Real time help please 4spd transfer case

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Jan 25, 2006
Will a mismatched idler gear and output gear make a noise do a while?

I’m getting a noise and feeling every rotation on a new rebuild.
Preload was good with new bearings.
It is pretty pronounced on coasting.
Almost sounds like a gear is hitting the case.
Also idler gear thrust was all in spec.
My opinion? Yes, mismatch is likely to be noisy if the difference in wear was significant. Blow apart any time soon? Probably not.

Being louder when coasting or not under load would be expected.

Have you rechecked the thrust bearing clearance since this issue began? What you are describing sounds exactly like the idler slapping back and forth from too much clearance. Ask me how I know.
I took it all apart. And there was metal on the plug. I drained everything the fluid didn’t look bad. Took the top cover off, and everything looks great.
Smooth as butter. The rest clearance is still fine. All the gears lined up. There is still preload. I did find A few nicks on the input gear. I have a new one of those That I will replace.

This is all after I blew up the old one in spectacular fashion. I am going to look at the rear end and the driveshaft next. The driveshaft seemed fine when I had it out, I greased the u joints. Everything seem tight.

The sound is weird almost like a gear hitting the case every rotation. I can feel it through the transmission.
Rear end looks fine.
Input gear wear/chip


An odd sound wile coasting can also be a bad pinion bearing in the rear diff.
Maybe drop the rear drive shaft, jack up a rear tire and spin the pinion shaft by hand and see if you feel anything. My bearing was damaged from water, drove in too deep water without having raised axle breather.
That feel good took the cover off and spun it
You’ve reused a gear from the old case “that blew up in spectacular fashion.“ One or more of the teeth is actually damaged, just not hi-vis.

I made this mistake on a customer’s tcase...about 27 years ago. Luckily I discovered it before I reinstalled the unit.
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I think that was it. I rebuilt it today with a new idler gear and a new to me input gear. Drove it around the block and sounded good. Fingers crossed.
This was a long day!!!!!

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