I have 2 Expeditions, a '99 and a '01 both are EB 4x4 5.4's. My '99 has 230+K miles on it and runs great, however since around 110k it's always had this annoying slip and knock in the rear end when I'm on the gas going up a steep grade and it's worse when I'm towing something. I had it looked at a couple of times and no mechanic could ever figure out the problem, so 120k later I really just forgot about it. Here's where it gets interesting! I recently put a set of new tires 265/75/17 tires on the '99. A few weeks later I decided to switch wheels & tires with the ones on my '01, so that the new tires would be on my newer, nicer '01. The wheels on the two vehicles are identical.

After swapping the 2 sets, the slipping and knocking on the '99 has totally stopped and now the '01 is doing it! WHAT! It feels like the right rear, so I swapped those 2 again and tested the '01, it's still slipping! I can't figure out what could possilbly be causing this other than the wheels themselves. Anyone out ever heard of such a thing? Please help!

 

What do you mean by "it's slipping"?

 

I have a 2001 and in learning about the tires and rims found this. I have only had mine a couple of years - so just thinking out loud here - not an expert.

"The Expeditions went from 12 mm studs (19 mm socket) to 14 mm studs (21 mm socket) in late 99 or early 2000. Our 2000 has a build date of 02/2000 or 03/2000 (need to look at the tag to be sure), and has the 14 mm studs. The 2001 Navigator wheels will certainly have the 14 mm studs."

If you didn't own both of these new, is it possible that somehow they have either the wrong rims, studs or both that are not matching up. That is somehow a little bit of play or bad fit is causing the wheels to slip on the hub - as strange as that sounds. Why the symptoms reappear on the newer vehicle I can't quite come up with an idea on. But at least this is wheel related. Could a rim be cracked where you don't see it on the inside and flexing somehow?

Thanks and good luck

Mike

 

I've been searching through other post and it's sounds like what is being described in post about Control Trac Loc or Trac Lok clutch packs. It feels like a short slip and a clunk over and over all the way up the grade. It also makes this sound if the wheels try to spin (ie:wet roads, snow, etc...)

 

The lug nuts on both vehicles are identical. I also check for cracks, but could not see anything.

 

Could your tire be slipping on the rim? This is pretty far fetched but sounds like the problem is following the tire/wheel from one Expe to the other. Swap 'em back or swap side to side.

 

Again...what do you mean by "it's slipping"?

 

I swapped the right rears on Sat. It still made the same slipping and clunking noise but not as bad with the old wheel and tire in place. I'm going swap both rears and see in that does it. It does sound crazy but it does feel like the tire is slipping on the rim then catching again. I can't imagine it's not something to do with the wheels. BTW! My newer one is a 2000 not a 2001 I guess that why the wheels are identical...keep your ideas coming it's much appreciated!

 

Just a thought. Did you make sure all 4 tires are the same size? The size you mentioned 265/75/17 is not the correct size you should have a 70 series, if one is incorrect it could cause trouble with the drivetrain.

 

Just checked the tires and you were right they are 265/70/17's and they are all correct. Here's another description of what is feels like: it feels like there is a 1/2" pipe attached to the tire across the tread, again it's only while going up hills or when the wheel is trying to spin. It weird! I'm going to switch all the wheels and tires back(a job that sux when it's 90) if the problem tranfers back to my other vehicle. I'm going to replace the 2 back wheels and see what happens...Keep 'em coming guys!

 

My guess is you smoke entirely too much pot and are imagining the whole thing.

 

Sounds like the tranny rumble I had. Feels like you're going over rumble strips near a toll booth.
Have the tranny service, flushed, and have them add the Ford anti slip additive.

 

OK, I switched the wheels back between the two vehicles and of course the the slipping & clunking stopped on the 2000 and is back on the 1999. There is obviously a problem with the OEM wheels from the '99. I've had 4 different sets of tires on those wheels, so I wouldn't think it would be the tires. Have no idea what could be wrong with the wheels but I'm buying some new ones.

 

Dont buy any wheels yet! take the vehicle that the tires were originaly installed on back to where you purchased the tires and have them check them for tire or wheel runout on the balancer and that should show any imperfections in the tire or wheel.