I have a 98 Cherokee starting at 55 mph I get a humming noise that sometimes oscillates. It doesnt do it with the front drive shaft removed, or with the rear drive shaft removed pulling only off the front axle. It does however do it with it in 4wd at 55 mph +. It has a 2" econo lift (spacers and blocks) and didnt do it untill after the lift was installed. It has a RE economy SYE, rear driveshaft has double cardan and has been balanced and lengthened. Front driveshaft completely rebuilt and checked for length and re-balanced twice, new front wheel bearings, new front axle u-joints. I shimmed the lower control arms 5/16" to move pinion angle close to stock(whatever that is) then alligned it. All specs are perfect including caster. Transfer case front output feels good, front diff feels good. Removed front diff cover and couldnt see any problems. Leaning towards front diff spider gears though. Remember it doesnt do it in 4wd with rear shaft removed, or 2wd with front shaft removed.
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Humming noise
- Thread starter Wrectec
- Start date
- Location
- Westminster, SoCal
Wrectec said:
How did you setup the rear pinion? Did you point it towards the transfer case? (or rather 1 ~2 degree below the rear tcase output?)
actually I just reread your post and got confused: it seems that there is no noise if you drive with either one of the driveshafts: either only front or only rear, is that correct?
- Location
- Westminster, SoCal
Hmmm I might be reaching here, but it kind of sounds like it's in 4wd maybe? Check the tcase linkage and make sure that it fully disengages the 4wd when you put it into 2wd.Wrectec said:
I just checked the linkage, popped the rod off and it was in 2wd, worked the rod between 2 and 4wd it all seems ok externally, I guess the next thing I'll do when I get back to work is get all four wheels off the ground and run it in 2wd and make sure the front shaft is'nt trying to engage. Thanks for the help.
Got all four wheels off the ground took it up to 55 mph and front drive shaft is not moving so transfer case ok. Vehicle is humming a fine tune so I sniff around a little while my buddy keeps it between 55 and 60. My rear diff is just screaming, shut er down. Removed the fill plug (8.25) and fluid is foam, and foam doesnt lube. Removed diff. cover foam foam foam. what the! Vent tube is fine, no metal at all any where, cleaned everything out and used a different brand of lube than I usually do. Test drove and humming is gone for about 3 miles then slowly and slighty returns to about 30% of what is was before, so tomorrow I'll see if I have foam again, but it looks like pinion and carrier bearing time. Don't understand why the front driveshaft removal made a difference though? Thanks for the help.
- Location
- Westminster, SoCal
Wrectec said:
Yeah, swapping out the bearings does seem like a good idea at this point.
I rebuilt the rear end. The outer pinion bearing had some bad wear, and the
right rear axle bearing had spun. I replaced all bearings and races in the rear end, staked the rear axle bearings and installed a new crush sleave. (Tech notes: used an old CJ front bumper to hold pinion yoke, cut a hole in the center of one end of the bumper big enough for my pinion nut socket to fit, then drilled four holes to bolt the bumper to the yoke with u-joint bolts, then tourque away untill I got 30" lbs. of drag with tourque wrench [tedious]. Then took a long piece of pipe and welded a nut to the end to go through axle tubes and adjust gear lash and carrier bearing pre load.).....Test drove and vibration still there. Gear lube still foaming. Got vehicle back on lift and noticed at slower speeds the driveshaft is out of round, at 60 mph when I have vibration the drive shaft is straight but the rear axle is taking the vibes and causing the lube to foam. Took driveshaft and RE economy SYE back to Driveline shop, they found the SYE flange bolt holes to be off center, they rebalanced as an assembly and wa la vibration is gone. Talk about live and learn.
right rear axle bearing had spun. I replaced all bearings and races in the rear end, staked the rear axle bearings and installed a new crush sleave. (Tech notes: used an old CJ front bumper to hold pinion yoke, cut a hole in the center of one end of the bumper big enough for my pinion nut socket to fit, then drilled four holes to bolt the bumper to the yoke with u-joint bolts, then tourque away untill I got 30" lbs. of drag with tourque wrench [tedious]. Then took a long piece of pipe and welded a nut to the end to go through axle tubes and adjust gear lash and carrier bearing pre load.).....Test drove and vibration still there. Gear lube still foaming. Got vehicle back on lift and noticed at slower speeds the driveshaft is out of round, at 60 mph when I have vibration the drive shaft is straight but the rear axle is taking the vibes and causing the lube to foam. Took driveshaft and RE economy SYE back to Driveline shop, they found the SYE flange bolt holes to be off center, they rebalanced as an assembly and wa la vibration is gone. Talk about live and learn.
jrsxj98
DILIGAF
- Location
- Crawlorado
You took the flange and the driveshaft in together correct? I have the same sound but I have learned to ignore it.
Correct. They said the bolt holes were not centered to the center where it slides on the out put shaft, like off to one side. They checked the drive shaft and it ran true then the SYE and it ran true but when bolted together it was off, they just rebalanced it as an assembly and I had it going 80mph with no humming noise. I dont know how bad yours is but if it's foaming the diff fluid it will damage your bearings like mine did. Air does not lubricate.