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Author Topic: Differencial yoke nut torque?  (Read 4591 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
Invermere, BC
1977 MC5C, 6V92/HT740
luvrbus
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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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Utahclaimjumper
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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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Utahclaimjumper 
 EX 4106 (presently SOB)
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lostagain
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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
Invermere, BC
1977 MC5C, 6V92/HT740
gmbusguy1
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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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Utahclaimjumper
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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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Utahclaimjumper 
 EX 4106 (presently SOB)
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 72 VW Baja towed
Sam 4106
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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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gmbusguy1
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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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JC
Invermere, BC
1977 MC5C, 6V92/HT740
luvrbus
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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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NJT 5573
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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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Sam 4106
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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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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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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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junkman42
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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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Utahclaimjumper
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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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Utahclaimjumper 
 EX 4106 (presently SOB)
Cedar City, Ut.
 72 VW Baja towed
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