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Author Topic: Differencial yoke nut torque?  (Read 4457 times)
lostagain
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« on: February 27, 2009, 06:55:28 AM »

The 4-71 DD is out of my Courier 96 for an overhaul. (See "Engine tune up advice" thread). I am fixing all the leaks. Replacing oil seals and gaskets along the line from front pulley to diff. I had the diff. out and replaced a couple of gaskets and the oil seal. BTW taking the diff. down is a big job. Putting it back up into the pumpkin is a BIGGER job. It weighs about 300 lbs. I borrowed a ATV lift and that helped a lot. I had to jack the bus up an extra 6 inches to get it past the frame/bulkhead. Anyway, the question today is how much torque should I apply to the nut that holds the yoke onto the pinion/input shaft. The yoke pushes against a big cone needle bearing. I understand it has to be at least snug so the pinion shaft is held up straight and the gear teeth mesh nicely. The shaft is 1 and 1/4 inch diam. The threads are finer than NF. It is a Rockwell. Thanks.
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JC
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« Reply #1 on: February 27, 2009, 07:09:40 AM »

JC, what size is the nut Rockwell list 10 different torques for the nut depending on the size from 
 200 ft lbs to 1200 ft lbs.oops sorry didn't read all of it   
1.25 x 12   700-900 ft lbs
1.25 x 18   700-900 ft lbs  
good luck    
« Last Edit: February 27, 2009, 07:14:54 AM by luvrbus » Logged

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« Reply #2 on: February 27, 2009, 07:13:25 AM »

When I did the same thing on my 06 I had to buy a special socket and the torque was 600 lbs. foot.>>>Dan
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« Reply #3 on: February 27, 2009, 07:22:24 AM »

It is 1.25"X?. I'll have to count the threads. I'll get back to you with it later this morning.

JC
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JC
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« Reply #4 on: February 27, 2009, 07:40:30 AM »

Funny you should ask about the torque on the pinion nut. we replaced the outer pinion bearing last fall on our 4106 and according to the GM book the torque spec is 1100 foot pounds. anyway we used a 3/4 inch drive air impact to tighten the nut and went on a 3500 mile road trip. well that stupid nut came loose at about the 3000 mile mark so I stopped at a truck stop and changed the lube checking for metal in the old oil there was none.

after getting home we removed the whole assembly and took it to a qualified rebuilder to let the pros fix it this time. turns out the pinion nut came loose I must not have tightened it enough, the repair shop told me they do not torque that nut with a  gauge wrench either their method is to use a 1 inch air gun until it is not turning. so there you have it a shop that rebuilds thousands of rearends every year and no torque wrench ?

we shall see

Chris   
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« Reply #5 on: February 27, 2009, 07:42:10 AM »

Another consideration is to get the torque as close as possible and still line up the cotter ket slots.>>>Dan
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« Reply #6 on: February 27, 2009, 07:54:34 AM »

Hi JC,
When a friend (he's a retired bus mechanic) and I replaced the pinion seal on my GM 4106 we used a short pipe on my 3/4" drive ratchet handle and a 3/4 ton come along between the pipe and the suspension frame to tighten the nut. We were working in my pit so had plenty of room to work. I don't think either of us had the strength to get it tight enough any other way with the tools we had to work with. We used a wheel bearing socket and deformed the 3/4" square hole in it, but it worked.
Good luck with your project, Sam 4106
Chris, did you put the cotter pin back in when you tightened the nut? I sure don't know how the nut loosened up if the cotter pin was in.
Thanks, Sam 4106
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« Reply #7 on: February 27, 2009, 08:01:21 AM »

Yes we installed the cotter pin But we think the nut just was not tight enough to begin with

Chris
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lostagain
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« Reply #8 on: February 27, 2009, 09:02:00 AM »

The shaft has 22 threads to the inch. I borrowed a 1 and 13/16th inch socket for the nut, and I will tighten it with the 3/4" air impact wrench. Or should I borrow a 1"?

