1990 K3500 Dually Front Rotor/brakes replacement questions

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Afternoon,

I recently ordered front brake pads and rotors from NAPA. Realized after purchase it appears I have to separate the from hub bearing to replace the rotors.

Do I need to go ahead and do the hub bearing assy while I am in there? If so what do I need to look out for and ensure I am ready for tools and such before breaking into the job. Never had to remove and press studs before.

ABS sensors as well? Truck has had the upper and lower ball joints and control arm bushings replaced in 2020.

Thanks
 

Schurkey

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I have not done this job.

My K2500 7.4L has the same goofy, hard-to-service front rotor system as the 3500s. The service manual is NOT much help in terms of replacing the rotor on the hub assembly.

Looked it up in my '97 service manual.
Remove tire/wheel.
Remove caliper.
Remove center nut on CV axle
Remove bolts (4) on back side of steering knuckle that retain hub/bearing assembly.
Use BIGASS Puller to rip hub/bearing out of steering knuckle, taking the rotor assembly with it. Apparently, the puller is pushing on the CV axle, which doesn't make sense to me. But that's what my manual shows. There's also not word one about the ABS wheel speed sensor.

Replacing the rotor itself is somehow not specified--but I'm sure it involves knocking all the lug-studs out. No promises on them being re-usable afterwards. I would want to know that there were 8 lug studs available locally for each replacement rotor, in case I needed them.

Truthfully--I think the service manual is missing important info on this procedure.

Fortunately, my rotors seem to be in reasonable condition. Pulled the LF caliper apart today, RF comes apart tomorrow to clean out the sludge inside and to assure the caliper floats on the rubber mounts.
 

Supercharged111

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There are no front ABS wheel speed sensors a on a 90 so no need to scratch your head over than one. They're RWAL only and that sucks hard even when it works properly. I deleted mine on my 88. It got really invasive on a muddy ass road one day so it went in the dumpster.
 

mr_josh

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Did this recently on my 8-lug K2500 and Schurkey has it pretty much right.

What you’re doing with that puller is disengaging the CV axle from the hub so you don’t end up pulling apart a CV joint while pulling the hub assembly. Mine had very little rust so a few taps with a mallet cushioned with a piece of wood was good enough to disengage the axle end from the hub (I don’t think you’re really supposed to hammer the axle end so I tried to be gentle).

It’s a PITA but it’s at least not a frequent service item for most folks. I used NAPA hub assemblies and they came with new lug studs. Get new CV axle nuts while you’re at the parts store. There are seals at the back of the knuckle where the CV axle passes through and you could replace those if you are so ambitious but mine were at least intact so I left them alone.

It’s pretty straightforward once you get in there. Good luck.
 

Schurkey

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OK. Thanks for that.

I thought the puller was to yank the hub out of the steering knuckle. Apparently, it's to push the CV stub shaft out of the hub. I'd have never guessed that.

The '97 service manual is so fooked-up on this that they don't even acknowledge that the 8-lug 2500s use this system--they say its for the 3500, and that the 2500 uses the composite rotor that slides over the lug studs on the hub.

So the NAPA hubs come with lug studs, but the NAPA rotors don't. I suppose that the lug studs are available, though.
 

454cid

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Ok, not in order, by any means.

I've don't this twice, myself. The first time, I bought Timkin hubs which had new studs. The second time, I only replaced one side, and didn't get studs. I support the assembly on blocks and pound out the studs. A lugnut screwed onto the end takes the beating and prevents the stud from being mushroomed.

Putting the studs back in: Once I asked a shop to do it, and it was done with an air hammer. When I did it myself, I used a lug nut and a couple of greased washers to pull the stud through after getting it started from the back with a hammer..... with everything supported to the bearing wasn't getting beat up. A couple of studs didn't really get seated until the wheel was back on.

If re-using parts make sure all rust and dirt is gone. I used a wire cup on a angle grinder. I still had to re-do one side as runout, as checked with a dial gauge, was out of spec. I apply antiseize to all mating parts so they aren't stuck the next time.

Removing the hub from the knuckle: The last time, I had one side I had to beat out, and the other basically fell out. I think I pounded on the loose bolts from the back. I've heard that the Dodge guys will use and extention wedged in between the hub and something solid and push them out by turning the wheel. I'm not sure if that would work on our trucks. Those 4 bolts are availble from GM and Dorman.... they're not that expensive. Replace them if they are questionable at all. Make sure you can get the socket fully seated before applying torque while trying to remove them.... maybe tap the socket on with a brass hammer after scrapping out any crud from around the bolt heads.

I have not used any kind of puller, just hammers applied with caution.

I use anti-seize on all threads after cleaning them with a wire wheel.

I test lugs being re-used with a known good lugnut, and then tested each lugnut, making sure I had 16 of each..... I had extras of both saved.

My 99 manual doesn't really describe this eithier. It basically says "remove rotor", as if it were a 1/2 ton with slip on rotors. The drawings are horrible and the manual edited poorly.

I have re-used spindle nuts, and not had a problem. The first time, I think I used anti-seize on them so they wouln't get so stuck, and also to lower the torque requirement, as the torque spec is quite high.... higher than any torque wrench I have available. This last time, I may have used Loctite, but I don't recall for sure. To remove the nuts initially, I used heat, penetrating oil, and a breaker bar. The last time, I had to use an impact.
 

454cid

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With your miserable ass experience of cracking rotted ass parts open because salt and MI? I want very explicit adjectives/adverbs and blame placed for incompetency on design good sir.

It wasn't so bad the last time. Back in 2007, I had no clue what I was doing. I do not know why GM designed the 8-lug trucks this way. Maybe it has some hidden engineering benefit that we don't see? I always wanted to do a GMT-800 knuckle swap, and rotor replacement was a big reason why, besides the better dual piston calipers and better stopping.
 

Carlaisle

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One addition I would make regards the axle nut. I think it's a 36mm, but don't quote me on that. Buy/rent several sizes in advance and check their fit. The slop is likely from the chinesium socket manufacturers rather than GM's supplier, but the fit is definitely inconsistent. I don't know if the torque spec changed over the years. The later models are supposed to be torqued to 175 ft lbs. When I attempted to take it apart the first time my 1/2" breaker bar flexed so much I thought it was actually going to break. Ended up using a 3/4" breaker bar and 4' cheater to get it loose.
 
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