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Discussion Starter · #1 ·
I just replaced a leaking pinion seal on a 67' 12 bolt rear end. Is there a torque spec. for the nut or do I just tighten it down snug?
Thanks!
 

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Just reading in Haynes here for you. It says pinion bearing preload is normaly between 15 and 30 lbs-in with new bearings and 10-15 lbs-in for bearings that have been in service
 

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This one is not as easy as it sounds. I agree that the preload needs to be about 30 inch pounds. That does not describe how tight the pinion nut needs to be however. EDLANTA there is a "crush" spacer between the two pinion bearings that when tightened properly gives you the proper bearing preload. Since you apparently didn't take any measures to "reference stake" the pinion nut you are now kinda in the woods for preload. Those crush spacers don't really like to be crushed twice. The inch pound figure describes the turning force in inch pounds that represents the friction of turning the pinion with an inch pound torque wrench with no other drag on the pinion ie: the ring gear assembly. You can try tightening the nut such that you have 30 inch pounds turning force or you can take the assembly apart and put a new "crush spacer" in and start over. I am not sure of what to advise you to do since I have my own way of replacing seals that I have had luck with over the years. I reuse the old spacer but my method is not for the uninitiated. You have to really be careful with this because improper preload leads to early bearing failure. That usually means ring and pinion failure too. Those gears don't usually forgive being run out of true after their mating pattern has been established. I guess you might as well try to retighten the nut now and pray for the best. DO NOT OVERTIGHTEN! If you achieve 30 in/lbs STOP! and reinstall the drive shaft and be happy.


If you ever do that job again first take a cold chisel and "stake" (make a mark) the pinion nut and the yoke (Companion Flange) so that you can put the nut back in EXACTLY the same place it was when you loosened it. That will reestablish the proper preload. I sure wish we'd talked before you started this project. Good luck

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1970 SS454 LS6 Chevelle, Damn! why did I sell that car?

[This message has been edited by charbilly2001 (edited 10-29-2001).]
 

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Shouldn't he have also counted the revolutions of the pinion nut coming off after staking it? I think that is also important but somebody please verify.

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65 Malibu SS, Crocus Yellow with black interior. Let the fun and back pain begin.
 

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ok good point. Let me clarify. On the last turn as you approach your stake mark it will get hard to turn. That is the point where you reestablish the origional preload. The stake mark at that point becomes the point you don't want to go past.
 

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You guys are really on it!

I learn something every day here.
Some of it I keep, and some I throw away.
This is a keeper.

Hope you didn't get Edlanta too bummed.

Dave

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<A HREF="http://nacs.net/~drunion/First_Page.html/
" TARGET=_blank>http://nacs.net/~drunion/First_Page.html/
</A> 69 Chevelle
454 .030 10.5:1
373 posi
M21 4spd.
12.30 @111 mph
License Plate:NTHE 12S
Me running a 12.63
 

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Discussion Starter · #7 ·
Oh Boy! What have I done?
If I understand correctly I need to tighten down the pinion nut sufficiently (However Tight)to create enough preload on the bearings to produce no more than 30lbs.in. resistance when turning over the assembly with an inch lbs. torque wrench? If this is correct will I need to disengage the axles or is the added drag minimal? How difficult is it to replace the crush spacer?
 

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Charbilly. Thanks for clearing that up. Sheesh! Am I glad you came back. I am taking my 4:10's out this week and puting in a set of 3:08's. Getting tired of gallons to the mile and want to get back to miles per gallon! I bought another complete rear end but it has 2:73's in it, and I do not want to go that high. I understand it is a good idea to put in a new crush when doing this. True or false? Thanks Terry
 

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edlanta now you know why I hesitated to tell you how this is done. You are already in the soup and I am trying to bail you out. The only thing you can do is tighten up the pinion nut pretty tight and hope for the best. It was all over as soon as you loosened up that nut without making a reference mark. If you wanted to be cautious and replace the crush spacer it would require complete disassembly ie: axle's out , carrier out , pinion out. Thats what I would do for insurance sake. Reassembly is no big deal since you can put the carrier back exactly as it came out. All depends on how convenient you want this deal to be. I hope you opt for a new spacer. I'd hate to see the pinion bearings fail over a spacer.

If you opt to replace the spacer be aware of the fact that preloading the spacer will take torquing the pinion nut to over 200 ft/lbs torque. I use a 1/2" air impact to do that but I also know what I am doing. My air impact will definitely over crush the spacer so I am very careful. If you have no access to an air impact wrench then this job can be ugly. Developing 200 + lbs of torque is no problem. Holding the companion flange in place while you are doing it certainly is. The tool companies make a jig that you bolt to the companion flange that allows you to counter torque while you tighten the nut but I am guessing you don't have one of those. A giant pipe wrench will also work nicely. You are going to have to be inventive. Put the business end of the pipe wrench on the flange with the other end of the pipe wrench on mother earth (this assumes you will be doing this job whilst laying on your back) and wrench away. Stopping frequently to check for that 30 in/lb rotating resistance. Good luck.

bcice......you are doing a full reinstall it sounds like. A much different deal. Yes by all means a new spacer is in order. Are you replacing the ring on your old carrier or are you swapping two already assembled carriers? If you are swapping rings on your carrier we need to talk. There are some tricks there too.