JC
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« Reply #9 on: February 27, 2009, 09:24:22 AM »

JC, it is 800 to 1000 ft lbs     

good luck
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« Reply #10 on: February 27, 2009, 09:27:24 AM »

JC,

 Think you should borrow the 1 in gun. 400 lbs is right at the human limit by hand. Guess you could try a 1 in socket set and a 15 foot pipe. I have 2 models of 3/4 Ingersol Rand guns, the best being the composite model and they don't hit anywhere near hard enough for a pinion nut. A cheap 1 in is not much better, so look for an IR if you can get one.
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« Reply #11 on: February 27, 2009, 09:30:20 AM »

Hi Dan,
I just looked up the torque spec. in the maintenance manual for my GM 4106 and it is 800-1100 foot pounds for the propeller shaft flange nut. I'm surprized that yours is 600 foot pounds. Would you please verify that.
Thanks, Sam 4106
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« Reply #12 on: February 27, 2009, 10:57:06 AM »

800 to 1100 ft-lbs according to my manual for a PD4501.

I don't like the beating an impact wrench puts on the bearings. It will reduce the bearing life, but I don't know by how much.

This is a perfect application for a torque multiplier. A possible excuse for a new tool?  Grin    It can be used elsewhere too. . .  Grin
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« Reply #13 on: February 27, 2009, 11:12:28 AM »

When replacing pinion seals mark the nut with a scribe and when reassembling make sure the yoke is indexed in the same position as before and tighten the nut to the same position as before.  Some pinions have a crush washer to set bearing preload and you can not tighten to the original torque unless replacing the crush washer.  If the preload is set by shims then you should tighten to the specified torque.  Using a air wrench will cause indentions in the gears and can lead to ring and pinion gear failure.  My take as always not worth much.  john
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« Reply #14 on: February 27, 2009, 12:15:30 PM »

Sam, I did mine eight years and 20K miles ago and no problems since.>>>Dan
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« Reply #15 on: February 27, 2009, 12:25:59 PM »

I don't see a crush washer. There is a big spacer between the bearings. I just called The Gear Center in Calgary, and their service manager told me they use a 1" impact wrench and hammer away. Does it damage the gears? No he says. Maybe they like to sell gear sets...
I didn't mark the position of the yoke when I took it off the shaft spline. I hope it doesn't create an imbalance issue, assuming that's what you were refering to, Junkman.

JC
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« Reply #16 on: February 27, 2009, 02:50:02 PM »

JC, you have no crush washer only the spacer between the bearing to keep from binding the bearings   good luck
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« Reply #17 on: February 27, 2009, 03:00:57 PM »

Hold the nut firmly in the direction of turning to minimize "slapping" of the gears.>>>Dan
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« Reply #18 on: February 27, 2009, 04:05:51 PM »

This is a very important spec, now is the time for you to consult the maint manual. There is no substitute for the correct info - this is no time for guessing.

This thing takes an incredible amount of torque, even my little slant six Plymouth took 250 lb-ft.

You can do this with even a small torque wrench if you have a long enough lever. Note what other posters have said about using pipe extensions.

Essentially what you do is use your torque wrench at the end of a long pipe or beam, the longer the better. Then you compute the amount of torque you need to read on the wrench, it will be way below the actual torque at the nut. The longer the extension the less the pull at the end.

Works like a charm if you have enough space for the long extension and even a wimp like me can tighten it!
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« Reply #19 on: February 27, 2009, 05:10:39 PM »

Gus, correct Me if I am wrong!  wouldn't the extension have to be between the drive end of the torque wrench and the socket thus multiplying the torque applied?  There is a chart supplied with some high end wrenches for this purpose.  john
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« Reply #20 on: February 27, 2009, 07:54:02 PM »

I think that was what Gus was saying, but stop and think of how much did it take to remove?? and its probably been on there a long time.>>>Dan
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« Reply #21 on: February 27, 2009, 08:05:59 PM »

You guys can't put an extension on a torque wrench. Its improper use of the tool and won't do it any good at all. I never have used my 600 lb 3/4 Torque Wrench to loosen bolts, it only gets to tighten bolts. It is a specialty precision tool and thats its only job.

If you use a cheater pipe you will have to find a 1 inch socket set (breaker bar) because a 3/4 will bend before you get close. There is no practical way to hand torque this nut. The practical way says IR on it and looks like a tire gun.

Don't beat it up to much with the tire gun, I have seen them snap off just behind the nut.
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Gold is the money of Kings, Silver is the money of Gentlemen, Barter is the money of Peasants, Debt is the money of Slaves.

