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Pinion bearing preload and gear mesh

Littlered89

Littlered89

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Hey everyone, I got another question. This is my first time rebuilding a diff.

1989 d100 8.25

I am replacing everything (gears, crush sleeves, bearings, and seals)

I looked in the Haynes manual but its not very clear and I have looked online and none of it makes a lot of sense to me.

I am wondering the correct way to set the pinion preload and how exactly it is supposed to be torqued.

Also the backlash in the ring gear (.007-.010) is what I have heard, not sure if that's correct or not.

One more, the torque on the carrier bearings, I've heard 70ft/lbs with the position of it in the correct place.

Just incase.. I got 3.55 gear set and I'm not building a hotrod. Maybe a little power later but daily driver for now.

If there is a link to the correct way please post that and I really appreciate all the help you all have given me so far.
 
There should be something on the net about it. That kind of info is for just about everything else. If this is your first time, it's a good idea to have someone 'guide' you though so you don't make any expensive mistakes. Also, it makes things a lot easier if you have 'trial' bearings to get your settings before installing the permanent bearings. If you have to pull one off, you usually ruin it unless you have the proper pullers etc. And I'm not sure about 70ft/lbs with the position of it in the correct place means? With adjustable rears like an 8 3/4, I snug them up pretty good but don't have a way to check how much 'preload' they have like you can check on a pinion bearing preload.
 
I just mean if the carrier is correct side to side so the mesh is right and the bearings should be torqued to 70. I don't know. I do have a Chilton manual on the way I hope that will help. Not sure if I have a trial bearing but I do have 2 crush sleeves.
 
Littlered89 said:
I just mean if the carrier is correct side to side so the mesh is right and the bearings should be torqued to 70. I don't know. I do have a Chilton manual on the way I hope that will help. Not sure if I have a trial bearing but I do have 2 crush sleeves.
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Littlered89 said:
Not exactly sure what the bearing caps are supposed to be on the 8 1/4 since I don't know what size the cap bolts are but there are charts for the size of bolt that's used on them. If the thread size is 7/16ths, then the torque is right at 70....
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Yeah that is weird. I'm mainly confused by the rolling torque and then crank it down to 210 ft/lbs. I assumed the rolling torque was the preload and wouldn't the 210 mess that up?
 
Littlered89 said:
Yeah that is weird. I'm mainly confused by the rolling torque and then crank it down to 210 ft/lbs. I assumed the rolling torque was the preload and wouldn't the 210 mess that up?
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Rolling torque on the pinion nut....well, I go by what the rolling torque is on the bearings and don't worry about the stated nut torque but I do use red Loc-tite on the final assembly. Once I get the rolling torque without the seal, I mark the nut in relation to the pinion and go back to that on the final torque and then check the rolling torque again. It should be at least the same if not a few pounds more.....and that's using the 'new' pinion nut on the final assembly. A used nut will give up torque when reused and get pretty bad after several torque sequences. Many do not realize that or chose not to believe it but I've seen it in testing....
 
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Ok so set the rolling torque, mark it, disassemble and reassemble with new seal and lock-tite on the pinion nut threads?

I just checked and I do not have extra bearings. I do have 2 seals and 2 crush sleeves.

I just really want to do this right so it can be my daily driver again.
 
Littlered89 said:
Ok so set the rolling torque, mark it, disassemble and reassemble with new seal and lock-tite on the pinion nut threads?

I just checked and I do not have extra bearings. I do have 2 seals and 2 crush sleeves.

I just really want to do this right so it can be my daily driver again.
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If you have the right pinion depth, no need to install a new set of bearings....but I always finish things with a new pinion nut.
 
Littlered89 said:
How do I know if the pinion depth is right?
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Well, one way is to check the pattern with white or yellow grease. I have pinion depth tool that tells me......both methods require a set of trial bearings that slip on and off easily.
 
Oh. Ok. Well as much as I hate to say it I guess I should take it in. I hate paying for something I can learn to do but everyone I know says pound it on with an impact and I know that's not the right way.
 
If it has a crush sleeve it is not supposed to be reused. To me torqueing the pinion nut one time makes it used. Is that not correct?
 
7mopar said:
If it has a crush sleeve it is not supposed to be reused. To me torqueing the pinion nut one time makes it used. Is that not correct?
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Most instructions say to set pinion bearing preload without the seal in place. Always thought that was odd because of the crush sleeve. The 8 3/4 '89' case sleeve has some 'spring' to it and I have reused them but just didn't tighten the pinion nut to the specs stated....and use Loc-tite on it to make sure it doesn't have any chance of loosening. I've never had a problem doing it that way but over the years, I started using a solid spacer in them and set up like it's a '42' case with shims to set pinion bearing preload.
 
Littlered89 said:
Oh. Ok. Well as much as I hate to say it I guess I should take it in. I hate paying for something I can learn to do but everyone I know says pound it on with an impact and I know that's not the right way.
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I borrowed a pinion depth checking tool that a friend of mine bought and only used it one time to set up a Dana 60. I was there to help (mostly watch) and that was my introduction to gear swaps. A few years later after setting up a successful 4.10 people asked me who did it for me and once I said "I did it myself".....next thing I know I'm in business lol. This was happening before the internet! If you think you might set up more than one, dive on in. It's a whole lot more easier now with all the info available on the net. As for the tool, my buddy didn't want to sell it but he said to just hang onto it and about 10 years later he asked if I still had it. He knew I'd been setting up rear ends and told him yep.....and that's when he said 100 bucks? I was happy to pay that because to me it was worth it plus they cost more than that even when he bought it plus the tool had proved itself many times.
 
Even if I'm not doing it all the time I'd still like to know how so if I ever have to do it again I'll know. I'll look for that tool. Are they make specific or universal for all makes and models with a diff?
 
All pinion I have set had the depth stamped in the big end. Not sure if it is on the crush sleeve ones that are set by torque and spin test. Have often wondered why the check tool could not be made from pipe section. Extra heavy pipe and a lathe should do the job.
 
I am a manual machinist. Can you post a picture of the depth tool you have when you have time please? I might be able to make or just buy one. I'll check the new and old pinion gear when I get home from work to see if there is a depth stamped on one of them.
 
Old gear has 350/917-3.90 stamped on the side and nothing that makes sense to me on the top. New has I'm guessing manufacture numbers and that's it.
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