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Author Topic: Rockwell differential bearing pre-load?  (Read 3276 times)

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Offline BOBWOOD

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Rockwell differential bearing pre-load?
« on: October 14, 2011, 09:28:50 pm »
Hi all...just wondering if someone can give me some advice on how to properly preload the bearings on a Rockwell pr-61-NX18 differential...which is on my 1964 215 Timberjack skidder (now a forwarder)...unfortunately we ended up taking it all apart but just not sure how much we should tighten the adjustment rings on reassembly. BOB

Offline smwwoody

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Re: Rockwell differential bearing pre-load?
« Reply #1 on: October 15, 2011, 07:52:06 am »
New Or used bearings?
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Offline shelbycharger400

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Re: Rockwell differential bearing pre-load?
« Reply #2 on: October 15, 2011, 09:13:59 am »
not shure which bearing your tightening, i have never had one of those apart
standard truck diff's,  setting correct torque on the pinion nut of around 250 ft lbs with the correct shims yeilded turning torque of 6 ft lbs,  side bearings i set them up, left first to bring in the gear within a few thousandths of correct contact, torqing right, checking nesting pattern with prussion blue.  75 ft lb torque on the side bearing nuts.

http://www.rockwellparts.com/

Offline mad murdock

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Re: Rockwell differential bearing pre-load?
« Reply #3 on: October 15, 2011, 09:56:58 am »
Shelbycharger's description is a pretty good explaination of what you want.  I have not rebuilt a diff. on a skidder, but the principles involved are the same on any diff. shimming the pinion for correct rotational "drag torque" is important, if it is too little, you will have premature bearing failure, and if it is too tight, you will result in  heat buildup at the bearings and they will fail as well. Make sure when you are checking the rotational drag on the pinion that you have some oil on the bearings, there is a big difference on rotational drag between wet and dry bearings. The correct contact pattern needs to be checked with layout dye, (dykem, or prussian blue_).  You want the contact area to be center top to bottom on both the pinion and ring gear teeth, and to be slightly toward the center of rotation on both gears, or toward the "toe" of the gear tooth.  Shims need to be adjusted as required for proper gear tooth contact.  If you are looking at the gears as they were removed, unless you had to change parts due to being badly worn, you should be able to see where the contact pattern was before, and re establish it in the same area. finally be sure an check for proper backlash, (free movement between the 2 gears with no contact), should be a few thousaths of an inch.  I am not sure of their precision spec, but guessing on a range of .004"-008" Maybe a forumite will be able to link you up with the exact procedure from the rockwell manual.  Good luck, http://www.precisiongear.com/pgtechpatterns.htm
 this link shows some pictures of what I am trying to describe for gear tooth pattern.
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Offline HuZzEy

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Re: Rockwell differential bearing pre-load?
« Reply #4 on: October 15, 2011, 07:04:15 pm »
are you talking about carrier bearings if you are you need the measure ring to pinion clearance also I also have never rebuild an axle on my skidder but I rebuild alot of rockwell truck axles and all bearing clearances are 1 to 3 thousanths ring and pinion clearance same

Offline shelbycharger400

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Re: Rockwell differential bearing pre-load?
« Reply #5 on: October 15, 2011, 07:13:08 pm »
mad murdock is right on the 4-8 thousandths.
here is an odd thing for u to know.... set a dodge or chevy up.... very little backlash...its right, ford... a little backlash...its right.
dont forget when you do find the correct torque... put a rag around the pinion yoke, turn and check pattern...gives a loaded pattern...yes it will be different otherwise

Offline smwwoody

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Re: Rockwell differential bearing pre-load?
« Reply #6 on: October 15, 2011, 07:15:08 pm »
Yea what SC 400 said.  You will want a little less preload on used bearings than new ones.  When you check the preload on the pinion bearings do it without the carrier installed and make sure they are well oiled it makes a big differance like mad murdock said
Full time commercial logger
Franklin 170 grapple
Franklin 5005 feller buncher
Barko 275B  W/ctr delimber & ctr slasher
Prentice T325 W/ctr delimber & CTR slasher
international 4900 triaxle W/ Prentice telestick 33
Dazco delimber
Mack R model road tractor
4 husky 372s and a junk 576
KJ4WXC

Offline BOBWOOD

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Re: Rockwell differential bearing pre-load?
« Reply #7 on: October 15, 2011, 07:34:26 pm »
Thanks for all the help guys! I know my father has done this before but not for a while and likely never on Rockwells...yes I guess I am most concerned with the pinion bearings...and getting those notched adjusting rings with the special elongated eye cotter pin...to the right torque... they are actually the old bearings...not new ones. I wish I didn't need to learn this right now but I guess I do! BOB

Offline kiko

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Re: Rockwell differential bearing pre-load?
« Reply #8 on: October 16, 2011, 10:46:40 am »
I am sure this is not by the book, but has worked for me many times. I set pinion preload in the shop press by using a piece of pipe to press bearing toward each other intsead of having to put yolk and pinion nut on and off each time till I get it right. When pressed the pinion housing should turn with slight drag. Adding shims between bearings will loosen and removing will make it tighter. Even though you do not have shims on a wheel splindle , it is the same principle. As far as carrier bearing preload, After pinion has been set and installed into diff housind set ring gear and start adjustment nuts . Tighten toward each other untill they tighten up. This needs to be done with ring gear not all the way into the pinion gear so you can feel the preload on the carrier bearings. Once you have gotten slight drag you must bring ring gear into pinion. Loosen one nut two notches and tighten other other one two notches. ( does not have to be two just do it evenly)to move ring gear closer to pinion. Back lash can now be measured or by feel . When you rock the ring gear back and forth with ou moving the pinion the should be a slight bump that you can feel but hardly see. I use red grease to check run out. place a grease on ring gear and roll through pinion. Then you can see how your gears mate up. I hope I was able to convey what is in my head. OH yea, you can make additional pinion shims out an alum can.

Offline BOBWOOD

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Re: Rockwell differential bearing pre-load?
« Reply #9 on: December 06, 2011, 04:04:58 pm »
Hi all...just going to add some photos to this post so everyone can benefit from them when doing a search. I have the old Rockwell axles with the 3 brass pins discussed in many posts on FF. Mine are Pr-61-NX...but basically the same as the 50s etc.