Squint

OK, so I heard the dreaded rumble from the rear end last week . It comes and goes, sometimes louder than other times, but most often it is audible when driving very slowly, as in backing out of the driveway, parking lot, etc. So I crawl underneath for a look, and I see that the right side axle tube is separating from the diff housing...it has a shiny, polished bare metal ring around the axle tube where it is flexing around and rubbing the diff housing. My assumption is that this is not repairable, so I will need to replace the rear axle. It is a 1999, has a 4.0 6 cyl 2wd automatic trans, Chrysler 8.25 axle, and best I can tell, it has 3.73 ratio(slightly less than 4 turns of the driveshaft for each rotation of the rear wheel). Two questions: is this repairable maybe by tack-welding the tube to the housing (please oh please)? Or do I need to replace the rear axle unit? And question two: what would be the positive/negative affects of changing to the 3.55 ratio? Better gas mileage? poorer acceleration? (don't care about drag racing anyone). Not interested in going to a 4.10 ratio.

Reason I'mma asking is bc the local jy has a C 8.25 with the 3.55 ratio for a good price ( $300), but haven't found one with the 3.73 ratio. Might be one @ u-pull-it for cheaper but longer drive to get it.

Thanks!!

Squint

mitchlikesbikes

why not get the other one and swap your gears into it?

Jamie57

Are you really sure it's coming out? I ask because I've seen a shiny spot on at least 4 XJ 8.25 rears lately and it's all from the cable tie that holds the e brake cable. I just sandblasted one and the tube IS welded to the carrier housing.

Squint

Hmmm, didn't think of that one. I'll crawl under there again to see if I'm overlooking that possibility. I'll also try to post a pic either way.

Thanks!

PS I guess if the shiny spot is a rub from a cable tie, that means its a whole rear axle swap needed.....

tonytwotimes

If you do need to swap the axle the difference in gearing is going to be pretty negligible in my opinion, especially because it's a 2wd. It wouldn't be worth it to me to swap the gears for such a close gear ratio especially since if you have not done it before you have a good chance of just swapping a grenade into the rear end. u pull it is like $150 for a loaded axle tube out here vs. cost of another axle, cost of a kit for the swap (might as well do it right) and the possible cost of another axle after that one takes a big ****.

zjguy

why would this be means for a rear axle swap if its a cable tie rubbing all its doing is polishing the tube and the sounds your hearing leads me to believe you have bad carrier/pinion bearings or a bad wheel bearing/s

cruiser54

I'm betting it's a 3.55 rear end in the first place. Gotta find out what teh real problem is anyway.

Squint

Well somebody musta put the "stupefy" spell on me because Jamie57 is exactly right, its a zip tie rubbing the shiny spot onto the axle tube. Please don't revoke my forum membership.

I checked the u-joints and they are tight, so I'm thinkin' it's a bearing somewhere?

cruiser54

LOL. Gotta love it!!

Squint

Hey Cruiser, any guidance on how to trouble-shoot rear end noises? I've watched a bunch of rear axle bearing replacement videos, I can handle that repair, but how do I know it's the axle bearings making the noise?

cruiser54

Jack up the rear and start turning things and listening. USE JACKSTANDS.

How does the noise change while driving? On the gas. Off the gas. Going around right turns, left turns?