PSA: Tighten Your Differential Bolts!
10-13-2013, 04:14 PM
#1
PSA: Tighten Your Differential Bolts! When I replaced my Creative Steel differential bushing with a 95A Revshift bushing this spring, I didn't pull out my torque wrench. I had no idea what the torque spec was, and figured I could apply sufficient torque by feel.
That was a mistake. The driveline felt great for all of fifteen minutes before clunk started to set in again. The evidence was clear--I hadn't applied sufficient torque.
From top to bottom: Craftsman Digi-Click torque wrench with 21mm socket, box wrenches that I previously used on the front bolt, and the breaker bar that I previously used on the rear bolts.
Well, a few minutes ago, I finished re-torquing all three bolts with my digital torque wrench. For fun, I started with the bar set to 95 ft-lbs to see if I could estimate how much torque I had actually applied. On the rear bolts, the torque wrench clicked after 1/8th of a turn. That means, even though I felt like I was in danger of breaking the differential ears off last spring, the torque I applied was almost 50% under spec (129 ft-lbs)! On the front bolt, things were even worse--I managed two quarter-turns before the wrench clicked at 95 ft-lbs. That's over 50% off the mark (also 129 ft-lbs).
So what happened? Simple: I was a dumbass for not checking the torque specs. If I had done that, I would've instantly realized that I couldn't achieve the required torque with box wrenches. If anything that I just said registered with any of you, I highly recommend you lower your subframe by a couple of inches and hit those bolts. You might also want to use a paint pen (the kind used on tire sidewalls) to apply a mark that will allow you to visually inspect the torque later. It'll save you time in the long run.
One of the rear differential bolts. White marking applied to allow visual inspection of the bolt. The area looks wet because I degreased the rubber bushing to ensure the paint pen stuck. Tightened to 133.0 ft-lbs (3% extra).
One side of the front differential bolt. The nut on the back face of this ear is also marked. Tightened to 133.0 ft-lbs (3% extra).
On a related note: the front subframe bolt spec is 195 ft-lbs, and the rear subframe bolts are required to be torqued to 141 ft-lbs.
That was a mistake. The driveline felt great for all of fifteen minutes before clunk started to set in again. The evidence was clear--I hadn't applied sufficient torque.
From top to bottom: Craftsman Digi-Click torque wrench with 21mm socket, box wrenches that I previously used on the front bolt, and the breaker bar that I previously used on the rear bolts.
Well, a few minutes ago, I finished re-torquing all three bolts with my digital torque wrench. For fun, I started with the bar set to 95 ft-lbs to see if I could estimate how much torque I had actually applied. On the rear bolts, the torque wrench clicked after 1/8th of a turn. That means, even though I felt like I was in danger of breaking the differential ears off last spring, the torque I applied was almost 50% under spec (129 ft-lbs)! On the front bolt, things were even worse--I managed two quarter-turns before the wrench clicked at 95 ft-lbs. That's over 50% off the mark (also 129 ft-lbs).
So what happened? Simple: I was a dumbass for not checking the torque specs. If I had done that, I would've instantly realized that I couldn't achieve the required torque with box wrenches. If anything that I just said registered with any of you, I highly recommend you lower your subframe by a couple of inches and hit those bolts. You might also want to use a paint pen (the kind used on tire sidewalls) to apply a mark that will allow you to visually inspect the torque later. It'll save you time in the long run.
One of the rear differential bolts. White marking applied to allow visual inspection of the bolt. The area looks wet because I degreased the rubber bushing to ensure the paint pen stuck. Tightened to 133.0 ft-lbs (3% extra).
One side of the front differential bolt. The nut on the back face of this ear is also marked. Tightened to 133.0 ft-lbs (3% extra).
On a related note: the front subframe bolt spec is 195 ft-lbs, and the rear subframe bolts are required to be torqued to 141 ft-lbs.
Last edited by FuzzyLog1c; 10-13-2013 at 04:23 PM.
