This Gave Me a Bit of a Scare

Installed my suspension upgrade a couple weeks ago (shocks, leaf pack and U-bolt flip kit). After getting everything together and letting things settle, realized I needed 3 degree shims for the rear axle to get my driveline angles smoothed out. Got the Toytec shims and decided to install them today.

All was going smooth, got the leafs on the driver side separated from the axle and went to remove the center pin. Nut came off easy, but I couldn't push out the bolt. The bolt would rotate but not move vertically. Broke out the big hammer and that solved the problem. What came out is in the photo above. The pin was in the process of shearing completely through, primarily between the overload leaf and the leaf above. While it might not be completely evident in the photo, there is also deformation in the bolt between the two leafs above the overload leaf as well, but not as dramatic.

I am using a Archive Garage flip kit, and I had torqued the U-bolts to 80 ft-lbs according to the instructions after the truck was back down on the ground. The instructions say to check U-bolt torque after 100 and 500 miles. I ended up re-torqueing the U-bolts after about 30 miles, not wanting to be that guy that lost his rear axle, and the nuts on the front of the axle on both sides probably took another turn or so to get them back to spec. I was probably at around 60 miles when I went to install the shims.

I should note that between 0 and 30 miles, I bombed about 20 miles of gravel roads trying to find as many washboards as possible and hit them at around 50 mph, to see if all the money I had spent was worth it (I was relatively happy). Between the checking torque and today, I also loaded the bed down with about 500 lbs of weight and did the washboard quest again.

It might be that the center pin was substandard, but I am thinking that the main culprit was putting my rear suspension under too much stress before the U-bolts had fully stretched and settled. The pin on the passenger side was slightly deformed as well, but not to near the degree of the driver side. It is noted that I did snug down the nuts on the center pins before installing the leafs, so don't think a loose nut on the center pin was the problem (they were still snug when taking the nuts off).

It has also occurred to me that a bit of rust between leafs (added friction) is probably a feature not a bug, when it comes to keeping the center pin intact. I should note that the center pin on the passenger OEM pack, that had 3 winters and 30k miles on them, was not deformed when I removed it, but it was a bit rusty. I also checked torque on my OEM U-bolts when I first got the truck and again for every oil change (took about 2-3 oil changes before the U-bolts stopped stretching).

After getting everything back together today, I went for a short drive around the neighborhood and then checked torque. The front nuts took about a half turn on both sides to get things back in spec, so one should really check torque more often than 100 miles, and should also take it easy until things do settle down.

As an aside, I also ended up stripping the first pin I installed that came with the Toytec kit, when trying to get 33 ft-lbs on it (with the springs still clamped together, but the nut was lubed with cosmoline). Found the spec online and wanted to make sure the pin was properly torqued this time. Got a replacement from Napa, that did seem to have a higher Rc rating (based on feel of how quickly torque was reached), so I am a bit suspect of the Toytec hardware. For peace of mind, I masked off the leafs and spray painted a vertical line on them, so I can visually see if the springs start to move horizontally of each other.

 

Interesting.

The U bolts, once torqued down and holding that value, should keep your springs together and from shifting.

I recently installed a Torch AAL on my 'Taco, I misjudged the length of the leaf spring pin for the driver's side and cut it too short. So I had to use the smaller diameter leaf spring pin that came extra in the kit (see attached pic). Note to myself for future reference: Use C-Clamps before removing U-Bolts on driver's side leaf spring, in case the smaller diameter leaf pin fails/failed

 

This second time around, I have been checking U-bolt torque after every time I drive the vehicle. I have require a bit more torque on the front nuts on each side each time I drive my truck, but each time the amount I have to turn the nuts to get to spec is less, so it appears things are tightening up. The rear nuts have stayed torqued to spec every time I check. I think the issue boils down to the fact you can't settle the final location the u-bolts and springs want to take on the axle simply by jumping up and down on the bed and shaking side to side. The only way to get everything to find its happy place is to drive it.

Based on what I have experienced, I would say to check torque on U-bolts after the first drive around the block (with a hard brake or two), check torque again after driving it a few miles around town, check torque again after getting it on the highway for a few more miles, and by that time, you probably are getting close to 100 miles, check torque again. I would do all this before stressing out the suspension off road. To be safe this time around, I think I am going to do the first 500 miles on pavement before I do anything extreme again with the suspension.