Pinion Nut and Crush Sleeve - Second Generation Pontiac Firebird (1970 - 1981) - Firebird Nation

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Pinion Nut and Crush Sleeve


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#1 80Firebirdz

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Posted 3 weeks ago

Hey guys,

Im currently in the process of rebuilding my rear end on my 80 Firebird and I need HELP. Its an 8.5 inch 10 bolt. I purchased a kit that included new bearings/ seals, one Yukon Posi, two axle shafts, and 3.73 ring and pinion gears. I also purchased a disc brake conversion kit that Im installing after I finish the differential but thats an easy install. The problem that I have is how much Im supposed to torque my pinion nut. I torqued it to 60 foot lbs and I dont know if the crush sleeve is crushed. There are different opinions all over the internet because I saw somewhere that said 20-25 inch pounds to preload the bearings and somewhere that said 200 foot lbs to crush a new sleeve. I went with the opinion of 50-75 because at 20 inch pounds the threads of the pinion gear werent even flush with the top of the pinion nut. When I removed the original crush sleeve from the original pinion gear it didnt was not physically crushed or broken it was just slightly tighter than the new one. What should I do? What happens if the crush sleeve isnt crushed?

#2 myk74

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Posted 3 weeks ago

Do you have the pinion depth shimmed so that the wear pattern on the ring gear is correct? I believe the 20 inch pounds you are referring to is the amount of torque it takes to turn the pinion after all but the axles are installed, not the pinion nut torque.



#3 80Firebirdz

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Posted 3 weeks ago

I do not think that I have the pinion depth shimmed. How do I do that? I kind of mirrored the setup of the original pinion gear. After I removed the bearing on the pinion there was one small shim on the shaft. So I placed one small shim on the new one so that both would have the same configuration.

#4 80Firebirdz

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Posted 3 weeks ago

I dont know how much clearance the bearing should haveAttached File  E5DF946F-CD1A-4603-B2D3-B522AF24D4A2.jpeg   132.71KB   0 downloads
This is what it looks like with the differential temporarily placed in the housingAttached File  0A74C4C0-6B69-42BC-B842-377473115EEF.jpeg   100.69KB   0 downloads

Edited by 80Firebirdz, 3 weeks ago.


#5 JoePeek

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Posted 3 weeks ago

The inch-pound spec is how much rotational drag is on the pinion to turn it (without the ring installed)....when the correct bearing pre-load (crush) is OK, the inch-lb. reading is OK. The 200 ft-lbs. is a ballpark number that it will take to crush the sleeve. But how far you crush the sleeve you will have to check with a small inch-lb. torque wrench. If the pinion is still free spinning, tighten the nut a bit more and recheck the inch-lb. reading. When the pinion starts to get a little stiff to turn, you are getting close. If you go too far, you have to start over with a new crush sleeve. All this is just to get the pinion bearing pre-load correct. The other thing is how far away from the ring gear does the pinion sit. That is what that thin shim under the bearing does....it moves the pinion just a bit closer to the ring so the gears mesh right. Using the same shim thickness that the old pinion had is a good place to start, but you still need to verify the pattern on the gear teeth using some of that yellow pattern grease. So the pinion has to be shimmed towards the ring correct, and have the pinion bearing pre-load be correct. It doesn't hurt to have several crush sleeves on hand if this is the first time your doing this. Also, the carrier has preload and left to right position adjustment as well. Look on the internet at what a good gear pattern looks like and be prepared to assemble and disassemble everything several times until you get the pattern looking pretty good. Some guys think setting up a ring and pinion is an art, but really it is just having the right tools, like a magnetic stand with an indicator, an assortment of shims, and a whole lot of patience. 



#6 myk74

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Posted 3 weeks ago

I don't install the crush sleeve until I know the wear pattern is correct. Some people even hone out the bearing so that it's easier to remove to add or remove shims, I've never honed a bearing but have wanted to many times. Removing the bearing from the pinion each time you want to add a shim is a pain.



#7 JoePeek

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Posted 3 weeks ago

Yes, I've done the crush sleeve at the end as well, I even replaced the crush sleeve with a solid shim set one time, but was a pain to get the stack to come out right on the money to get the inch-lb rotation to be somewhere in spec. It is tempting to hone the bore rather than have to take off the bearing, without wrecking the roller cage.



#8 80Firebirdz

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Posted 3 weeks ago

Before I install the axles and ring gear, I want to make sure my pinion is installed properly. I dont know the depth that it should be prior to installing the gear. Is there a place I can find that information?
Should I keep the pinion where it currently is and install the ring and axles to check the preload bearing. Then I can test the pattern or backspace by adding/ removing shims right?
I have a dial indicator and some grease

#9 JoePeek

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Posted 3 weeks ago

You need to check the pre-load (in-lbs. of rotation) without the ring installed. There should be some numbers scribed on the face of the pinion, but unless you have a depth mic and a fixture to locate it from the correct datum, you really won't be able to actually measure the pinion depth. It is worth a good chance that by using the same shim that was under the old pinion bearing you may be OK, at least it's a good first guess. I would install the new outer races, install the pinion, without the crush sleeve as mentioned above (just snug it to zero clearance between the inner and outer bearing). Then install the carrier, using the same shim stack on each side that was in the original set up. Actually, I like to trial fit the ring/carrier before I install the pinion, then I can free spin the carrier by itself so I can feel that it rotates a few turns if I give it a spin, but has some pre-load that makes it stop in a few turns. At least then I know the total shim stack of both sides. If I have to take some shims from one side over to the other side later to move the ring left of right, at least I know how much total shims I need to keep the overall carrier pre-load. Then I put everything together an take the first pattern reading and shift the carrier a bit to get a good pattern, hopefully I can get a good pattern by just moving shims from one side of the carrier to the other and not have to mess with the pinion shim....but sometimes you have to take out the carrier, and shim the pinion in some cases.



