Replacing Dodge Roadtrek Front Shock Lower Bolts

[RT-NY]

I am replacing the front shocks on my 1999 Dodge RT 170. I will need to replace the lower mounting bolts--these are SAE 5/16-18 x 1 1/2 fully threaded bolts that screw directly into the lower control arm. The bolts have no grade markings, just a manufacture's mark, a circle with four short lines radiating at the poles. I can find stainless steel bolts of that exact size online easily, but I am wondering if heavier duty bolts would be better for suspension components. Fully threaded grade 8 bolts of this size seem harder to find online, though perhaps a hardware store would have them. Any recommendations?

(I should add that according to the factory service manual, these bolts are only torqued to 17 ft lbs.)

 

[youngnretired]

There's no real load from the suspension or chassis on these bolts, just the load from the shock resistance as the chassis rises and drops. I wouldn't use stainless as that is typically more brittle than steel and I would personally stick with grade 8 hardware. You could probably get by with grade 5 and standard grade, but I wouldn't do it for long term use.

Do you have a company called Fastenall in your area? If so, pay them a visit and they may have what you need, or could possibly order it for you.

If you have access to a grinder and cutoff tool, you could get a bolt that's longer, thread a nut on the end, then cut off the amount of threads that get the thread length back to what you need, chamfer the end of what you cut, then unscrew the nut and you now have a shorter bolt.

 

[RT-NY]

Thank you very much for that advice! The original bolt is 1-1/2" long, but I can get 1-1/4" fully threaded grade 8 bolts easily enough. Because the bolts just screw into threaded holes in the control arm, so they do not need a nut on the other end, and because there is 1/2" or more of extra length that just sticks out beyond the threaded hole when using the original bolt, I am thinking that the 1-1/4" would work fine. What do you think?

 

[youngnretired]

1 1/4" is shorter than 1 1/2", so I wouldn't go that route unless you mean 1 3/4". The trick with the nut on the bolt before you cut off the end of it is that when you unthread the nut from the cut threads, the nut "cleans up" any damaged threads as you remove it. I wasn't suggesting you put a nut of the bolt before installation.

If there's no issue with using 1 3/4" or 2" bolts, go that route?

 

[RT-NY]

I did mean 1-1/4". I was thinking that the original 1-1/2" bolts are longer than necessary because more than a 1/2"--as much as 3/4"--of the nut just sticks out beyond the threaded hole. The problem with the 1-1/2" or longer grade 8 bolts that I have found easily available online is that they are not fully threaded.

 

[youngnretired]

If the bolt goes thru the shock and threads into the lower control arm, are the full threads needed because they are inside the steel tube in the rubber shock mount? like only the last portion of the bolt needs the actual threads.

If the original bolts (if they weren't replaced by a PO) are longer than needed, then you could go with a shorter bolt. Just make sure there is 100% bolt thread engagement with the threaded nut on the back side and it sounds like all would be fine.

 

[RT-NY]

I was thinking that the full threads are needed because the holes in the control arm are threaded and the head of the bolt is right up against the shock mounts (on the right in the first picture) with just a washer, and because the original nut is fully threaded. But, on reflection, I might just be mistaken, and the holes in the control arm are not actually threaded at all, and the bolt is just engaging with threaded nuts welded to the other side of the control arm (in the center of the second picture), in which case a bit of shoulder would be fine as long it is not longer than the combined width of the control arms, the shock mounts, and washer. But even the shorter fully threaded bolts will be fully engaged with the nuts with plenty of slack beyond them.

 

[youngnretired]

I was thinking your shock mount was different, where the bolt goes thru the tube, but in your case, you do need a full thread bolt. I doubt you'll find one that has such a small untreated portion, so full thread is good. And I think you could likely get by with a shorter bolt.

 

[RT-NY]

Thanks again for all your advice!

I am wondering if the reason that the bolts seems to be longer than necessary (in the sense that so much of the bolt just sticks up in the air beyond the nut) is because the "front shock lower mount bolt" was a standard part for Dodge Ram's of this era but not all of them are configured in quite the same way, so some do need a longer bolt. Just a guess.

 

[TX-Trek]

I've used www.boltdepot.com for a lot of hardware on my car builds, especially Grade 8. Might be another possible source for you.

Just my preference, I like using fine vs coarse thread on suspension stuff. There's generally a bit more strength with the fine thread bolts, although I'm sure for your application either is fine.

 

[RT-NY]

Thanks for that recommendation!

If I wanted to use fine thread bolts, wouldn't I have to replace the nuts that, I believe, are welded onto the control arms?

 

[youngnretired]

You would have to remove the nuts that are welded to the control arm if you wanted to change the thread pitch. I see no need for that because the shock bolts aren't seeing a huge load. Just replace the bolt with a new bolt.

 

[booster]

5/16-18 is the standard coarse thread and is extremely common, but in this case it really should be a flange head bolt because the shocks have slots in them and not holes. Any good hardware store should have what you need and no problem going a bit shorter.

 

[RT-NY]

booster - if I use flange head bolts, should I leave off the washer? The original bolt has a regular hex cap with a thick washer. Also, should I torque a flange head differently (perhaps not an issue because the spec is only 17 foot lbs)?

 

[TX-Trek]

Thanks for that recommendation!

If I wanted to use fine thread bolts, wouldn't I have to replace the nuts that, I believe, are welded onto the control arms?

Ah, yes! I forgot about the welded nuts. Anyway, keep it as a source for future needs.

 

[booster]

No washer normally with a flange head. Personally, I like the serrated flange versions as they don't back as they have built in lock washer affect.

 

[otr]

Just an FYI, I use Bolt Depot as a source for all kinds of things like this, especially stainless for bike work. They likely have anything you would need