Stripped threads on rear shock lower mount!

[klk87]

While installing some new shocks I stripped the threads inside the bottom mount on the driver side. :bash:

It's pretty bad, the bolt barely catches any threads I can almost pull it in and out without much trouble.

I was thinking of 3 ways to proceed:

1. Retap the hole with a larger thread (maybe 1/2" since current thread is M12x1.25)
2. Drill further into the mount and tap the new drilled part with the same M12 thread and try to use a longer bolt which will hold on these new threads.
3. Drill completely through to the other side of the mount and secure with a long bolt and nut.

What do you all think?

 

[JAXJeremy]

Bummer..I'd retap to a larger thread..you could always use helicoils but I'm not sure I'd want to rely on those on a shock mount.

 

[QwikKotaTx]

Bummer..I'd retap to a larger thread..you could always use helicoils but I'm not sure I'd want to rely on those on a shock mount.

Keenserts are much better as they use a thick wall and have 2 to 4 keys that you hammer into the base metal to prevent counter-rotation but you need a lot of access room to drill and tap and typically the outer thread is 2 sizes up. They are very strong.

 

[nb rob]

Bummer man. I hope you can get it fixed without spending a fortune.
I'm only here to mention, please remove item 3 from that list. Its not safe.

 

[DesertCanyons]

Stripped threads on shock mount

While installing some new shocks I stripped the threads inside the bottom mount on the driver side. ...
...
1. Retap the hole with a larger thread (maybe 1/2" since current thread is M12x1.25)
2. Drill further into the mount and tap the new drilled part with the same M12 thread and try to use a longer bolt which will hold on these new threads.
3. Drill completely through to the other side of the mount and secure with a long bolt and nut.

What do you all think?

That's a bummer. This thread is critical to keeping the shock on tight. I know. I lost this bolt on the road somehow. My fault - I did the install. Then it bent and destroyed the shaft of my ICON 2.5" shock. I drove for a while without the shock and didn't even realize it. Luckily the ICON was repairable locally and the threads did not strip or bend as the bolt fell out.

I suggest you go with #1 and #2 above. Check the size of the 1/2" bolt to verify there will be enough meat left on the little cylinder that is threaded inside. But 1/2" is just over 12 mm.

#3 presets problems with verifying the bolt stays tight. You might need a double nut and lock washer or Locktight. Is there enough room to work on the back side?

Check the bolt often to make sure it's not coming loose later.

 

[klk87]

Thanks for all the replies. Yeah I definitely don't like option 3 either, I am going to try option 1 today.

I looked up the drill size required for tapping a 1/2" thread and it looks like it's 29/64" or 11.5 mm which I don't think is large enough to clear out the existing threads. So I think I'll go up to a 14mm thread instead which needs a drill size a little over 12mm. I measured the thickness of the mount walls and they are a little under 4mm so I'm thinking that I can afford to drill out a little under 1mm.

For anyone reading this in the future that is having a hard time getting the shock onto the lower mount DO NOT try using longer bolts with washers to try to push the shock eyelet on. You may end up with a much larger problem!! Just use a ratchet strap instead.

 

[Bayou_Pro]

That's a bummer. This thread is critical to keeping the shock on tight. I know. I lost this bolt on the road somehow. My fault - I did the install.

Yep it's easy to do. My opinion is that Loctite is your friend and recheck and retorque everything. I use Red on all suspension components and Blue on most other fasteners. Some may shy away from this but I've been turning wrenches for almost 30 years and it's just what I do. I've never run into an issue using it sparingly. I did my lift kit a few weeks ago and every suspension bolt I pulled out had red from the factory.

Glad it didn't mess anything up!!

 

[klk87]

I was able to re-tap the threads in the mount to a 14mm. The only 14mm tap I could find at the store was a 1.25 thread pitch, so I went with it but unfortunately I think it was a poor choice as it's very hard to find any bolts for it. Ended up using this as a replacement bolt:

https://www.oreillyauto.com/detail/...-25-thread-17mm-hex-wheel-bolt/610532/4181405

The threads are in great shape now so I don't think it has a risk of coming loose but it's just a little too long so I am planning to get another one and cut it down a bit. Then stick it back in with some red loctite :gun5:

 

[Jetboy]

I think there was a little confusion on option 3. Drilling 12mm through and putting a longer bolt through would be no problem at all. Cutting off the female threaded mount and just bolting the shock to the remaining tab would not work very well. Sounds like you've got it fixed.

 

[nb rob]

I think there was a little confusion on option 3. Drilling 12mm through and putting a longer bolt through would be no problem at all. Cutting off the female threaded mount and just bolting the shock to the remaining tab would not work very well. Sounds like you've got it fixed.

Drilling through and using a longer bolt creates a prying condition that adds additional forces to the bolt in terms of tension. Shear becomes a factor, even though the shock is seated on the post.

The post with the female thread takes the force in the stock condition and the fastener does not. Bolt shear is minimized. Prying forces are minimized

 

[Jetboy]

I don't think that the longer bolt would make any difference in this setup. The threaded post is taking the entire loading from the shock. The only function of the bolt is to hold the shock in place so it doesn't work it's way off the end. If the bolt were run through the assembly with a nut on the back side it would have the same effect as it does if it's threaded into the post. The post could also be a male thread with a nut on the end like how Toyota used to make them. I really don't know why they're now a female threaded post instead of a male thread. They're all basically the same.

That would be a little different from the standard setup used on most custom suspension setups. Lots of offroad vehicles just use a special double threaded bolt as the shock mount like this:

Seems to work well.

 

[DesertCanyons]

Rear shock pin and 14 mm x 1.25 threads

If the female post were cut off and rebolted it would induce prying on the bolt. Because the post is mounted on the side of the bracket that's welded to the axle, there is a bending action on the post under the force of the shock. If it were cut it would pry on the bolt as the post tries to bend under the force on the shock.

The female post offers more resistance to this same bending action due to the larger diameter of the tube compared to the bolt. The cylinder is wider and has more of a force couple to resist bending, in engineering speak. It's a bit like spreading your stance to resist being pushed over by the wind or someone pushing on you. The wider the resisting feature is, the stronger it is at resisting being pushed over.

I think the through bolt could work if the post and mount were not cut and no welds were cut.

The drill and tap method seems best. I don't think OP, klk87 needed to go larger than 1/2", or 12.5 mm. If the tap hole was still within the same threads it could work if the pitch were the same and the tap were started carefully. The bolt is only needed to keep the shock from sliding off the cylindrical post. I hope your new 14 mm threads work well for you.

When you buy a tap or a bolt you need to verify the bolt and tap are available in the same pitch. Good luck finding the 14 mm x 1.25 pitch bolt. Try searching on Amazon or do a search for a bolt supplier to order the bolts.