#10 JOE68

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Posted 3 weeks ago

if you do not get the gear mesh depth correct it will destroy the gears when you drive it



#11 80Firebirdz

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Posted 3 weeks ago

Thank you for the helpful info. I just got some new crush sleeves and an inch pound torque wrench. Im going to remove the pinion nut and the crush sleeve, remove the ring gear from my carrier, install the pinion without a crush sleeve and torque it to 25 inch pounds of rotation. I dont fully understand how to measure the rotational drag of the pinion but Im assuming I set the torque wrench to 25 and turn the nut until it clicks and then rotate it one full rotation? After that I will install the ring gear on the carrier and add shims between the bearing and the axle to make the carrier and ring fit snug. I know its taking me a while to fully understand the process but this is my first time. Am I on the right track?

#12 JoePeek

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Posted 3 weeks ago

I do not use a clicker inch-lb. torque wrench, I use an old school beam type torque wrench. Reason is that with a clicker you can still rotate the pinion even after it clicks at 25. I guess if the nut rotates before it clicks at 25 then you know it is somewhere less than 25, but how much less? If you reset the wrench to 20 and it clicks before it rotates, then you can say it's in between 20 and 25, and that may be within spec, so you could make the clicker get you by, but a beam type you can just read the scale directly while it's turning to get the exact number straight off the scale. Remember, you are not measuring how tight the nut is, you are measuring how hard it is to rotate the pinion. As you tighten the nut and crush the sleeve (using a long breaker bar or cheater pipe), the two bearings are getting closer together. If you stopped tightening the pinion nut just right when the all the backlash slop was just barely taken out, you could give the pinion a spin and you could drink half a beer before it stopped freewheel spinning, this is too loose. You need to take out the slop, and then go a bit more so the bearings are squeezed together just a little. But how much is "just a little" ? If there is too much pre-load the bearings can run hot and gall the races and rollers. If too loose, then they make noise. especially when you let off the throttle, and the gear pattern won't hold if the pinion is moving around. So the trick is to pre-load the bearings, but not too much, and the pre-load amount is related to how hard it is to rotate the pinion. That is where the inch-lb. reading comes into play. There is really an upper and lower limit for what's acceptable rotational torque to verify the pre-load is sufficient, but not too much. As far as the carrier goes, I pre-fit the carrier/ring assembly before I install the pinion. You can't feel the rotational drag of the carrier to verify sufficient carrier bearing pre-load if the ring gear and pinion gear teeth are meshed together. Also, mark the bearing caps (top and bottom/left and right side) that hold in the carrier so you can put them back on the same way they came off. 


Edited by JoePeek, 3 weeks ago.


#13 80Firebirdz

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Posted 2 weeks ago

Thanks for all of the help and assistance. I was finally able to install everything. My final question is about the torque value of the rotational drag after everything is installed. The pinion pre load alone measured between 20-25 inch pounds. But after I installed the carrier, ring gear, and axles, its measuring between 45-50 inch pounds. My backlash is perfect at .007 and my pattern is great. Is this 45-50 inch pounds a reasonable amount for the final product?

#14 JoePeek

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Posted 2 weeks ago

Looks like you're good to go. The pinion inch-lb's are going to go up when everything is together because now you are also turning the carrier & axles, which is going to make more rotational load/drag and the torque number will naturally be higher. The pinion rotation in.-lb. spec is for rotating the pinion by itself before you install the ring/carrier & axles.



#15 greywolf224

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Posted 2 weeks ago

I rebuilt my first axle over this past winter. I did a lot of reading and watched a bunch of videos and downloaded a lot of documentation that taught me how to do the rebuild along with all the specs I needed.
I made sure I had a few crush washers but honest to God I needed to use just one. I figured since I saved the money on a rebuild I would buy myself a few decent tools one of them being a really nice inch pound torque gauge which made it extremely easy to measure the preload. I used 4 foot pipe wrench and a 4 foot breaker bar to set the proper crush depth. It was very slow going until I got it just right.
It actually took me 12 times to get the carrier shims and gear pattern just right. I did have my old set of pinion bearings and I honed them out Slowly until they perfectly slid on and off the pinion gear which was a big time saver.
My ring gear run out was about 2 thousands on the high side but no matter how many times I reset it it always remain the same. Some folks would return the gear set I chose not to. The other setting that was off was actually the axle play which was around 12 thousandths again on the high side. But what do you want from 40-year-old axles. I change the c- clips but it didn't help any But decided to go with it and see. Great experience in learning how to rebuild that axle. I have about 1700 miles on that axle and it sounds great with no chatter.






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