The Ford Barn

Tom Elliott · 03-04-2015, 09:03 PM

Just wondering- If you have a differential bearing preload set at 20 in. lbs. and a pinion bearing preload at 20 in. lbs. what would the driveshaft read when turning it with a in. lb. torque wrench? Not factoring in ring and pinion gear contact and the driveshaft roller bearing. Don't know what kind of formula to use to figure that out. Thanks, Tom

J Franklin · 03-04-2015, 09:13 PM

Why?

Tom Wesenberg · 03-04-2015, 09:23 PM

With a 3.78 ratio you would divide the differential preload by 3.78 and add that to the pinion preload.
I set them up by feel and they work fine.

Tom Elliott · 03-04-2015, 09:40 PM

Just curious how much torque it would take to turn the rearend gears with the driveshaft with all the bearing preloads.

Kevin in NJ · 03-04-2015, 10:24 PM

Not a good question.

Preloads are to ensure proper clearance as everything wears into each other so the loading gets reduced after some use. Then there is the question of what lubricant and what temperature. The oil will have a significant effect on the torque and oil curve can cover a lot of ground. 100 degree oil will be much thinner then 50 degree oil making for more torque need at lower temps.

So in the end, you do the pre-loads right individually and put it together and trust you did it right. Of course, you always have to spin the drive shaft and watch the axles move cause you just built and and you can.

J Franklin · 03-04-2015, 10:29 PM

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Kevin your answer was much better than what I was thinking, but knew there were other factors and If both were correct it would thus be correct.

03-04-2015, 09:03 PM	#1
Tom Elliott Senior Member Join Date: Oct 2014 Location: Peyton, Co. Posts: 100	Rearend bearing proload question. Just wondering- If you have a differential bearing preload set at 20 in. lbs. and a pinion bearing preload at 20 in. lbs. what would the driveshaft read when turning it with a in. lb. torque wrench? Not factoring in ring and pinion gear contact and the driveshaft roller bearing. Don't know what kind of formula to use to figure that out. Thanks, Tom

03-04-2015, 09:13 PM	#2
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,962	Re: Rearend bearing proload question. Why?

03-04-2015, 09:23 PM	#3
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Rearend bearing proload question. With a 3.78 ratio you would divide the differential preload by 3.78 and add that to the pinion preload. I set them up by feel and they work fine.

03-04-2015, 09:40 PM	#4
Tom Elliott Senior Member Join Date: Oct 2014 Location: Peyton, Co. Posts: 100	Re: Rearend bearing proload question. Just curious how much torque it would take to turn the rearend gears with the driveshaft with all the bearing preloads.

03-04-2015, 10:24 PM	#5
Kevin in NJ Senior Member Join Date: May 2010 Location: South East NJ Posts: 3,398	Re: Rearend bearing proload question. Not a good question. Preloads are to ensure proper clearance as everything wears into each other so the loading gets reduced after some use. Then there is the question of what lubricant and what temperature. The oil will have a significant effect on the torque and oil curve can cover a lot of ground. 100 degree oil will be much thinner then 50 degree oil making for more torque need at lower temps. So in the end, you do the pre-loads right individually and put it together and trust you did it right. Of course, you always have to spin the drive shaft and watch the axles move cause you just built and and you can.

03-04-2015, 10:29 PM	#6
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,962	Re: Rearend bearing proload question. Sponsored Links (Register now to hide all advertisements) Kevin your answer was much better than what I was thinking, but knew there were other factors and If both were correct it would thus be correct.