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1970 SS454 LS6 Chevelle, Damn! why did I sell that car?

[This message has been edited by charbilly2001 (edited 10-29-2001).]
 

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Wait a minute. 30 inch pounds is way too much preload for used bearings. About 12 is correct. Even new bearings don't get 30, only about 20 to 25. I don't think a new spacer is all that nessasary. Just tighten it as tight as you can get it with a 1/2 inch drive ratchet. You are not going to overtighten it that way. Clean the threads and put red locktight on them and use a new pinion nut. You did put some RTV sealant on the splines inside the yoke didn't you? Oil will leak out through them if you didn't. Did you put some RTV around the outside of the new seal when you put it in and did you lube the lip of the seal?

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'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drivetrain Parts & Service
www.lubedealer.com/biggearhead
 

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Thanks big gear head. I'm about to change out my seal too here soon and wouldn't have done those last three things you mentioned. Whew!!!!

By the way, are you a BIG BLUE FAN? I'm originally from Calvert City, KY just west of KY. Lake.

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65 Malibu SS, Crocus Yellow with black interior. Let the fun and back pain begin.
 

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The RTV suggestions from BGH are good. I will stand behind what I said about preload for new gears @ 30 inch pounds. Within limits tighter is better. Especially if the differential has to deal with major shock loads such as dragracing. I also agree that 12 to 15 inch lbs is correct for used bearings. If you follow my directions for staking the pinion nut and lining your stake marks up upon reassembly thats about what you will have.

Anybody that recommends that you have to replace old fasteners with new stuff everytime you do this kind of work is clearly spending somebody elses money. I have NEVER had a pinion nut failure and don't anticipate one in the near future.
Now lets not flame. We need to recognize thet there is more than one way to skin any cat.


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1970 SS454 LS6 Chevelle, Damn! why did I sell that car?

[This message has been edited by charbilly2001 (edited 10-30-2001).]
 

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Discussion Starter · #13 ·
Using a 1/2" Impact I was able to tighten down the nut enough to produce 12lbs.in. resistance of initial torque to get the assembly to start rotating. With the nut not quite as tight resistace was 3-5 lbs.in.
Should I leave it with the extra preload or loosen it up? Thanks!
 

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I'd quit while I was ahead. I think you are there. You agree BGH? See I AM willing to consult! lol

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1970 SS454 LS6 Chevelle, Damn! why did I sell that car?
 

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bcice......you are doing a full reinstall it sounds like. A much different deal. Yes by all means a new spacer is in order. Are you replacing the ring on your old carrier or are you swapping two already assembled carriers? If you are swapping rings on your carrier we need to talk. There are some tricks there too.

I bought another 12 bolt complete with 2:73 gears in it. I REALLY lucked out on that one. No drums or brake assembly on it but a guys wife wanted it out of the basement. $150.00. I am going to put the 3:08's into that rear and put it in so I can leave the one with 4:10's complete. I was originally going to put in 3:42's but I live so far from anywhere I take the chevelle I decided to go a little higher.I would have liked to try the 3:31's but they seem to be hard to locate. I believe both rears have the stage 3 posi unit as the 4;10's have a spacer. I have decided not to do this myself as it seems there are so many ways you can mess them up if not done correctly. A friend of mine is a mechanic and worked for a GM dealership for years.He has magnetic based dial indicators and all the good stuff for doing this correctly. I have some good info from big gear head printed out and am also going to print out this thread, and will be there when he does it.Good info from both you guys on here. Thanks!! Terry
 

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For anybody that might be contemplating replacing the pinion flange seal, the procedure is given in the Chevy shop manual and basically it says to measure the torque required before removing the flange and to reestablish that same value when reinstalling the flange. They say to mark the pinion and flange for reassembly in the same position. They say to use a new nut. New crush spacer not required. If you start messing with the bearings and new crush spacer and--heaven forbid--new gears, the job gets right out of amateur do-it-yourselfer territory.

My $0.02
 

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Discussion Starter · #17 ·
So this is what I've learned:
1) Post the question before picking up a wrench.
2) Wait a couple of days to compile replies and ask more naive questions.
3) Determine its out of my league and pay someone else to do it. (It's Cheaper)
Good thing us car crafters are filthy with the green stuff and can afford trashing big buck parts for the sake of knowledge!
Actually I've learned a lot about this subject and appreciate all replies. I've reset the preload to 12 inch lbs. and I think it will be fine. This is my 1st real project car and if it's worth keeping the rear end will be seeing more attention in the future!
Thanks!
ED.
 

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Glad to hear you got it.

Charbilly, didn't mean to come across bad. No flame intended. The reason I sugested a new nut is because I have had a problem with a used one backing off and I have seen a few others do it too. This is why I also use the red Lock Tight on them. When the nut backs off it usually ruins the gears. $3.50 for a new nut is cheap insurance.

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'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drivetrain Parts & Service
www.lubedealer.com/biggearhead

[This message has been edited by big gear head (edited 10-30-2001).]
 
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