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Low to High Pinion

B

Box kicker

NAXJA Forum User
Location
Cherry Point, North Carolina
I recently switched my front axle from a low pinion Dana 30 with 3:55 Gears which came stock on my '00 XJ Sport to a High Pinion Dana 30 3:55 Gear off of a '97 XJ Country. I am now getting bad vibrations and a burning smell when I go over 45 mph. The differential has fluids. It needs an alignment. what could this be?
 
How did you do the brakes? Which rotors pads and unit bearings did you use?
 
I haven't tried removing the drive shaft actually. I got the alignment, I bled the brakes normally and I don't get that burning smell anymore. I balanced the tires as well. I suppose I can drop the front drive shaft and if it stops, then it's U-joints? it doesn't matter if I'm using a rear low pinion axle off of a 2000 XJ Sport and a front high pinion axle off of a 1997 XJ Country?
 
What did you use for rotors?

Unit bearings are the wheel bearings - they've got the axleshaft going through them, a giant 36mm nut on the outside, and three 13mm 12-point bolts holding them in from the back of the steering knuckle.

If you used the rotors from your old jeep (or to match your jeep's manufacture year) you HAVE to use the wheel bearings/unit bearings off your old axle, too. If you use the rotors from the jeep that the axle came from (or to match its manufacture year) you have to use the wheel bearings/unit bearings that came with it, as well. The reason is that halfway through 1999, they changed the type of brake rotor and unit bearing used and they've got some different dimensions, so if you mix 1999.0 and earlier brake rotors with 1999.5 and later unit bearings or vice-versa, if you can even get the caliper onto the jeep there's a strong likelihood of it binding or the brakes dragging.
 
The brakes right now work like they did before I swapped the axle. Are these bearings applicable to all XJ's of those years? I've been reading of a lot of changes that aren't incorporated on all jeeps that are said to have come out on that year. The rotors as far as I can tell are just casted differently, the brake calipers, steering knuckles and pads are applicable to both axles though; at least by part numbers
 
Yeah, the calipers, steering knuckles, and pads are fine, no worries there. It's the rotors and unit bearings you have to be careful with.

Here's a good writeup on identifying what rotors and unit bearings are in use on your jeep: http://www.naxja.org/forum/showthread.php?t=1058413

Note the height of the pilot ring surrounding the axle nut on the unit bearing. That's probably the fastest way to identify one vs the other - the one with the taller pilot ring is intended to only be used with the rotors with the rounded "hat" corners. Using them in another combination can result in things not lining up the way they're supposed to.
 
the only thing I have changed on the new axle is I took the rotors from my 00 axle (because they were not junk) and replaced the rotors on the 97 (the ones that came with it were far more rusted) other than that it's a 97 high pinion axle. How would that 1/8 of an inch cause binding? from what I'm interpreting of the differences between rotors, it's just the way they were cast and the thickness of the rotors.
 
It's not just the rotor dimensions that cause it, it's the unit bearing dimensions combined with that. If you use the wrong two together it either moves the rotor 1/4" one way or the other from what I'm reading here (since the unit bearing dimensions are changed to account for the rotor dimension change) which can put the rotor too close to the caliper bracketry and/or too far to one side or the other for the slides to accomodate things easily.

Basically, it's not a good idea. And the symptoms you list are exactly what you can end up with if you use the wrong rotor/unit bearing combination, which it sounds like you have. I feel like I'm pulling teeth here trying to get relevant info and explain this...
 
Should be the same length, I see a part number 5300 5542 front driveshaft for all 97-99 and 00/01 4.0/AW4/4x4 vehicles, LP30 or HP30. Dana/Spicer driveshaft catalog J321-CV says it's 30.66" long, not sure if that's extended, collapsed, or ride height.
 
kastein said:
Should be the same length, I see a part number 5300 5542 front driveshaft for all 97-99 and 00/01 4.0/AW4/4x4 vehicles, LP30 or HP30. Dana/Spicer driveshaft catalog J321-CV says it's 30.66" long, not sure if that's extended, collapsed, or ride height.
Click to expand...

you are completely right, whoops my bad.
 
No worries, wish I even knew how many times I'd gotten something completely wrong on here :dunce:

If I had to guess you were thinking of the AX15 vs AW4 shaft differences, AW4 front driveshafts are 1.41" longer.
 
I was mostly talking about the burning smell - that's generally what causes it. Check to see if it bound/dragged for a while and roached one of the pads completely, the smell would go away when the pad wears down.

Vibes, I don't know.
 
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