Well.. having a problem with my truck. Figured I'd describe it and see if anyone had any thoughts.

Truck has 102k miles. I had been having a bad vibration in 2wd when driving.. but it came from the front end. But on the fly, if you switched into 4high, the noise and vibration went away and the truck was quiet and smooth. Switch back into 2wd, and it was loud and full of vibration again.

I thought it was the CV joint on the front driveshaft, so I replaced the front driveshaft. Problem was still there but not as severe. However, it got worse again. This time around, the pinion yoke on the front diff has excessive side to side play, in and out play, and the pinion has too much rotational play. The pinion nut was NOT loose.

Diff fluid is gray and metallic, about the color of the truck.. Dark Shadow Gray.

Everyone concur that it sounds like the front diff pinion bearings are shot, and possibly even ring/pinion wear? Would be replacing this myself if I don't just off the truck for an F150.

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2006 Ranger FX4 Level 2

Probably a U joint?

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2004 4.0 4x4 5spd xlt with 175k 4.10 axles, extended cab, cranked t-bars (not maxed), painted black interior, 32x11.5x15 bfg a/t and procomp steel rims
60/40 mod with a shorty console

Sounds like pinion bearing problems. No idea on damage/wear to the ring + pinion (I don't know how much slop there is in it, nor how long you drove it like this) and there's probably a good chance metal shavings are floating around in the oil.

IMO, you've got two options: a) pull the axle, disassemble and see what needs to be done to make it right or, b) JY a low mile front axle, which may look real good after reading your OP. Look on car-part.com for prices and make the decision.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000

Thanks for the replies. I also think it is a bad pinion bearing.

Not sure yet what I'm going to do. If I rebuild it, it is getting the Torsen T2 limited slip installed while its out. Not sure I want to put any more money in the truck. An F150 is looking pretty tempting right now.

I have searched some for a low mileage front diff. We'll see.

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2006 Ranger FX4 Level 2