Front end grinding - ONLY while coasting in 4x4 high

[mthompson]

Hey guys,

It's been snowing on and off here in WI lately. I had to use 4x4 high twice in the last week on the highway; speeds around 30-40 mph. I noticed that when I would let off the accelerator, I would get a grinding noise (metal on metal whir) in the front end while coasting. Press the accelerator, noise goes away. It is less pronounced at lower speeds...so I just get passed the crappy parts on my drive, then switch to 2wd and white knuckle it slowly. (would rather do that then wreck something in the drive train)

I did a bit of interweb searching, but couldn't find much. A lot of "it's brakes", "it's u-joints", "it's CV boots" with no solutions....but it only happens in 4x4 high, while coasting. So those responses don't make sense to me. I have been driving with my hubs locked for 2 months now, no noise in 2wd with them locked.

What do you guys suppose? Could it be pinion bearings? How would I check those? (no experience there)

I'm thinking, I'll change my front differential fluid and strain for filings. I have search for a specific 6.4L tutorial, to no avail. Any of you guys do this before? Got pics or suggestions on the procedure?

Thanks,

[drewactual]

sounds like a bad carrier bearing..

this is not our differential, but everything else is consistent... D represents the carrier bearing cap, and E represents the shims:



those bearings, while loaded with torque, tend to align properly.. when coasting, they tend to wallow.. wallow enough, and they wear- allowing more room to wallow, hence the bearing needs to be replaced.. wallow it enough to release a shim, the shim is now free floating around in the differential- which brings the expression "monkey wrench in the gears" to mind..

differentials are $$expensive$$ to replace, or work on.. I'd rec you open it up most ricky-tick and figure out what the issue is..



edited to add: here is a good start on servicing/rebuilding a differential... http://www.pirate4x4.com/tech/billavista/Gear_Setup/ ... note: hopefully you'll catch it quick enough that a full rebuild isn't required.. the thought of rebuilding one gives me instant heepeejeepees and doing it will cause lasting nightmares. seriously... that job sucks..

[mthompson]

I don't see the diagram in the post? But, I figure it's from that link.

I've never worked on one of these before. Would I be able to tell by just checking the "wobble" like a normal bearing? Currently everything in 4x4 high works fine. But I don't want to use it because of the noise and possible more damage.

Is there a way to tell what axle is in my truck? Are they all Dana 60s? I like doing things myself, because then I know they are done right (I can't seem to find a good, honest mechanic around here). I know enough about working on vehicles that I know when people are blowing smoke or don't fix things properly....so I just do it myself most times. This seems to be a bit over my head right now, but I would still like to do it if it's not terrible.

I will do some research while a await some responses.

Thanks,