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I ordered some firestone 4135 air springs for my (early) 1998 4wd ltd, and took a look under the back to see how things would fit. What I see is that the coil springs have about 9" of empty space inside, and they do not have the cone shaped upper spring seats inside the coils, only the large, segmented axle stops next to the coils. The spring seat needs to be cut down during most air bladder installs. Many are calling it a "bump stop", but Toyota calls it a spring seat. The coil upper cradle has a very large opening, almost as large as the coil ID so there is really nothing for the bladder to push up against. It seems like I am either missing the coil spring seats (bump stops) for this vehicle, or this is the wrong air spring kit.
The runner was a lease vehicle I bought used. It seems unlikely that it would have been modified, and I have found no mods in any of the work I have done on it. Can someone with the same year verify that it should have the cone-shaped spring seats. All the pics I see are typically 2wd non-ltd models, which have some different suspension parts. After the weekend, I will give the dealer & firestone a call to get the low down.
There is no record of it having gone in for the spring recall. I just ignored those recall notices after Toyota said the 4wd model was only included to avoid confusion, and no parts would be replaced.
I have an unused Firestone 4135 kit that I'm putting on Ebay this week. I bought the kit late last year but decided to install rear air shocks instead (the setup works great).
OK, I spoke to Toyota, and this model 4runner does NOT have the cone shaped spring seat/bump stop. They did not have any in stock to look at. There is a chance that the frame is the same as other 4runners and they would fit fine, but I'd need good photos & measurements to be sure of that.
When I spoke to a Firestone tech, he was unaware that some models of 4runner do not have the spring seat, but he thought the air bladder would work anyway since it is not designed to increase in length. Instead the bladder is supposed to expand in diameter and force out slightly between the spring windings to stiffen and expand the spring. He said that it is common to have an inch or more gap above or below the air bladder after it is installed (I estimate a 2" gap would exist), and that the bladder would find its own 'sweet spot' inside the coil after some use. I'd feel better about all this if there was something in place to prevent the bladder from walking out the top of the coil.
I installed the air springs and new shocks in about 3 hours. After taking a closer look at the upper spring cradles, I could see the opening in the frame was about 1/2" smaller all around than the springs so this lip should prevent the bladders from pushing up out of the coils like I thought.
Since I had no spring seats/bump stops to modify all I had to do was take off the spare tire, jack up one side, remove the tire & shock. Fold the bottom of the bladder over and push that part between the coil windings. Wiggle it around a bit, fold the top of the bladder over and push the rest between the windings. A little more wiggling and it was in place. There was absolutely no need to unbolt anything more than the shock & tire. I spend most of the time taking off one stubborn shock, and routing the air lines. I chose to route the lines back through the frame rails and tee them together at one side of the bumper. I made a small angle bracket to hold the fill valve.
After driving it around a bit, I would recommend these air springs. Very easy to install on this vehicle, and I like the quick connectors vs the barbed fitting on the competitor product. The 1" sag is gone, but that might have more to do with the new (stock) shocks. The ride is stiff at 10psi, so I probably need to carry a tire pump and a low pressure gauge to make quick adjustments.
08-05-2017, 07:15 PM
