Differential question - Pinion Bearings Replace or Not??

[Shankster]

I’m hoping to get some input from some of you who have experience troubleshooting / servicing / repairing differentials. My plan in the next few weeks is to replace the stock open carrier in my rear differential with a helical gear (Torsen style) LSD in my 02 Liberty 3.7L 4x4 with the 8.25” Chrysler rear end.

In RWD my stock diff whines loudly under load / acceleration. It starts at around 15 or 20 mph and gets louder as speeds increase and the frequency increases with wheel speed. If I’m in full time 4WD the noise is much less or maybe even completely gone (since the front diff is taking on half the load I assume). There is little or no noise when coasting. I figured it was the pinion bearings making the noise but since I opened it up to inspect the gears and change the gear lube I’m not so sure now.

Both the ring and pinion gear looked good – I didn’t see any strange wear or chipped teeth. I did put my dial indicator on the ring gear and was out of spec – I got between 12 and 15 thousandths backlash on the 4 or 5 teeth I checked. I didn’t attempt to adjust that. I imagine that is contributing to the noise.

Another thing that jumped out at me was the large amount of play in the center pin – it does not fit snug in the carrier housing and has significant play. I bet I was able to move a wheel 10 degrees in either direction before it would re-engage the spider gears and I could see the pin shifting from one side of the bore to the other. I’ve been watching a bunch of Youtube videos of guys servicing these and I didn’t see any play in the center pins on any of them – they were all super snug as I’m sure they’re supposed to be. So I will obviously address that when I install the new LSD but what I want to know is if that could be causing the noise from the diff? I’ll definitely change out the pinion bearings and races if I have to but based on the amount of work that takes, I’d like to avoid doing so if it seems the pinion bearing is good as I’m betting the pinion bearing replacement would be 75% of the work. My thought is that when I get the carrier out and disconnect the driveshaft, I play with the pinion shaft and get a feel for whether the bearing is good or not – if it feels crunchy at all I replace it, if it has any discernable side to side movement I replace it – otherwise I leave it alone, reinstall the ring gear and tone ring on the new LSD carrier and install new carrier bearings and races, adjust for backlash and hope the whine is gone.

Does this make any sense or should I just go to the (significant) additional effort of replacing the pinion races and bearings even if they seem good?

Some other background – I know virtually nothing of the history on this vehicle. I bought it with a blown engine. It was pampered cosmetically but not sure how well it was maintained. Based on the impression I got from the lady I bought it from it was likely never off road and probably never towed anything. When I removed the speed sensor (troubleshooting a speedo issue) from the top of the housing there was a fairly large piece of tooth stuck to it – not sure where that had come from – could have been ring, pinion, spider or tone ring tooth and I foolishly flicked it on the ground never to be found again. When I had the thing opened up I checked all the teeth on everything carefully and didn’t find any chips or missing teeth. I suspect there had been a catastrophic diff failure at some point and someone had replaced the internals but missed that piece of tooth magnetically stuck to the speed sensor when they were mucking out the debris. Maybe they put the wrong center pin back in or failed to replace a damaged center pin?? Just guessing here.

So again, my question is – should I replace the pinion bearings and races, even if they seem good?

 

[tommudd]

Do it right from the get go and replace all bearings, seals etc
Then you are sure , plus if it is stock being that old it deserves it
If you are putting a locker in, then there will be more power to the whole diff so like I said above do it right and be done

 

[JeepJeepster]

That crush sleeve was a BEAR to crush on mine. I had to wedge a breaker bar against the frame then use my floor jack on another breaker bar to crush it. Im thinking some of it was due to the outer pinion bearing being super tight on the pinion gear. You can buy a timken rebuild kit at rockauto, timken is what my 04 8.25 had in it from the factory.

https://www.rockauto.com/en/catalog...4760,drivetrain,differential+rebuild+kit,2224

 

[Shankster]

Do it right from the get go and replace all bearings, seals etc
Then you are sure , plus if it is stock being that old it deserves it
If you are putting a locker in, then there will be more power to the whole diff so like I said above do it right and be done

I know, I know, I should do it right. Like I said though, I suspect it's been redone at some point in the past, maybe recently and if I do everything but the pinion bearings it seems pretty straightforward - adding the pinion bearings makes it a bear of a job by the looks of it which will definitely challenge my capabilities and tools.

