Originally Posted by 2007tacoOldLineSt
So...2007 double cab, bought it used with around 12k mileage, it was a little beat up, not to bad, but I did notice the springs are frowning a bit. It seems that this is par for the course, but I havea few questions for those in the "know".
1) At what point is there to much "negative arch"?
2) Can I add a "super spring" or AAL to help bring it back into alignment? Or even a "helper" spring setup as a short term fix?
3) Is it possible to swap out the springs for new ones on my own? ( I am handy, work on the truck myself, etc. but was not sure if any special equipment to switch them out )
It seems the "negative arch" is common, not sure if I should be worried, thanks guys.
There are a lot of the people thinking there is a negative arc on the leaf springs. Its more of an optical illusion due to the springs not being mounted parallel to the ground and the frame doesn't exactly sit parallel either. Since the rear of the spring is sitting so much higher than the front of the spring, the mind tries to make sense of it.
With only 12k miles and an 07, unless the previous owner was hauling full loads daily, I would suspect that its a case of illusion for you as well.
The FSM gives you specs for the height between the axle and the front of the leaf spring. It's a real simple measurement. The center of the front leaf spring bolt minus the center of the wheel (unloaded, of course). You'll get a negative number, which, depending on your model, should be close to -1.5". If you have a spacer lift in the back, of course remove the amount of lift from your leaf spring bolt height measurement.
For 2WD: http://www.ncttora.com/fsm/05+/data/...a/03900210.pdf
For 4WD & PreRunner: http://www.ncttora.com/fsm/05+/data/...a/03900310.pdf
Another indication is the overload spring (I assume 2nd gens have them). If there is plenty of space at the edges between the main springs and the overload, the main springs are still in decent shape. If the overload spring is actually helping to hold up an empty bed, then you have issues.
Anyway, do the measurements and if it is off by much, then yes, your leafs are worn, but personally, depending if you're hauling things or not, I wouldn't worry much about it until the overload spring is close to touching.
There really aren't any specs as to when to replace the spring that I'm able to find, so its mostly just a judgment call as to when the the springs aren't doing their job as they need to. The overload spring is easy to identify and easy to reference for me.
As for your questions...
1. I think when the front leaf bolt is about even than the center of the axle. Mostly a judgment call on how it rides and if you haul things. No one can really answer this for you.
2. Only use AAL for lifting purposes. You'd just be wasting your money to buy one to help sagging springs. (The AAL would be doing the job of the complete leaf springs if installed on bad springs, so would wear out pretty fast.) AAL is meant to assist your leafs, not do the whole job.
3. Fairly easy job if you have an impact wrench and/or the bolts aren't rusted. Many people have had to cut the bolts off in the past though. Step by step guide: http://www.ncttora.com/fsm/05+/data/...6ta/039011.pdf