Loud, rough thumping in drivetrain.

[gamblersgirl]

I have a 2002 AWD Explorer that has a very loud and rough thump that appears to be coming from the rear of the vehicle. It has a limited slip differential and is all time 4 wheel drive. My problem started when I was told that I could use 265 size tires on the front even though the back tires were 255s. When I " goose" my speed to around 3rd gear, it jerks then smooths out. Then you could not ask for a smoother ride. The transmission changes gears good with no slipping. Some says the 4wd is messed up others say that it is the clutches in the rear differential, while others says it could be coming from the front. I'm sorry if I am not making sense, but I am at my wits end. Any help would be greatly appreciated, Thanks in advance.

 

[manaen]

you absolutely cannot mix tire sizes on an AWD truck. You need to match those tires on all 4 wheels and your problems will probably go away. That is, if you didn't already blow the fluid coupler in the transfer case.

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 2002-2005 section. Never mix tire sizes on a 4WD or an AWD as previously stated.

 

[gamblersgirl]

I have the correct size tires on the explorer now. I knew that I wasn't suppose to have different size tires, but some guys talked me into it. The vehicle wasn't drove 500 ft with the wrong size tires, but the thumping is still there at low speeds. Smooths out when in higher gears. No binding or noises when turning the wheels. I am just wondering where should I start my troubleshooting. As I mentioned in my first post, several people have said several things that could be causing the thumping. I feel like some mechanics will take advantage because I am a lady.Thanks in advance.

 

[BrooklynBay]

Did you check the U joints?

 

[gamblersgirl]

no. It will thump and jerk violently at low speeds but after I reach third gear and higher speeds like on an interstate it runs perfect. Could that be the U joints?

 

[manaen]

yes, what happens is at high speeds they tend to quiet down, pluss the additional road noise covers up the sounds. At low speed you can really hear them. Block the wheels put the truck on Nuetral and wiggle the drive shaft by hand. There should be zero play in the u-joints you also can look at the seals and see if they are dry/cracked/rusted usually when they start making noise you will visually be able to see the damage.

Don't forget to check the front ones as well they are always spinning when you're driving...

 

[jrford]

just to be sure, there are no Switches in the dash, AWD then, some get it confused. Swtiches = 4wd CommandTrac.

To test the Viscous, do a slow figure 8 turning the steering wheel lock to lock, in the parking lot, if there is binding or the wheels skip/slid, or the truck sorta bucks, it might be the Viscous. Next test is to have someone remove the front driveshaft, if it goes away %90 it the xfr case.

Rear Diff - what is the Axle code? If its a 45 no rear clutch packs, D4 then its LSD and they might wear out. To test this - with the front driveshaft removed and it still does it, Rear Clutch packs in the diff, try drain and fill and add the Ford slip additive. . .might fix them, if not rebuild. But these also are known to cause a whine at 65mph too, so?