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Measuring rear diff. pinion rotating torque
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Author:  BoarX [ Sun Nov 18, 2018 11:50 pm ]
Post subject:  Measuring rear diff. pinion rotating torque
Hi all,

I need to replace leaking rear diff. pinion seal on my 2006 Liberty CRD Limited. With the driveshaft removed and the pinion nut still on I am trying to measure the pinion rotating toque with inch/pound wrench, but cannot even get a reading. It is surely less than 25inch/pound. What is the typical value? I suspect I need more sensitive torque wrench - any recommendations?

(my rear calipers and rotors are off, no oil in diff. case, had to replace axle seal)

Thanks in advance,
Alex
Author:  WWDiesel [ Mon Nov 19, 2018 1:15 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
That value is for new bearings with NO carrier installed. As the bearings wear in and get set, the preload will decrease.
Used pinion bearings give less resistance to rotation as they are already worn in and set. This is normal.
Torque the pinion nut down until slight resistance (preload) is felt when turning it by hand.
The crush sleeve is designed to hold the pinion bearings in a preloaded state once you set the preload correctly.
A used crush sleeve has already been crushed when originally installed so care must be taken not to over crush it on used installations.

Over torquing the pinion nut will increase preload on the bearings and to much preload can cause them to overheat and fail.
(pinion shaft will have high resistance to rotation by hand)

Too little preload on pinion bearings can cause lots of noise and early failure of the bearings and possibly the pinion and ring gear.
(pinion shaft will have no resistance to rotation by hand)

Hope this helps?
:SOMBRERO:
Author:  u2slow [ Mon Nov 19, 2018 6:25 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
Save yourself a bunch of guesswork and get a crush sleeve eliminator. That way you can trial and error the setup as many times as you want, without the seal in place. I used Ratech 4114 spacer... got it from summitracing.

The tool for the job is a dial-type inch# torque wrench... usually about $200. You can't use a click type because the torque from static to rolling is higher than simply rolling torque. You want the rolling torque value.
Author:  Mountainman [ Mon Nov 19, 2018 10:18 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
I use a cheap bar style inch pound torque wrench (about $20) I had to make an adapter to get from 1/4" to the 3/4" socket. Measure while you rotate it around in a smooth/ consistent manner.
Author:  BoarX [ Tue Nov 20, 2018 9:31 am ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
Thanks so much guys! This is my first foray into the land of axles, read your responses, spent couple of days watching clips on Y and finally starting to get it. For the moment my plan is to replace the pinion seal and re-tighten the pinion nut back to exact same state as before. Playing with crush sleeve or its eliminator requires pulling the front pinion bearing as a minimum and most likely the carrier with subsequent readjustment of the carrier bearings preload and the backlash - am I correct? Frankly, I am not yet ready to plunge that deep.

Quote:
The tool for the job is a dial-type inch# torque wrench... usually about $200. You can't use a click type because the torque from static to rolling is higher than simply rolling torque. You want the rolling torque value.


Thanks, I realized that early on sensing how easy was it to rotate the pinion. We used to have boxy dial-type tool at work, but it has mysteriously disappeared, I now can guess where ;)

Quote:
I use a cheap bar style inch pound torque wrench (about $20) I had to make an adapter to get from 1/4" to the 3/4" socket. Measure while you rotate it around in a smooth/ consistent manner.


Figured that one too, got that same type of wrench and 1/2" to 3/4" socket adapter from Menard's. Problem is, the tool I got could hardly measure anything below 20 inch/pounds, need to either find more sensitive one or use the breaker bar of known length and a fish scale :)

Cheers,
Alex
Author:  Mountainman [ Tue Nov 20, 2018 5:30 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
Cool, I would use a new nut and lots of red locktite. Please let us know how it holds up.
Oh, so you plan to tighten it down to where you can first feel some slight drag? If you have a 4' breaker bar or longer with 3/4" drive, you should have no trouble slowly getting to the point of some drag. Tighten the nut with the smallest possible increments with checking each time for drag. If you over-shoot you probably need yet another new nut.
Author:  BoarX [ Wed Nov 21, 2018 1:11 am ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
Guys, you will laugh! Got myself an $5 fish scale from Walmart, no breaker bar necessary, just put the scale hook into one of the pinion flange holes and measured the rotation resistance force at more or less constant speed. Guess how much was it? Measly 1.5 pounds! Given that the flange holes are on almost exactly 2" radius, this gives the torque of 3 inch/pounds (pound*inch to be precise). There is still no perceivable axial play of the pinion shaft. Could such a low torque value be the result of silly me filing the diff. with synthetic 75W-140? Needed to urgently tow 5,000lb (realistically more like 6,000+lb) boat and couldn't find non-syn 75W-140 nearby. The diff is currently drained, but oil is still everywhere. For one thing, that synthetic oil must have exacerbated the leaks through the seals.

Oh well, live and learn!
Cheers,
Alex
Author:  WWDiesel [ Wed Nov 21, 2018 12:27 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
Oil type should have negligible if any effect on bearing preload which equates to resistance of pinion rotation which you are measuring.
Author:  BoarX [ Thu Nov 29, 2018 9:43 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
Alright, finished, fingers crossed. Before removing the pinion nut I used a caliper to measure the protrusion of the pinion shaft in respect to the nut. Depending on the point of measurement the number varied from 4.1 to 4.6mm. Got a new nut, measured its thickness and calculated the pinion shaft protrusion for the new nut. Removed the old nut using Harbor Freight electric impact, came off in a snap, was holding onto the pinion flange with just my hand. Replaced the seal - getting the old out was a major PITA. Started carefully tightening the new nut with the same electric impact driver, monitoring the pinion protrusion and rotational torque using my trusted fish scale. Exactly when both the target values for the torque and pinion protrusion were reached, the nut stopped moving. Guess I got lucky and my impact had just the right torque - the spec says 240 ft*lb (not that I bothered to look it up beforehand :) ). Got myself non-synthetic Lucas 85W-140, pouring it in, hope all is well now.

Cheers,
Alex

P.S. The dude in this video, https://www.youtube.com/watch?v=21962HlIKe8, didn't even bother to measure anything, just tightened the pinion nut with an air impact, which I am sure was more powerful than mine.
Author:  WWDiesel [ Thu Nov 29, 2018 10:02 pm ]
Post subject:  Re: Measuring rear diff. pinion rotating torque
You should be OK, good job! :BANANA:
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