Knuckle Thread Repair (Caliper)

[PatrickM]

I've been doing a full front axle service today and noticed a little problem while cleaning my knuckles. The lower caliper hole was heli-coiled and was helicoil subsequently damaged when I removed the bolt. I didnt notice while disassembling. I only noticed after cleaning the grime off of the knuckle.

I did find it strange that the lower bolt was 18mm hex and the top, a stock bolt, was 17mm. Additionally, the stock hole's threads are buggered pretty good. Someone really got sloppy on this knuckle.

The helicoil repair is M12x1.75
Stock is M12x1.25

Both of these holes need repair. I think I could get away with a tap through the non-repaired hole but the bottom hole needs a new repair.

I dont have much experience with helicoils, but could I replace the present, failed repair (M12x1.75) with a M12x1.25? Say I bought a M12x1.25 helicoil kit, could I repair both holes that way or is the already present helicoil hole going to require an even larger hole? Any input is greatly appreciated as I need to get this fixed this week.

The bolt on the left is from the botched helicoil, and the right is an original bolt that someone seriously galled.

Helicoil coming out easy after cleaning the knuckle (notice missing threads on bolt).

 

[dirtEJohnson]

The question of what could be repaired is secondary to what should be repaired. The brakes are merely adequate on these heavy machines even when in perfect shape. What seems like a solid repair may prove otherwise when it is needed most.
IIRC,the knuckle is common to any 4wd Toyota of similar vintage and relatively cheap to replace.

 

[Output Shaft]

^^
That
Don't risk your life or that of your passengers to save what amounts to the cost of 2 tanks of gas. Replace the knuckle with a good used one.

 

[PatrickM]

Yeah, you both make good points. I should really just replace it rather than repairing it a second time. Thanks for the input

 

[Dynosoar]

If you do decide to make the repair, do it correctly. Do NOT use a helicoil. Helicoils are great for some applications, this is not one of them. You can and should use a Timesert. There is a ton of info on the web about them, such as cost, availability, how to, etc. If it was me I would look for a good used knuckle, but I would feel 100% safe with a timesert repaired knuckle too.

Dyno

 

[PatrickM]

Thanks Dyno. My immediate thought was to use a Timesert having had great success with them in the past.

I think I'll be looking for a replacement though... Cruiserparts has one for 40, SOR has one for 180.... Not sure what the catch is there, but I need to make a choice.

 

[Dynosoar]

Cruiserparts = more rusty and crusty (roll the dice) SOR=high cost+high shipping but little rust and crust

If you have worked with Timeserts before ,and you are comfortable working with them, then think about going that way.

Dyno

 

[Wile E Coyote]

I'd lean towards repairing the current threads to avoid the need to reset the bearing preload that comes with a replacement knuckle.

 

[Spike Strip]

FWIW, though I agree a Time-Sert is a better solution, many people have used Helicoil without issue. Red Loctite on the insert helps. Also, you'll find the Time-Sert is very expensive, unless you have access to an install kit and just buy an insert, a replacement knuckle will probably be cheaper.

Another solution is to drill out and tap to a 1/2" fine and enlarge the caliper hole.

 

[PatrickM]

Thanks for the very helpful replies... I'd really like to be able re-use this knuckle and repair it with a Time-Sert (kits are around $100) but ultimately it's not a good idea. Had this been a first time thread repair, I wouldn't hesitate to use a Time-Sert. However, this hole would need to be opened up even more than it is now (its close to 13mm in diameter now with the Helicoil repair). The stress concentrations could be a source of potential failure on the relatively small tang that this hole is machined through.

I ended up finding a used one that I will replace this knuckle housing with. Unfortunately, I run the risk of misalignment because I really need to get this back together and don't have a source for the alignment tool. I'm hoping that the Marlin inner axle seals are forgiving enough for a couple thousandths of non-concentricity.

 

[cruisermatt]

If you're not changing your tie-rods you aren't effecting alignment. If you are use string and measuring stick as outlined in the FAQs.

 

[FJ60Seth]

You can center the housing by trial and error. The shims center the axle vertically. If not centered correctly, you won't be able to even tighten the top & bottom bolts, or if you can, the knuckle is going to be too tight or loose when turned, hence the bearing preload test.

1. Put everything back together and try to torque the top and bottom bolts to spec.

2. If the bolts seem like they won't tighten, the alignment is way off. Don't force it. Stop and try a different combination of shims. As the axle gets closer to centered, the bolts will all tighten.

3. Once you can tighten the bolts to spec, check the preload. If it's out spec (too loose or tight), try a different combination of shims.

Repeat until preload is good.

 

[Skniper]

If you're not changing your tie-rods you aren't effecting alignment. If you are use string and measuring stick as outlined in the FAQs.

Not talking about that alignment. He's referring to the alignment of the axle and birf as it relates to centering it in the knuckle housing, axle tube, and spindle. This is done with the knuckle cap shims.

 

[cruisermatt]

In that case you should have a rebuild kit that will include them, I wouldn't be opening the knuckle without one on hand.

 

[PatrickM]

I have plenty of shims of various thicknesses. I am referring to the procedure outlined on pages FA-23 and FA-24 of the FSM. Specifically referring to the SST used in setting proper preload and alignment of when replacing a knuckle housing. But it looks like I can do it without the tool as Seth mentioned above

 

[PatrickM]

This debacle has put me way behind schedule but I was able to finish the one side after refreshing a used knuckle I received. At this risk of being flamed, can anyone think of reason why it would be a bad idea to temporarily postpone doing the other side knuckle rebuild? I need to have this truck back together for a trip next week and I can't afford any more surprises right now (like damaged threads). I can't think of any reason that it would make it a bad idea. I'm still going to replace the wheel bearings on the other side. I'll just keep the spindle/axle/knuckle housing intact until I get back.

Some pics of the refreshed, used knuckle housing I bought to replace the damaged one. Cleaned, painted, threads chased, new studs installed.

As received. Surprised it didn't leak through the package

 

[FJ60Seth]

Nice job rehabbing that nasty looking knuckle. I don't see a problem with a break between sides.

 

[Skniper]

Did a business send you that nasty sh*t? --> Wrong! Nice cleanup on your part.

No different than a trail repair and leaving the other side, IMO.

 

[Dynosoar]

If I got that in the mail I would Freak! Like they could not have hit it with a pressure washer or let it soak in a solvent tanks/ parts washer.

must be cruiserparts


Dyno

 

[PatrickM]

I was going to say that the business name rhymes with Looser Farts... But yeah. I was pretty annoyed with the lack of cleanliness and the fact that they state that "all used parts are in good working order". How would one be able to honestly assert that with so much grime on the part? I Also didn't get a good feeling when I was asked if I was looking for a front or rear knuckle housing. [emoji16]