 

[Shankster]

That crush sleeve was a BEAR to crush on mine. I had to wedge a breaker bar against the frame then use my floor jack on another breaker bar to crush it. Im thinking some of it was due to the outer pinion bearing being super tight on the pinion gear. You can buy a timken rebuild kit at rockauto, timken is what my 04 8.25 had in it from the factory.

https://www.rockauto.com/en/catalog...4760,drivetrain,differential+rebuild+kit,2224

That's one of the parts that scares me - 250 ft-lbs I've heard (sounds like yours was even more!), and me crawling around under the thing as it sits on jack stands. Then if you overdo it on the torque you need to pull it apart again and order a new crush sleeve. I just see a potential for me screwing the thing up so wonder if my odds for success could be better if I just leave the whole pinion setup alone (assuming it all seems good).

Thanks for the link (Rock Auto won't deliver to my town any more - something about the local sales tax?). I got turned off of Timken when a couple of their wheel bearings failed on my (raced and very abused) Subaru after about a year - could have been mechanic (me) error though so I should give them another chance. I think the other brand I see out there is Koyo? Do you hear anything good about them?

 

[tommudd]

I know, I know, I should do it right. Like I said though, I suspect it's been redone at some point in the past, maybe recently and if I do everything but the pinion bearings it seems pretty straightforward - adding the pinion bearings makes it a bear of a job by the looks of it which will definitely challenge my capabilities and tools.

Go ahead and chance it, only cost you a few hundred to do it right later on
No use doing half a job
If it could of been rebuilt at some point that maybe good, but did they do it right?
In your initial post you stated you had some noise etc , right ?
So while it maybe somewhat of a bigger job than you are used to doing, may get someone else to " help " you to do it right

 

[tommudd]

That's one of the parts that scares me - 250 ft-lbs I've heard (sounds like yours was even more!), and me crawling around under the thing as it sits on jack stands. Then if you overdo it on the torque you need to pull it apart again and order a new crush sleeve. I just see a potential for me screwing the thing up so wonder if my odds for success could be better if I just leave the whole pinion setup alone (assuming it all seems good).

Thanks for the link (Rock Auto won't deliver to my town any more - something about the local sales tax?). I got turned off of Timken when a couple of their wheel bearings failed on my (raced and very abused) Subaru after about a year - could have been mechanic (me) error though so I should give them another chance. I think the other brand I see out there is Koyo? Do you hear anything good about them?

Stick with Timken , raced and very abused and they failed , well ........whose fault was that?
Koyo LOL

 

[Shankster]

Go ahead and chance it, only cost you a few hundred to do it right later on
No use doing half a job
If it could of been rebuilt at some point that maybe good, but did they do it right?
In your initial post you stated you had some noise etc , right ?
So while it maybe somewhat of a bigger job than you are used to doing, may get someone else to " help " you to do it right

Well I'll have the entire parts kit before I dive into the project so I guess I'll see how motivated I feel - I'm almost hoping the pinion bearings feel crunchy or loose and then I'll be forced to do the right thing with no chance for regret. I have a buddy with every tool under the sun and a new lift I might even ask if I can use. Trouble is, things take at least 2x longer with him as he has a tendency to BS more than work

I guess I'm still hoping someone will comment on whether the excessive play in the center pin could create the whine I described. The spider gears can't be engaging at quite the angle they're supposed to because of that loose pin. (and note that the threaded lock pin that goes through and retains the center pin seemed tight, it's the center pin itself that's loose in the carrier body)

 

[tommudd]

Of course the center pin, if that loose will cause some issues
Have you ever done a complete differential rebuild ?
and please don't say you watched a You Tube video

 

[JeepJeepster]

Koyo is whats in my rear diff now as thats what came with my install kit. I didnt know what the rear diff had in it till I took it all out. Shouldve waited to see what was in there then bought the parts....

If you take your time you wont have any issues with passing up the torque. Only people that use a big impact to tighten the pinion do that...

 

[Shankster]

Of course the center pin, if that loose will cause some issues
Have you ever done a complete differential rebuild ?
and please don't say you watched a You Tube video

I know the center pin ain't right (and could be a catastrophe waiting to happen) - just want to know if that might cause the whine. I've never done any kind of diff work other than change the lube. There's a first time for everything though I suppose.

