8 3/4 center sections

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mopar3401987

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So I two 8 3/4 center section one is a 741 the other a 742 I noticed when I turned both of them one is alot easier to turn then the other . I put them both up to dial indicator and noticed that the lash is set correctly on the both of them . why would one have less resistance to turn than the other ?
 

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mopar3401987 said:
So I two 8 3/4 center section one is a 741 the other a 742 I noticed when I turned both of them one is alot easier to turn then the other . I put them both up to dial indicator and noticed that the lash is set correctly on the both of them . why would one have less resistance to turn than the other ?
Click to expand...

depends on the mileage/wear on the pinion bearings and the rust on the gear teeth doesn't help.
 
No rust on the teeth that I can see of anyone know the torque spec for the nut that holds the yoke on ?
 
I am trying to figure out why my 741 case is easier to spin /turn then my 742 case I checked the lash which is fine according to the hot rod magazine article I was reading. I stuck a gauge to the back of the nut that holds the yoke down and spin it .the 741 case was 14 inch pounds and the 742 was 23 inch pounds is this normal ? I don't see any thing in the article About preload
 
One is heftier than the other. And with the 742 having higher ratio it just makes it compounded.
 
mopar3401987 said:
I am trying to figure out why my 741 case is easier to spin /turn then my 742 case I checked the lash which is fine according to the hot rod magazine article I was reading. I stuck a gauge to the back of the nut that holds the yoke down and spin it .the 741 case was 14 inch pounds and the 742 was 23 inch pounds is this normal ? I don't see any thing in the article About preload
Click to expand...

There is your difference, just like RRR said, there is more preload on one than the other, making it a bit stiffer to turn. There is preload set on any bearing that you install, rear ends, front hubs/disks etc.

I think on a 489 case it's 19 inch pounds, so they might vary, I don't know.
 
Rear_Axles_11.jpg



It appears I was a tad off on my number, I was relying on memory.

It looks like, 741-25, 742 - 35 and 489 - 35. All in inch lbs.

That is for NEW bearings.

I would not be concerned with what you have right now, as they are used units. Unless they have been completely rebuilt.
 
Yes there used I have no idea how many miles are on them but I thank you for the information looks like these Will work out good for my car thanks for the info guys !
 
and carrier bearing preload, which set correctly will add about 9 in/lbs to required turning torque with new bearings, about 4.5 when well broken in. 741 and 742 pinion nut torque=240 ft/lbs. Turning a used 741 or 742 with correct pinion bearing and carrier bearing preload and a pinion seal and good bearings = about 17 in/lbs . Gear ratio turning it on the bench is not relevant-instructions on setting preload never mention ratios
 
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