Driveline Humming/Rumble

[V8BoatBuilder]

Ok... first some background:

As most of you know, I completely gutted the old AWD t-case and drivehsafts from my 97 Mountaineer, it came stock with an AWD system. I replaced it with the 2spd legit transfer case from an Expedition (same as F150), the rear drivehsaft from a Navigator, and the front driveshaft from an F150. All junkyard parts.

I put new u-joints in the shafts (2 rear, 2 front), and everything worked awesome. I drove the truck down to Delaware and back, plus around MA. The swap has over 1500 miles and is working well. However, I've only had the front driveshaft in for the last 500 miles of that. Coming back from the DWE show, I started to get a humming/rumble from the front on coasting and decelleration from 30-75mph (I don't usually drive faster, so it's unknown if the humming stops). Press the gas, and the humming stops.

The t-case is in 2wd, but the Mountaineer does not have hub lockouts, so the front shaft is always spinning at highway speeds. The truck didn't exhibit these symptoms before.

I removed the front shaft at a rest area, and the humming went away. The u-joints are all properly greased with Mobil 1 synthetic, and turn smooth.

Thoughts?

 

[boominXplorer]

See if there is any runout on the front t-case flange. How is the front diffy gear oil? I know the pinion bearings are not the best up front.

 

[Cali' Explorer]

Aaron-
I had this exact same thing happen to me when my front Driveshaft CV/U-Joint went out. But seeing as how you have 2 U-Joints in the front D-Shaft and no CV, that makes no sense.

What about the automatic sensing? Doesn't the 4406 sense wheel sleep and engage the front end when needed? If this is the case, could it be sensing wheel slip when there is none and engaging the front driveshaft anyways?

 

[V8BoatBuilder]

Aaron-
I had this exact same thing happen to me when my front Driveshaft CV/U-Joint went out. But seeing as how you have 2 U-Joints in the front D-Shaft and no CV, that makes no sense.

Elaborate on your noise please, because the principles being a u-joint and a CV are similar.

What about the automatic sensing? Doesn't the 4406 sense wheel sleep and engage the front end when needed? If this is the case, could it be sensing wheel slip when there is none and engaging the front driveshaft anyways?

It does indeed, but I preformed the "brown wire mod" which disconnects the front clutch for 2wd.

 

[Cali' Explorer]

Elaborate on your noise please, because the principles being a u-joint and a CV are similar.

Well, its been a while, but heres the best way I can explain it. We have a section of highway out here that is ribbed for water runoff, so you basically get a mild hum the whole time you are driving it. The hum/sound I heard sounded like I was driving over that same section despite the fact that I was no longer driving over that section. Almost like my tires were out of balance or something. Then I started noticing that the front end felt like it was fighting me (not wanting to turn, steering wheel vibrating slightly, etc...). Almost like when you go over a grated metal bridge, not quite as bad, but imagine going over one at 65 MPH and that's what I had.

Then, it started almost catching and the X would lurch to the site on the freeway. Luckily I was almost home, but as I pulled off the freeway, I started hearing a solid clicking/clunking sound. Limped home and took it to Ford the next day, said it was the from Driveshaft. I think the said specifically it was the CV Joint (which you don't have) and that it was just loose, but because it was driven loose on the freeway, it was toast and got replaced (under warranty thank god). Once replaced, all was good.