 

[tommudd]

I know the center pin ain't right (and could be a catastrophe waiting to happen) - just want to know if that might cause the whine. I've never done any kind of diff work other than change the lube. There's a first time for everything though I suppose.

Yes it could possibly
And yes there is a first time for everything, in most cases
But rebuilding and setting up a differential, if not done right, could be a costly learning experience
It's not horse shoes or hand grenades' , just get it close is not an option

 

[Shankster]

Koyo is whats in my rear diff now as thats what came with my install kit. I didnt know what the rear diff had in it till I took it all out. Shouldve waited to see what was in there then bought the parts....

If you take your time you wont have any issues with passing up the torque. Only people that use a big impact to tighten the pinion do that...

OK, thanks. I have a buddy with a little (1/4") beam style torque wrench (for tightening carbon bicycle parts) so hopefully I can monitor the resistance on the bearings as I ramp up the torque.

So are you also saying stay away from Koyo? - I was just googling Koyo vs Timken and it seemed roughly a tie on who liked which brand better. I got the impression Koyo are generally made in Japan and quality is consistent but Timken can be either US or China so quality is less predictable. Someone also said that Koyo had purchased Timken. As always, a bunch of people seemed to be throwing out opinions without actually having any experience so not sure what to believe,

 

[Shankster]

Yes it could possibly
And yes there is a first time for everything, in most cases
But rebuilding and setting up a differential, if not done right, could be a costly learning experience
It's not horse shoes or hand grenades' , just get it close is not an option

I hear ya. I could certainly fail but I'm determined to do it myself. I'm a reasonably capable shade-tree mechanic (mostly at the other end of the vehicle though) and also a Professional Engineer so will take my time and do my research and hopefully end up OK.

 

[tommudd]

1/4 inch torque wrench is not going to cut it , need a REAL one
Need a 1/2 drive at least

 

[Shankster]

1/4 inch torque wrench is not going to cut it , need a REAL one
Need a 1/2 drive at least

The 1/4" would be to measure the resistance on the pinion bearings - there is a spec for that - I forget but it's like 10 inch pounds. You crank down on the pinion nut a little at a time and measure the rotational torque required to turn the pinion shaft as you go.

Don't think my 1/2" torque wrench will be much use for installing the pinion nut anyway - it goes to 150 ft-lbs and it sounds like the torque required is more like 250 ft-lbs so as JeepJeepster was saying, it'll take some force - in my case a long breaker bar with 3 feet of 2" pipe cheating some more.

 

[tommudd]

The 1/4" would be to measure the resistance on the pinion bearings - there is a spec for that - I forget but it's like 10 inch pounds. You crank down on the pinion nut a little at a time and measure the rotational torque required to turn the pinion shaft as you go.

Don't think my 1/2" torque wrench will be much use for installing the pinion nut anyway - it goes to 150 ft-lbs and it sounds like the torque required is more like 250 ft-lbs so as JeepJeepster was saying, it'll take some force - in my case a long breaker bar with 3 feet of 2" pipe cheating some more.

LOL ok
I've only been working on/ building vehicles / mostly 4x4s for close to 50 years
Carry on, I'm done

 

[JeepJeepster]

I used a 1/4" beam style torque wrench on my pinion, worked perfect. You must use a beam style or dial torque wrench for this, no other way to do it.

Also bought a new 1/2" torque wrench that went up to 250lb/ft but that was a waste of time. Maxed it out at 250 and still had play in the pinion.

Follow the FSM to a T when adjusting the side adjusters. They put stuff in different places for the diff, so you have to read the entire section on the rear diff to get all of it.

 

[tommudd]

Guess I was taught and have only use good torque wrenches and do not mess with 1/4 toys
Never knew anyone to use 1/4 on anything but RC cars
One of my Snap On's goes way beyond a measly 250

 

[JeepJeepster]

Im sort've confused what you mean by that Tom, you've got to use a small (typically 1/4") beam style or dial style torque wrench to check the rotating torque of the pinion. Spec is only 10-30 in-lbs for new bearings.

Just checked the FSM. The minimum pinion nut torque is 210 ft lb, thats why I bought a new torque wrench. I torqued it to 210 and that did nothing, so I maxed it out at 250. Once that did nothing I moved on to the floor jack and breaker bars. The pinion flange holder I bought from bleepin Jeep worked great.