Author Topic: 4WD Front Wheel Bearing Pre-load?  (Read 1555 times)

Offline Jon87V20

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4WD Front Wheel Bearing Pre-load?
« on: July 14, 2018, 02:40:58 PM »
I'm replacing both front rotors, hub assemblies, calipers, and all wheel bearings on my '87 Suburban V20 today.

I'm trying to figure out what to do about the bearing pre-load. I'm getting some conflicting information when I'm looking around about this. I'm seeing videos where people are pre-loading the bearing to 50 ft-lbs., then backing it off an eighth of a turn, I'm also seeing in the Service Manual PDF that you should never pre-load the front bearings as it will cause premature failure.

When I took the driver's side apart yesterday, the outer spindle nut was basically finger tight, and the inner one didn't take much effort to get out either.

Any advice is much appreciated as I would really like to get this all back together today. Need the truck for work on Monday.

Thanks!
1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline VileZambonie

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #1 on: July 14, 2018, 04:53:05 PM »
Adjust the bearings by rotating the hub and tightening the inner adjusting nut to 50 ft. lbs., then loosening it and retightening to 35 ft. lbs. Next, back the nut off 3/ 8turn or less. Turn the nut to the nearest hole in the lockwasher. Install the outer locknut and torque to a minimum of 80 ft. lbs. (108 Nm) on 1980 models, 160-205 ft. lbs. (216-277 Nm) on 1981 and later 1/ 2and 3/ 4ton models, and 65 ft. lbs. (88 Nm) on 1 ton vehicles. There should be 0.001-0.010 in. bearing end-play. This can be measured with a dial indicator.
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Offline Jon87V20

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #2 on: July 15, 2018, 01:47:17 AM »
Ok. Thanks, Vile. By the way, I have to ask, what's going on in your profile picture there? Some kind of action figure or something?
1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline VileZambonie

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #3 on: July 15, 2018, 06:25:14 AM »
It's the toy that became Omega Supreme (pre-transformers) and I got it for my birthday when I was a kid. My buddy came over to play and broke it, of course I got mad at him and he would always bring it up every time I saw him. He committed suicide unfortunately so I changed the picture to commemorate our friendship.
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Offline Jon87V20

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #4 on: July 16, 2018, 12:49:06 AM »
Vile, sorry to hear about your loss. Pretty awesome robot. Thanks again for the help.
1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline VileZambonie

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #5 on: July 16, 2018, 05:26:33 AM »
Thanks - Good luck
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Offline JohnnyPopper

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #6 on: December 25, 2018, 06:03:18 PM »
VZ, thanks for sharing the backdrop of your avatar. I've tried to enlarge it, gave up thinking it was a pic of a motor... Sorry for your loss too.

I have the same 4X setup and need clarity on your instructions to 'back off 3/8 of a turn', do you mean 135 degrees?

Thanks!
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #7 on: December 26, 2018, 07:01:36 AM »
Yeah I'm about due to update the Avatar...

Just turn it back less than a 1/2 turn and then retighten to the next locking position.
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Offline 75gmck25

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #8 on: December 26, 2018, 07:25:34 AM »
The procedure Vilezambonie described is just about word-for-word from the repair manual.

- The 50 ft lb initial tightening sets the bearings into the races.  You will feel it pulling the hub in tightly and squishing out the grease.
- Then you loosen the nut and tighten it again to 35 lbs while rotating the hub.  This is really the part that puts a preload on the bearing.
- Then you back it off just enough to get the locking ring/washer to match up with one of the holes.  The locking washer is keyed, so it only goes on in one position.  That is why the washer and nut (pin and holes) might not line up at first. The book says you can back off no more than 3/8ths turn, but I've never had to back it off that far.
- Now you put on the final lock nut and tighten to 80 ft lbs (my '75 book says 50 ft lbs minimum), which keeps it all in place.

Bruce

Offline JohnnyPopper

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #9 on: January 02, 2019, 12:59:37 PM »
Thanks guys, I did the math and 3/8 is 130 degrees, sound like a lot, will play with it.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline MIKE S

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #10 on: January 02, 2019, 02:10:47 PM »
When adjusting the bearings, keep in mind if you have auto locking hubs they are engaged on the wings of the locking washer. That being said if they are not torqued to a minimum of 160 ft. lbs. the action of the auto hubs will work on the washer and tear up the spindle keyway and threads along with unscrewing the nut that will lead to catastrophic failure. 

Offline JohnnyPopper

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Re: 4WD Front Wheel Bearing Pre-load?
« Reply #11 on: January 03, 2019, 04:57:18 PM »
Thanks Mike, she's too old for that type of thomfoolery, 1978
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction