lack of info).
Also when I shift in reverse, I hear a metallic clank eminating from the transmission. Again, it sounds as if something is taking up slack, (It sounds like a u-joint) it will do the same as I pull forward. Then, of course, I feel the rear thump/clunk noise. BTW, it seems that I can control the rear sound by being extremely gentle on take off. Also, it will do it when I come to a stop, although it seems a bit more muffled. If you can help it would be greatly appreciated!!

 

Could be a number of things like drive line back lash or leaf spring wrap. If your still covered under warranty then take it in to the dealer but make sure you can ride with the mechanic to show them what your experiencing. Most mechanics are not good at interpreting customer descriptions of concerns and they end up saying "No Problem Found".

There is a basic spec for drive line back lash but I have never been able to get a dealership to tell me what it is. As for spring wrap my 2000 4x4 Excursion has this condition. It does not produce an audible sound but rather a feeling (rubbing or popping) that is transmitted up through the floor during accelerating from a stop and just before coming to a complete stop.

Spring wrap (as I call it) is a normal function of the leaf spring suspension during acceleration and decel. As you accelerate from a stop the vehicle's weight shifts rearwards and pushes down on the rear leaf springs. Each leaf of the spring assembly moves and slides (independently) on top of each other when under load. There are small isolators in-between each leaf to prevent metal-to-metal contact and excessive noise. I believe the suspension noise I'm hearing/feeling is coming from worn out isolators in the leaf springs. I have tried working grease in between the leafs where the isolators are located but that didn't help much other then help pin point where the problem is.

Good luck, and take note that the leaf springs are not covered under warranty or ESP because Ford believes that they are too easily subject to abuse from people driving off road or pulling over rated trailers. But if your lucky the dealer will replace them with out asking your approval and so they are free after that.

 

I own a 2000 Excursion limited (Purchased 10/99) and I am experiencing the exact same problem as you have described. I am right at the end of my warranty and would like to know if this is an actual problem. It seems that I am the only one who can feel it. Your description of the problem is like hitting the nail on the head.

 

Thank KPO for the post. You've helped me before! Hmmm...axle wrap. After I read your post I went out for a drive. It still FEELS like driveline slop. So I took a gander underneath the truck. First off, What are the half springs the point forward at the bottom of the rear leaf springs for? Do you think that under acceleration these are banging up against the main spring unit? You know, if I take off nice and easy without giving it any throttle until it is going about 3-4 mph and then gently gas it, it won't do it.(make any noise) but it will do it if I mash the brake wilst idling along. you can hear/feel it as the truck resettles back down on the springs. So, is axle wrap only a symptom of acceleration or will I experience it when I stop as, mentioned above? Also, driveshaft will turn about 1/4 inch or so while in park. That seems normal to me. What do you think?

BTW, rbrad9753 which noise do you have? The one from the rear axle area or the shift into reverse noise?

 

The noise that I hear is from the Rear end.

 

I may have found the answer...Do a search in the Super duty forum for "jerk in driveline" There is a thread with a couple of different answers form lubing the spline shaft to axle wrap problems. I think I'm gonna lube mine first. the wife and 4 kids won't appreciate me lifting it. Well, my oldest son might...
Good luck

 

Hmmm…. I would have replied sooner but I never received a response notice via e-mail. Anyway don't confuse axle wrap with spring wrap. When the axle twists from resisting the forward motion of the vehicle it causes the leaf springs to wrap. Imagine looking at the rear leaf springs from the side of the vehicle. When accelerating forward the nose of the differential housing (pinion area) tries to point up. The axle tubes are rotating counter clock wise which bends the aft part of the leaf spring down and the forward part up so the whole leaf spring looks something like a wave (sine wave). I got a point to this………. When the axle is rotated counter clock wise that one straight piece of metal (short leaf) facing forward will rotate up and contact the bottom of the leaf spring limiting the amount of axle rotation. Very similar to traction bars on hot rods with leaf spring rear ends.

As for the ½ rotation of the drive shaft, that seems excessive to me but you need to convince the dealer to address it. Although, if you have a pinion seal leak or were about to get one the dealer must re-set the ring and pinion back lash when replacing the pinion seal.

 

KPO, alright I got the correct meaning of axle wrap (thanks)now what is spring wrap?

 

I had a severe rattle in the front end of my X 2001 4x4. Took it to the dealer and they replaced the front sway bar which fixed the rattle. Now I have a thump or knock while accelarating after a complete stop and turning left or right. It sounds and feels like it is directly under the driver seat. Also when traveling over a rough road it sounds and feels like the front end is not completely solid.
Is any one out there experiencing similar problems? Any info will help.

 

There is a TSB that refers to that very problem. Oddly enough it references the front sway bar, specifically the proper torque on the nuts that secure it. Look up the TSB (use the link on the lobby page)I don't have the problem myself but when it's cold my front spring bushings squeak like a bunch of mice or worse yet, like my wife's Dodge Strange though...you just had the front bar replaced. Maybe they didn't read the TSB and assumed that you torque it the "old way". Good luck!

 

Ok, here's somethin' strange...as the first post in this thread states, I had a jerk, thump, clunk etc. in the drivetrain at take-off and when stopping. It was as if slack was being taken up. Well, it is now gone! It just disappeared...One day it's there, now it's gone. The only thing that changed was the 9 inches of snow that fell here in Mass. Saturday night. I used 4 wheel drive to get up some steep hills coming home from a Christams party. I drove it for about 45 minutes in 4H. Now the noise is gone. I don't know if these two events are linked but I think they are. Any thoughts out there? Has anyone ever had difficulties with the transfer case? Heard anything negative about it? I'm starting to think that the problem orginated there instead of the rear-end. Well, at least the noise is gone. I just hope it isn't the signal of catastophic failure. Thanks to all who posted info for me! (KPO!)

 

[updated:LAST EDITED ON 08-Jan-02 AT 06:46 PM (EST)]Howdy, thought I'd re-open this. My noise came back. I took it to the dealer today (finally) and can you believe it; Dude said he's gotta put a new driveshaft in it. Great googly-moogly!! It's about $450, I sure am glad I have an extended warranty!

I don't think that replacing the driveshaft is necessary. Well, maybe it wasn't when I first detected the noise. Seems the splines on the slip yoke were getting all FUBAR. (if needed, I can explain what this means ;-)) I imagine ensuring that these splines were greased properly would have solved the problem early...I was gonna do but never got around to it.

Sooooo, if your "X" experiences any of the symptoms that I posted above, get to your dealer or favorite mechanic or your garage and lube those splines.

 

Finally got my truck back today. New driveshaft!! It even looks different. The noise is gone!! I'll post pics of the worn driveshaft and pics of the new updated one.

 

no need for pics...I couldn't find any noticeable wear. When I took it apart everything looked brand new, grease and all. However, there was noticable play between the slip yoke and driveshaft. Anyway, I got a new one and the noise is gone. This new driveshaft has a counter/balancing weight towards the axle end that my old one didn't but other Excursions have. So maybe that had something to do with it.

Kinda bummed, I was hopin' for some dramatic, catastophic failure pics.