Pinion drag or pinion preload
Thread Starter
2nd Gear
Joined: Nov 2015
Posts: 2
Likes: 0
From: Gilbert Arizona
Pinion drag or pinion preload
Perhaps someone could help me with this 87 coupe differential rebuild question. When you're setting up the pinion drag or pinion preload(87 coupe DANA 36) you use an inch/lb
torque wrench and it calls for I believe 15-35 inch/lbs. I don't understand where this friction comes from. I get basically zero as I spin the pinion with the torque wrench.
The only way I get an opposing force as I spin the pinion is to tighten the pinion nut with an excessive amount of torque and I don't think that's right for the pinion bearings.
Someone explain where the drag comes from?
torque wrench and it calls for I believe 15-35 inch/lbs. I don't understand where this friction comes from. I get basically zero as I spin the pinion with the torque wrench.
The only way I get an opposing force as I spin the pinion is to tighten the pinion nut with an excessive amount of torque and I don't think that's right for the pinion bearings.
Someone explain where the drag comes from?
Le Mans Master
Joined: Aug 2017
Posts: 6,944
Likes: 1,490
From: New Jersey
It should be preload on the bearings. I'm not sure with how the Dana on these works but there is usually shims or a crush sleeve to allow the tightened nut to press against... the nut being very tight sounds correct from what I remember on the 10 bolt I did. Now this is an entirely different rear end so that may or may not be correct at all... but the rolling resistance should be based off of the preload on the bearings... that is pretty much a constant.
So basically you are compressing the bearings x amount against their races. That pressure is what sets the preload.
So basically you are compressing the bearings x amount against their races. That pressure is what sets the preload.
Last edited by 84 4+3; Mar 24, 2021 at 07:20 PM.
Team Owner
Joined: Aug 2004
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From: Park City Utah
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Last edited by Tom400CFI; Mar 24, 2021 at 07:36 PM.
Melting Slicks
Joined: Jan 2014
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From: Lunenburg MA
Melting Slicks
Joined: Jan 2014
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From: Lunenburg MA
Burning Brakes
Joined: Aug 2006
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From: Seattle WA
Keep in mind that the bearing pre-load is usually a different spec for new bearings vs re-installing the original bearings (i.e. don't preload them twice). Not 100% sure that's the case for the D44 as I haven't done one of those, but in the BMW's I've done, the re-install pre-load is always much less than what you'd dial in for a new bearing.
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Racer
Joined: Feb 2005
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From: Quincy,Illinois
If you are reusing the factory Dana gears, they use shims to set the preload. If you are using an aftermarket gear like a Yukon, they use a crush sleeve. If you installed new bearings with the same shim pack there can be a slight difference in the bearings so you will need to adjust the shim pack. To increase preload, decrease the thickness of the shims. If you have noticeable end play in the pinion, check it with a dial indicator and decrease the shim pack by that amount to start. Then decrease shim pack by .001-.002 at a time until the desired preload torque is achieved. Use the old pinion nut to set preload then use new nut on final assembly.
Last edited by IBVETN2; Mar 27, 2021 at 12:33 PM.