Stock Ubolt Replacement

[johnckhall]

Probably going to replace my stock leafspring / axle ubolts tomorrow. Am I missing anything?

Floor jack under the rear differential + jack stand on the axle side I'm working on.

* Or should I jack up and put a jack stand on both sides of the axle and have both tires off the ground? Working on one side at a time.

Remove tire, obviously
Cut old rusted U-bolts off. Be careful with flying ends. Clean up old rust
I'm replacing ubolts, plate, and leaf spring spacer
Tighten nuts to spec diagonally onto plate. Once on the ground?
Check torque at 50, 100, and 500 miles

 

[tpass]

I would have jack stands under the frame as well as under the axle, yes to having the wheels off the ground, you'll need to get them out of your way anyway.

One side at a time is good too, keeps the axle in position and gives you the option to do the other side on a different day. The bolts will sound like a gunshot going off when you cut them, FYI

 

[1997]

I'm replacing ubolts, plate, and leaf spring spacer

where did you get the new "stuff", LMC? thx.

 

[Schurkey]

Are the "new" U-bolts the same diameter as the originals? If they sold you larger-diameter U-bolts, the torque may be different.

When I install stock-diameter U-bolts, I use anti-seize on the threads, and lower the torque spec by ~20% to account for the reduced thread friction from the lubed threads.

 

[johnckhall]

where did you get the new "stuff", LMC? thx.

I got the Ubolts (9/16 Husky) and Leaf Spring Spacer from RockAuto. I ordered the plate from one of the GM replacement parts websites that I googled. I went with OE on the plate

 

[johnckhall]

Are the "new" U-bolts the same diameter as the originals? If they sold you larger-diameter U-bolts, the torque may be different.

When I install stock-diameter U-bolts, I use anti-seize on the threads, and lower the torque spec by ~20% to account for the reduced thread friction from the lubed threads.

The 9/16 Husky U Bolts from Rockauto came with recommended torque. 90 ft/lbs recommended.

 

[Supercharged111]

The 9/16 Husky U Bolts from Rockauto came with recommended torque. 90 ft/lbs recommended.

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90 won't cut it with that fat of a bolt. I don't have a number for you. I used 9/16" on my dually and used German torque: gutentight.

 

[Nad_Yvalhosert]

90 won't cut it with that fat of a bolt.

I agree. I work in a suspension shop. We tighten them till the socket stops turning. Full max on my 1/2" gun is 1150 reverse, 900 forward. I suppose that means the u-bolts are somewhere around 800+ lb-ft.

And we don't get comebacks from loose axles.

 

[Schurkey]

What does it take to crush/distort the axle tube?

800 ft/lbs on a 9/16 U-bolt? Doesn't sound reasonable.

(Advertised torque ratings of impact wrenches seem to have only a fleeting relationship to reality.)

There's also the matter of fine-thread vs. coarse thread. The original U-bolts on my K1500 had coarse threads, the replacement U-bolts had fine threads. That's gonna screw with the torque recommendations.

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[evilunclegrimace]

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90 won't cut it with that fat of a bolt. I don't have a number for you. I used 9/16" on my dually and used German torque: gutentight.

The factory torque spec is 81 lb. ft. for single rear wheel trucks and 109 lb. ft. for dual rear wheel trucks.