What normally causes the spider gears to need replacing?

[Signe]

I bought my '03 KJ about 10 months ago (with about 48k miles) and immediately had the transmission, transfer case, and the front and rear differentials serviced.

The mechanic called me over and showed me some metal shavings from the rear differential that he said came from the spider gears. Since this was covered under warranty, I told him to go ahead and replace them (which he did.)

What normally causes spider gears to need replacing? The mechanic told me the front differential was fine and so was the transfer case and transmission.

Thanks.

P.S. I'm not experiencing problems of any sort. I've been meaning to ask this question simply out of curiosity. Another thing the mechanic told me is it's not a good idea to be in full-time 4WD (even though the owner's manual says it's okay.) He said to keep it in 2WD and only use 4WD if I have to (i.e. snowy conditions, off-road use, etc.)

 

[JeepJeepster]

You can use full time anytime you want to, there is nothing wrong with it. It will put more wear and tear on the front drivetrain since it will be putting torque on it where normally its just spinning. I wouldnt drive around on a sunny day in full time if its not needed but you can if you really want to.

How much metal was in the diff? Its normal for the magnet to be covered in very fine metal shavings. What did the spider gears look like?

 

[Signe]

IIRC, they were larger than fine, metal shavings. However, they certainly weren't "chunks" by any means.

I didn't notice anything wrong with the way my KJ was driving. I had the drivetrain serviced simply because the dealership gave me a 90 day warranty and I figured if any repairs were needed, that would have been the time to get them done.

My KJ was 100% loaded from the factory: leather heated seats, Selec-Trac, sunroof, automatic ****** w/ overdrive, infinity speakers, premium wheel package, towing package, etc. My hunch is all these options aren't the sign of someone who bought the Jeep to go 4-wheeling. Consequently, 4-wheeling was probably not the reason the spider gears needed to be replaced.

 

[JeepJeepster]

Normal offroading wont hurt the spider gears. If you get water in the diff the bearings would probably go out before the spider gears would.

I cant think what would cause the spider gears to go bad and nothing else other than bad spider gears from the factory.

Putting bigger tires on and beating the snot out of it could wear them out but it doesnt sound like thats been done to that Jeep.

 

[J-Thompson]

improper set up can cause the spiders to go out
question for you
the mechanic who did the work was he a dealer mechanic or was it
"bob's mechanic shop"
if it was bob's then you should have had a locker or LSD installed
if you want to keep factory on road manners then a Detroit TT would be the way to go
I know this is a little late but still maybe good info for some one else