Dobinsons suspension clunk in the rear after install

Hey all,

Got a Dobinsons IMS kit installed on my 2021 TRD OR LB. Full suspension with new leaf springs, control arms, and did the Archive Garage U-bolt flip.

I am experiencing what I would describe as a clunk when going off small ledges or any kind of abrupt change in ground elevation. I don't notice it when going over more rolling type bumps. Seems to be from the rear only. It's more of a feeling in the truck than it is an audible clunk. Feels harsh.

I am wondering if I just notice this now because the leaf springs are stiffer than stock. I went with the L59-111-R springs because I have a long bed. No weight in the back. This is my first truck with modified suspension so I have no source for comparison.

The other reason why I wonder about the clunk is after the shop did the install work, about 3 weeks later and roughly 1k miles of mainly highway driving (only took it on easy rocky dirt roads one time thus far) I noticed that my rear shocks were VERY loose. I could very easily move them around. Turns out the top nut was very loose. I tightened it up a bit and took it back to the shop and they said the technician "must have forgot to tighten it properly during install"

I really can't say how tight it was to begin with or if it was somewhat tight and then just loosened up over time, but I have heard this could potentially damage the shocks. This makes me wonder if that is why I have a clunk.

Lastly, the next reason I think I may have a clunk is it appears they cut the u-bolts too long and I may be hitting them on harder drops. However, I get the clunk on even small ledges where I should be nowhere near hitting and compressing the bumps that much.

Any opinions? Thank you!

 

If you can easily replicate it (like any time you try) take it back to the installer and have them ride with you

No telling what else may be loose

 

I would buy a torque wrench, or borrow one. Check all the leaf spring attaching bolts (19mm socket) and tighten all the U bolts. U bolt socket size varies by brand. If you can't get a deep socket on the u bolts, then they need to be trimmed with a cut off wheel or reciprocating saw.

 

When I took it back to the shop, I asked them to do a once over and check that everything is tightened up properly since I had the issue with the rear shock. They said "they were able to get more torque out of the U-bolts". I kind of thought that was odd because aren't they supposed to be torqued to a spec, not just as tight as they can go?

When they tightened the rear shocks again, the tech tightened the crap out of them. Definitely way more than the usual method of tightening to where the rubber washer squishes to about the size of the metal washer. The rubber washer was squished to the point of almost breaking. Doesn't inspire much confidence in this shop. I noticed this and took it back and had the shop owner fix it himself.

I do have a torque wrench and they did cut the u-bolts a bit, but very unevenly. Pics below.

 

U bolts are the one thing that can come loose naturally after a lift install. I always recommend re-torque u bolts after 300 or so miles. After being torqued again, they should be good for a long time.

Leaf spring attaching bolts get 89 ft lbs. U bolts are between 85-125 ft lbs, depending on the thickness. I torque u bolts same as leaf spring, 89 ft lbs. Unless otherwise noted by install instructions.

Try adding some weight to the bed like sand bags or something. Maybe you just have a really stiff leaf pack and it needs some weight in there.

 

The shop did re-torque everything when I brought it in the the initial issue of a loose shock.

It is definitely a stiffer spring. I was told to size up one level for Dobinsons leaf packs because of being a long bed. It definitely gave me some good lift. I should measure, but I feel like the stance is a little more raked than factory.

I will throw some sandbags in the back and see if it helps.

 

Check the bottom shock bolt. The bushing in the shocks have some play (normal) around the through-bolt. So when the bolt isn't tight enough, the mounting tabs don't squeeze the bushing enough and the bushing can still move up and down on that bolt. Same goes for the leaf springs. I've had to over-torque those in the past to get them tight enough to stop movement and clunking. Sometimes the aftermarket bushings aren't quite as wide as OEM and just needs a couple more ugga's on the wrench.

 

This seems like it could be the problem. I notice the clunk appears to be from the rear passenger side and after looking at the mounting tabs, the passenger seems to be less compressed. Driver side has a noticeable "bend" to the tabs as if it is cranked down tighter.

The shocks are for 2005-2023 Tacomas and I had read the mounting tabs on 3rd gens are a little wider than 2nd gens.

Two questions about this: So I should not be worrying about a torque spec for the bolts and just crank them down really tight? Second, can I do this with the truck on flat ground or do I need to jack it up before tightening?

 

Oh perfect. Hopefully that's it then. I've had that happen many times on my truck after swapping shocks. Happening right now actually after having my shocks rebuilt about a month ago, gotta deal with that this weekend.

On those bolts, since they are acting like an axle and the tightness of the bolt really doesn't effect it's function, yes you can safely over torque a bit. On something like U-bolts or bumper bolts, where the bolt is holding something in tension, torque specs are important and should be followed.

You can tighten those while the truck is on the ground. In fact, for pretty much all suspension bolts its best to tighten them once the truck is back on the ground.

 

Not going to touch anything else but the rear shock bottom bolt. I will report, the issue seems less pronounced or even "fixed" with some decent weight in the bed. Like 300-500lbs. This makes me thing the issue you are describing is the culprit. With the weight the shock doesn't have as much play around that bolt as with an empty bed. Makes sense to me? haha.

 

Yes,
But before tightening move the suspension up and down to get the bushings set properly.
I'm running the same Dobinson 111 springs along with their bushings and shackle bolts.
Don't over tighten.

 

Sweet. If you could, how do I know when they are set properly before tightening?

 

I just moved the rear up & down about 5 times.