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HELP! Re-geared to 4.56 and hear a horrible grinding noise from rear end

F

fangskate

NAXJA Forum User
Location
Colorado Springs, CO
Hey guys,

I recently had a shop re-gear my front (Dana 30) and Rear (Chrysler 8.25) axles on my 2000 xj. The 8.25 was a swapped axle and did not come stock.

I went from 3.55 gear to 4.56. I have gone maybe 30 miles on her since the work was done and ever since it was done I hear a terrible grinding noise. It started off as only making a noise when I would barely get on the gas or get off the gas but now it remains longer after getting off the gas as well as staying on it. It has gotten louder and more violent.

I took it back to the shop yesterday and they told me they are literally stumped and have double checked/triple checked all of the settings on the rear end / ring and pinion.

The center of the pumpkin gets very hot after only a couple mile drive and both the driver side and passenger side stay cool compared.

Any help would be greatly appreciated on helping me figure out WHAT THE HELL went wrong here.

Is there anything special about re-gearing a chrysler 8.25 that they may somehow may not know??

And just to clarify, it is 100% coming from the rear end and it is not coming from the transmission or transfer case.

Thank you in advance!
 
Mine growled for a year after the same change. Noise there is pretty much a given, it is evidently unavoidable in the 8.25. Even stock factory gears have a 50% chance of noise.
But, it still means you need to check every thing that could be a problem, including the TC output bearings and runout.
 
831_xj said:
He did take it back.. but who knows. Did the change the shaft bearings in the 8.25?
Click to expand...

Yea , I bought and supplied them with a master bearing install kit so everything is brand new. The master install kit and the ring/pinion were both Motive Gear brand new parts.

Thank you guys for your suggestions and thoughts. I'm just at a loss and the shop is kinda hinting that if they have to take the axle apart again they are going to charge me for it.
 
fangskate said:
Yea , I bought and supplied them with a master bearing install kit so everything is brand new. The master install kit and the ring/pinion were both Motive Gear brand new parts.



Thank you guys for your suggestions and thoughts. I'm just at a loss and the shop is kinda hinting that if they have to take the axle apart again they are going to charge me for it.
Click to expand...


They shouldn't charge you if they messed up
 
Pull the rear drive shaft off and drive in 4WH (front wheel drive in this case) see if it makes any noise just rolling along with no load on it.
 
That much heat in the center of the pumpkin would make me think there is a problem with the pinion bearing. Perhaps they didn't get the new race set in properly? Also, did they use a solid spacer in place of the crush sleeve, or get a factory (Chrysler, not Motive) crush sleeve? If not, get that changed out now, so that in 2000 miles, the axle doesn't grenade.

David Bricker / SYR
 
What exactly did they check and miss?

There isn't a heck of a lot to an axle really. The reason it isn't a DIY for many people is the investment in tools and patience & time to set it up right which may mean repeatedly changing shims until the preloads are in spec and the pattern looks good.

As David said pinion bearings installed correctly? Deep low pitch noises are often carrier bearings. If the adjusters weren't tightened correctly your carrier bearings may be junk. The R&P set generally howl or whine rather than grind.
 
UPDATE

So I took her to another shop yesterday and the owner helped me out allot buy fully investigating the cause of the noise. He checked their work and said that they had done a good job on the gears; the backlash and the preload on the pinion bearing may be a bit extreme but overall was great work. He checked for things like bad wheel bearings and eventually narrowed it down to it being a SYE issue. He believes that the difference between the two axle pumpkins could have been just enough change in the driveshaft angle to create the issue and requires an SYE.

What I think is a bit strange about that is the first shop immediately thought that was the issue when I brought it in but then said its coming from the rear end. But regardless I will have to agree with the second guy because it definitely sounds more external than internal and closer to the front than being all the way in the back.

So hopefully when I swap in my SYE All will be good again. Thank you all for the thoughts and suggestions ; very much appreciated
 
I'm not sure how the SYE is going to cause the excessive heat in the center of the axle you describe. Did you swap a 8 1/4 axle in for a Dana 35? Swapping in a different 8 1/4 should not have any difference in pinion angle.

David Bricker / SYR
 
Yes , it was a Dana 35 to a Chrysler 8.25 Swap....I'll be honest, it does not sound like an SYE problem but I am so green when it comes to this stuff I really don't know what I am looking for.....Feels like allot of vibration and some grinding noise when I press the gas and let off the gas (usually at higher speeds beginning at 30MPH) Now the grinding / vibrating lasts longer when I let off the gas than it did before.

I am at a loss.......Sounds like it is coming from the middle or even the front of the vehicle... The front drive shaft is currently removed and the noise still occurs.

Still willing to hear any thoughts or advice anyone would have other than whats been discussed.
 
Jimthej said:
Mine growled for a year after the same change. Noise there is pretty much a given, it is evidently unavoidable in the 8.25. Even stock factory gears have a 50% chance of noise.
But, it still means you need to check every thing that could be a problem, including the TC output bearings and runout.
Click to expand...

Had to throw in my .02 on this one. Complete BS.

I've had 4 different 8.25s regeared over the past 15 years (in different XJs) and have never had gear noise AT ALL. Not under load, not coasting. 3 were to 4.56 and 1 to 4.10. Used Motive or Yukon gears and master install kits with either Timken or Koyo bearings. It takes a person who knows how to setup a 8.25 and is detail oriented.

If you don't figure it out, we have a f'n awesome Naxja gear dude up in NoCo.
 
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