$1M in $1000 bills = 8 inches high.
$1B in $1000 bills = 800 feet high.
$1T in $1000 bills = 142 miles high
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« Reply #22 on: February 27, 2009, 08:29:05 PM »

Great discussion guys! Ah, the art of bus maintenance... The gear set assembly is back in the pumpkin, nice and snug. I don't really want to take it back down to hand torque the yoke nut. It was major effort to get it up and lined up to slide back in. At that time, I thought I would leave the yoke and nut till after, because it adds a good 4 inches to the end of the shaft, and the space is limited between the axle and the bulkhead. There is not much space under the bus for extention pipes. And as has been pointed out, it would take a 1" drive breaker bar to do it. So, I will use the 1" tire gun, and hold the shaft firmly in the direction of turning to minimize the slap on the gears, and take my chances.

Thanks for all the suggestions and ideas. This board is so great!

I'll keep you posted about my engine overhaul.

JC
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« Reply #23 on: February 28, 2009, 01:59:27 PM »

I said use the wrench at the end of the extension and I should have said at the pulling end, again, sometimes I'm not too clear! Yes, it cannot be used at the nut end unless it is a high capacity torque wrench. I meant that an extension can be used with a small wrench for high torque jobs.

However, it is not a good idea to ever use a pipe extension on the handle of a torque wrench even if it is a high capacity one. This is a good way to destroy the wrench calibration. An extension is always better.

There is absolutely no reason not to use a torque wrench at the end of an extension. The torque wrench doesn't know the difference because the torque on it is the same regardless. This can be done with any torque wrench regardless of price.

I don't think anyone said anything about removing nuts with a torque wrench. I think most people know better than that. The amount of torque required to remove a nut is not the same as the torque used to install it. Removing normally takes much more torque than installation, especially if it is rusted or jammed for any other reason. Never use removal torque as a guide for installation.

I don't think I would ever use an air wrench to torque a nut unless the air wrench has a very good torque limiting control. Some have controls but I find that most are not very accurate. I would take my chances with a long pipe even without a torque wrench over an air wrench. A real powerful air wrench  can do tremendous damage in the blink of an eye.
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« Reply #24 on: February 28, 2009, 02:40:43 PM »

You guys seem to be missing something VERY important....and I think I have proof.  There seems to be a lot of concern about marking the gears with the impact wrench causing a lot of slap between the meshed teeth.  The gear teeth are NEVER supposed to have the torque of the tightening effort applied to them in the tightening process.  The yoke needs to be held/restrained/captured and the nut torqued against that restraint.  The "tool" looks like a piece of 1/2 inch plate with the dimension of the yoke cut out.  The plate slips over the yoke and the plate is then chained against rotation or is in contact with the floor.  All the torque applied to the nut is transferred to the restraining bar and the teeth never feel a thing.  I think that under normal ops the ring gear is bathed in oil and that oil film prevents metal to metal contact but at a start or in a stall situation the ring would be dry at the point of pinion contact so I guess there is room for intermittent contact but that would never be a hammer blow.

Admittedly, this is "car stuff" experience but I think it should apply.  I have never twisted a bus nut in anger so I don't know from experience there or from the Da Book.  Am I all wet?   Again?

John
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« Reply #25 on: February 28, 2009, 09:08:18 PM »

I also use the same method as John but have only done it on auto yoke nuts. I assume the same applies to heavy vehicles for the same reason, you really don't want to chip those gear teeth after all that hard work.
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« Reply #26 on: March 01, 2009, 02:41:50 AM »

Now about that pipe and torque wrench:  If you attach that T wrench to the nut and put a "cheater" bar on the torque wrench....the reading on the torque wrench is what the nut is torqued to.  Now, if you put a "breaker bar" on the nut and put a 10 foot pipe over the B bar, and attach the T wrench to the far end of the bar the torque read on the T wrench will be one tenth of the actual torque.  In neither case was the T wrench subjected to "over torque" abuse.  Correct me if I'm wrong. Please! Grin

John
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« Reply #27 on: March 01, 2009, 07:28:49 AM »

How would you attach a torque wrench to the end of a breaker bar or pipe?

JC
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« Reply #28 on: March 01, 2009, 09:53:33 AM »

weld on an old socket, etc.. to get a mounting point for the torque wrench.

Nothing sinister in it, twisting force is twisting force, no matter by air gun or using a pipe to increase the leverage by hand.

How do you know what torque the air gun is putting out, on this pull?

What sized airline, what restrictive fittings, what size tank is allowing what pressure drop, when was it last calibrated?  Manufacturers ratings don't mean squat, a recent calibration on the end of that air supply would be more comforting.

A 1 inch gun needs a big hose and big fittings, a maximum length of run,  all the way from the tank to the gun, with a big tank and a healthy compressor to achieve the advertised results. Otherwise, you'll get much the same or worse than a smaller gun on the same small hose.

