M8 Bolt disaster, some help and advice needed inside...

[Grug556]

Never start a fastener with a wrench. Impact off, never impact ON. Words to live by.

Either you have exceptionally bad luck or those M8 bolts were ugga-dugga'd when reinstalled.

That said, the suggestion of getting a nut welded is a good one - beyond giving you some purchase on the remaining stud, the heat that a welder will send through that fastener will definitely help break the bond.

Hope you are able to get it licked!

ha we think alike..I always use impact for off.

 

[Grug556]

Unless you get the extractor and drill bit pieces out, it won't matter where or on what type of drill you're drilling. Those two things are as hard, or harder than the drill you're using. You have got to chip them out somehow, or like it's been said, go with the weld a nut on technique. I know it sucks, because it's not an easy place to work, but you might want to try that before removing that cross member. If you HAVE to you can try solid carbide drills (available at McMaster Carr) to remove the broken pieces. However, be advised, they are as brittle as glass, and if you break one of them off, it will need to come out with force, or by burning it out on a tap extractor.

yeah this is the issue here, cant drill metal harder than the cobalt bit. trying to find a welder now

 

[Bobby12many]

You could always look at finding a used crossmember and prepping/swapping it in vs spending a few dozen hours on extraction. Cant be a hugely in-demand part and lord knows there are enough 5th gens out there being parted/scrapped.

If you are pulling it anyway, might be better to start fresh(er) and just chase/prep all threads of the replacement?

It would appear that this is the bare transmission crossmember - under $100....
TRANSMISSION Crossmember TOYOTA 4RUNNER 06 | eBay

clean threads in your area of interest....


I may be off on compatibility, but wanted to chime in in case it set off any lightbulbs

Cheers

 

[Grug556]

You could always look at finding a used crossmember and prepping/swapping it in vs spending a few dozen hours on extraction. Cant be a hugely in-demand part and lord knows there are enough 5th gens out there being parted/scrapped.

If you are pulling it anyway, might be better to start fresh(er) and just chase/prep all threads of the replacement?

It would appear that this is the bare transmission crossmember - under $100....
TRANSMISSION Crossmember TOYOTA 4RUNNER 06 | eBay

clean threads in your area of interest....


I may be off on compatibility, but wanted to chime in in case it set off any lightbulbs

Cheers

Thanks yeah thats the part. I have it going into a machine shop on Monday to drill through the parts. We will see how it goes. I have never seen such poor quality fasteners ever. I had a 30 year old VW rusted to shit with bolts that werent as bad as the 4 runner.

What grade of bolt does Toyota use as OEM?

 

[Bmnorm2]

Thanks yeah thats the part. I have it going into a machine shop on Monday to drill through the parts. We will see how it goes. I have never seen such poor quality fasteners ever. I had a 30 year old VW rusted to shit with bolts that werent as bad as the 4 runner.

What grade of bolt does Toyota use as OEM?

There is such a thing as too high of a grade for the application. For example, using a 12.9 on a soft (plastic) joint. The class is so high you can't get the adequate % of yield without embedding into the material.

Depending on application there is a target range of % material yield stress you want to hit with your torque, while also preventing embedding into the material under the head, and having adequate thread engagement. Lastly, a good design will fail the bolt, not the internal mating threads.

Your issue is likely more related to a corroded bolt that you impacted off. The corrosion is a matter of the type/quality of anti-corrosive coating/plating/diffusion.

 

[Grug556]

There is such a thing as too high of a grade for the application. For example, using a 12.9 on a soft (plastic) joint. The class is so high you can't get the adequate % of yield without embedding into the material.

Depending on application there is a target range of % material yield stress you want to hit with your torque, while also preventing embedding into the material under the head, and having adequate thread engagement. Lastly, a good design will fail the bolt, not the internal mating threads.

Your issue is likely more related to a corroded bolt that you impacted off. The corrosion is a matter of the type/quality of anti-corrosive coating/plating/diffusion.

yeah thats what I was wondering, I think the bolts there used have no anti corrosive properties. The frame beside it and other parts underneath it have small to limited corrosion, where as the bolts are almost obliterated and pitted with heavy corrosion.

For replacement bolts I got 10.9 with anti corrosive coating. Some of the OEM bolts have rusted so bad their heads are not fully visible with sides on them, all melted looking. I keep this thing in the garage and hardly drive it anymore so I am puzzled they are this bad this soon. Its a low mileage truck. I have a new 2021 limited i use the most and the 2016 limited has maybe 35000 miles on it. Not much for such rust.

 

[Bmnorm2]

yeah thats what I was wondering, I think the bolts there used have no anti corrosive properties. The frame beside it and other parts underneath it have small to limited corrosion, where as the bolts are almost obliterated and pitted with heavy corrosion.

For replacement bolts I got 10.9 with anti corrosive coating. Some of the OEM bolts have rusted so bad their heads are not fully visible with sides on them, all melted looking. I keep this thing in the garage and hardly drive it anymore so I am puzzled they are this bad this soon. Its a low mileage truck. I have a new 2021 limited i use the most and the 2016 limited has maybe 35000 miles on it. Not much for such rust.

A lot of OEMs use an option Magni Coat on their bolts. I see Toyota has a spec associated with Magni 565.

https://magnicoatings.com/wp-content/uploads/2016/10/Magni-565-Product-Data-Sheet.pdf

It’s good stuff, but honestly 1000 Hrs of ASTM B117 Salt Spray with white rust but no red rust doesn’t translate to that long in corrosive environments (Snow states with salt roads or coastal with salt air).

10.9 for those should be just fine.

 

[T4R_Canuck]

Fellow Canadian here. I bought my 14' used in stock form with 150k. I slowly got to work replacing skids and such with something useful instead of the stock stuff and found lots of over torqued, rounded off and rusted bolts. I removed all the stock stuff, ran a tap into all of the threads and reinstalled with grade 10.9 bolts and a heavy dose of never seize. I've had the rig for nearly 3 years and do all my own maintenance and have yet to have a problem removing a bolt, which has been nice.

I had a similar situation removing one of the stock bolts when I bought mine. Looked like Mr. Dealer (vehicle was dealer serviced its entire life before I bought it) had over tightened every skid plate bolt and nearly twisted the heads off of a couple of them. I used Kroil (penetrating fluid) and gave them several doses a day for a couple of days, then gave them a couple good hits with a hammer before clamping a pair of vice grips to the bolts and wiggling them in/out a mm at a time while applying heat until they finally broke free and I could take them out fully.

 

[Grug556]

A lot of OEMs use an option Magni Coat on their bolts. I see Toyota has a spec associated with Magni 565.

https://magnicoatings.com/wp-content/uploads/2016/10/Magni-565-Product-Data-Sheet.pdf

It’s good stuff, but honestly 1000 Hrs of ASTM B117 Salt Spray with white rust but no red rust doesn’t translate to that long in corrosive environments (Snow states with salt roads or coastal with salt air).

10.9 for those should be just fine.

Interesting thanks for posting that. Zinc rich at 1000 of B117 doesnt really show anything of value. Typical bullshit spec. Of better interest is their cyclic testing, but its only a 120 cycles and doesnt define cycle type. G85 Annex 5 maybe or similar might be better test, but its very aggressive and lots of companies wont run such stuff knowing they will fail. when they started to remove chrome from both conversion coating and final coating on fastener things went downhill quality wise.