Slant Six Forum :: D150 rear gear change, the rest of the story

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D150 rear gear change, the rest of the story https://slantsix.org/forum/viewtopic.php?t=60033	Page 1 of 1

Author:	DadTruck [ Thu Aug 11, 2016 3:08 pm ]
Post subject:	D150 rear gear change, the rest of the story
well,,, what doesn't kill you just makes you stronger ,,, right,,, I certainly hope so. 250 miles into the break in, the pinion shifted and ran into the center spider housing,, fortunately the issue developed while I was about 4 miles from home, ( no trailer) was able to drop the drive shaft,, re set the pinion nut and get back home,,, photos: https://www.flickr.com/photos/13718356@ ... 9268325243 when setting the pinion torque to turn,, Dennis and I followed the instructions that came with the Yukon gear set,, 'pinion bearing pre load 12 - 15 inch lbs with new bearings, with no final pinion nut torque requirement' we had the pinion pre load at 15 inch lbs using a new certified torque gauge, at the time Dennis had 75 ft lbs on the pinion nut,, we though that was low, but went with that as it was in line with the Yukon instructions. upon further review the FSM specifies '20 to 35 inch lbs for new bearings AND a minimum of 210 ft lbs on the pinion nut'. I contacted Yukon Tech help line today, per Yukon there is no need for a minimum torque as if the 12 to 15 inch lbs of pinion pre load was achieved the resultant torque on the pinion nut would be in the 300 to 400 ft lbs range. the Yukon tech believes one of the pinion races was not fully set and that resulted in the pinion moving,, I don't think so as I saw Dennis strike the pinion square and full on each end then we re checked the pinion pre load and it had not changed. The Yukon tech also stated the FSM spec of 20 to 35 inch lbs of pre torque was excessive, would heat the pinion bearings and burn the diff oil,,, obviously there is some difference between the Yukon and Chrysler FSM pinion bearing settings.. anyway, I disassembled the differential today,, much debris from the pinion to spider gear housing contact. I reset the pinion nut to 75 ft lbs and the pinion torque to turn was 25 to 30,, with lots of effort required to get the pinion to turn ( on my job we called that 'stiction', and no smooth turning during the rotation. I think the pinion bearings are full of debris,,, there were particles from the spider housing 1/8 inch long and paper thickness thick in the diff fluid,,, like machining chips from the pinion contacting the spider gear housing,,, so cutting to the question,, from folks that have rebuilt 8.25 diffs,, follow the FSM for pinion pre load? 20 to 25 inch lbs and 210 nut torque? any other tips? after I reset the pinion nut torque to 75 ft lbs I re checked back lash and the ring to pinion contact, backlash was .006 , as it was when set initially and the contact patches were as I remember seeing them, thanks

Author:	slantzilla [ Thu Aug 11, 2016 4:00 pm ]
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Does the pinion move smoothly after breakaway, or does it feel rough? There may possibly be junk in it. Next time I do Yukon gears the book is going in the trash.

Author:	DadTruck [ Sat Aug 13, 2016 5:52 am ]
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Disassembled everything out of the rear housing,,, washed- blowed off - and washed again the rear pinion bearing sets,, they had a lot of debris in them,, a silver miner would have been thrilled with the quantity of tiny silver colored flakes that washed from the bearing sets. oiled the bearings and re assembled the pinion,, at 75 ft lbs of torque on the pinion nut,, the readings on the inch pound torque dial were as I remembered seeing them during the assembly process,, with the pinion in rotation the needled would center around 15 inch lbs but would also sweep from maybe 22 to 8. I continued to add torque to the pinion nut in 20 ft lb increments and the readings on the inch lb torque dial did not change significantly,, until the point where 185 ft lbs was on the pinion nut,, at about that point with the pinion in rotation the needle sweep of the inch lb dial became centered on 7 lbs and the range decreased to 5 to 9. Took the pinion nut torque up to 205 and the bearing preload increased to 8 to 9. Took the pinion nut torque to 225 and the bearing preload remained at 8 t 9. I believe the root cause of the failure was a misinterpretation of the values on the inch lb torque dial. That misinterpretation resulted in a low torque condition on the pinion nut. For what it is worth,, I did extensive internet searching for pinion bearing preload for 8.25 axles,, everything I found agrees with the Yukon 12 - 15 in lbs for new and 6 - 8 inch lbs on used bearings,,I do believe there should be guidance on a minimum torque for the pinion nut. For that I used the FSM 215 ft lbs. with 250 miles on the pinion bearings the torque to turn requirements look to fit on the low end of new and the high end for used bearing sets. I'll bump the pinion nut another 20 ft lbs and see if the torque to turn for the pinion changes. Then, strip everything out of the rear housing and clean the internal surfaces to remove the metal particles, then put it back together.

Author:	DadTruck [ Mon Aug 15, 2016 3:52 pm ]
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https://www.flickr.com/photos/13718356@ ... 2504096285 received the replacement 8.25 center section care package today,, much thanks,,, also figured since I was going to be spending the next day or so under the '83 D150 rear axle, might as well get comfy and install an Air Lift package to level out the truck when towing,,

Author:	DadTruck [ Mon Aug 22, 2016 5:38 pm ]
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https://www.flickr.com/photos/13718356@ ... 1622740720 finished the diff reinstall today,, used a much different process for torquing the pinion nut compared to how it was torqued on the first re assembly,, lubed the new pinion bearing races with gear lube, new crush sleeve,, set the pinion assembly into the housing,, used ARP bolt lube on the washer and nut face, and put a few drops of Red Permetex loctite on the pinion threads. Torqued the pinion nut up to the FSM low limit spec of 215 Ft lbs in 50 Ft lbs stages, stopping the spin the pinion in both directions at every interval, checked pinion in lb to turn with 215 Ft lb on the pinion nut,, was maybe 2 in lb,, ran the pinion nut torque up in 15 ft lb increments and checked pinion in lb to turn at every stop. it was at my torque wrench 250 ft lb max that the pinion bearing preload finally started to move,, got to 5 in lb,, using a breaker bar with a 3 ft pipe extension on it,, with about three more good hard pushes, and checking the pinion bearing preload between each push,, the pinion pre load was at 13 to 14 in lb,(spec 12 to 15 in lb) , I am estimating that the pinion nut torque is around 275 ft lbs. The needle on the inch lb torque wrench was really steady, much different from the first install, Backlash came in without much issue,, rechecked the gear mesh,, I wanted it in a bit deeper so I had added an additional .003 to the pinion shim. I can see the change and the gear mesh pattern looks fine. With new pinion bearing and new carrier bearings, I went ahead and changed out the axle bearings. They have around 150K miles on them. The axle bearing run areas looked fine so I went with new OE style bearings. And as previously mentioned while I was under the truck, I installed a set of Air Lift bags,, That install was very straight forward, I was able to use an existing frame hole to match up with the upper brackets, so I only had to drill three holes per side,,every little bit helps,, Here is a article that discusses the history behind Air Lift,, http://www.speedhunters.com/2014/05/kno ... uspension/ I strongly remember see the Air Lift decals on about every Nascar stocker in the 60's and 70's,, it was probably a major suspension tuning tool,, prior to having the 'Race Shock Absorber Engineer' position that is common today. So the D150 is back on the road,

Author:	slantzilla [ Mon Aug 22, 2016 6:46 pm ]
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Wooohoooooo!!!!!!

Author:	Charrlie_S [ Tue Aug 23, 2016 5:00 am ]
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Kool beans. So your now ready for Clay City, right?

Author:	DadTruck [ Tue Aug 23, 2016 12:30 pm ]
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yes,, Clay City

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