For the inspired, someone step in with the hose recommendations?

Big boy toys, need big boy tools.

happy coaching!
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« Reply #29 on: March 01, 2009, 10:25:39 AM »

The hose varries. My IR 281-S6 (Japan) works just as well with a 3/8 hose as a 1/2 hose. It is very well engineered and uses less than half the air it takes to turn a China gun or CP, so it depends on the quality of the tool.

Trucks in local service that do alot of backing up have a habit of rolling the pinion nut off. After the first time of pulling the compensator, to get at it, I spot weld the pinion nut so I don't have to keep doing it over.

Gears out of the vehicle get a 2/4 stuck in the ring and pinion to tighten the nut or they start spinning pretty fast and they are real heavy and want to move around on the floor. Good for a laugh but kind of dangerous!

Gears back in the rig don't leave much choice but to put the axels in and just get it done. Spot welding the nut will make sure it stays where you want it forever and if you do that you don't have to be as critical with the torque because it ain't commin loose again. The down side is it ain't commin loose again either.

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Gold is the money of Kings, Silver is the money of Gentlemen, Barter is the money of Peasants, Debt is the money of Slaves.

$1M in $1000 bills = 8 inches high.
$1B in $1000 bills = 800 feet high.
$1T in $1000 bills = 142 miles high
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« Reply #30 on: March 01, 2009, 12:57:47 PM »

Everything The Warrior said. I have a 1 inch that needs the 1/2 inch hose and the shop has one from Harbor Freight that says  3/8 inch is sufficient.  I would give that Bad Boy all the air I could.

John
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« Reply #31 on: March 01, 2009, 04:07:45 PM »

John Ed is absolutely correct, the whole point of my posts. Why try to grunt out 600lb-ft when you can do 60?

However, the torque on the breaker bar will still be 600 so that is a really good argument for a 1" breaker.

JS,

I would weld a nut to the end of the pipe and use a socket on the TW.
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« Reply #32 on: March 01, 2009, 04:19:50 PM »

Funny, when I changed the rear axle on my Crown after driving it for 25000 miles (in order to install a newer axle that would be compatible with the Telma retarder I was about to install), I removed that nut with my fingers!! Definitely not 1000 ft lbs or even a few inch pounds!!!
Amazing it kept going without issue!!
Well.....
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« Reply #33 on: March 01, 2009, 04:40:37 PM »

The failures I have experienced have been that the yoke gets all the splines reamed out.  I am told this takes a long time but is inevitable if the nut doesn't eliminate relative movement.  The bright side is they saw the failure coming and made the yoke out of soft iron and it reams out easily and never touches the hardened splined shaft.  Still leaves you stuck though.

This was fun!

John
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« Reply #34 on: March 02, 2009, 04:56:48 PM »

Since this nut determines the pinion bearing preset it is amazing that a loose one wouldn't wipe out both pinion and ring gear teeth?

I have a Jeep with rounded off pinion and ring gear teeth from just that very thing. However, improper gear lash will do the same thing so it could be either.
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« Reply #35 on: March 02, 2009, 05:13:50 PM »

Gus, if JC's pinion is like an Eagle with the Rockwell it is a saddle mounted pinion the nut has nothing to do with preset it all done with the flange and shims.On Eagles and MCI 5's we don't have a yoke only a gear with a nut that we tighten with a impact gun works for us and I bet a buck he has a saddle mount pinion     good luck
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« Reply #36 on: March 04, 2009, 01:20:06 PM »

Update: I just installed the yoke nut this morning on the diff., and the output shaft nut on the trans. (replaced the oil seal there too). I applied red thread locker, then put them on with the impact wrench. By the way, there is no "gear slapping" while hammering away. I held the yoke while pulling the trigger, and the gears in the diff. or the trans. don't even touch each other. I finished with a breaker bar that I pulled with a come-along attached to a beam near the air bags. That was a lot easier than I feared! I indexed the nut relative to the yoke with a Dremel cutting wheel, so I can visually check once in a while that the nut hasn't moved. Meanwhile, I am putsing along at my engine overhaul. It all takes time, because I have other things in my life, like 2 teen-aged sons, my wife that cannot drive since she had a seizure at Christmas, helping with her Paint Horse operation, overseing a business, etc, etc... But I'll get it back together by Spring. I need the bus to take my sons to their dirt bike races. And I'd like to make it to Bus'nUSA in Rickreal, OR again this year.

Thanks again guys,

JC
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