I've been reviewing this thread in preparation of upgrading my hitch bolts but am wondering if the bolts had already been upgraded by the previous owner since he towed a car. How can I tell which grade is installed? Here is a photo.
Grade 8 Tow Hitch Bolts (https://www.lazydazeowners.com/index.php?topic=29356.msg164693#msg164693)
Never mind, just found the answer. Looks like they have been upgraded so just need to check the torque values.
https://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx
Make sure all the washers are good and none are dished out. When I upgraded to grade 8 there were some bolts too small for the wholes so I replaced everything, Bolts and washers. Yours look good to me.
Jon
Hi Greg. In addition to grade 8 bolts, there are also grade 8 nuts, washers and lock washers. One problem with grade 8 bolts, is that they are so strong they will 'pull through' soft steel bumpers. So On the 3/4" bolts I doubled up the washers for the bolt heads inside the bumper, and outside the bumper. I also used a lock washer.. Tightened as tight as possible with a 1/2" x 18" 'cheater' bar and an air wrench. It better not loosen up! (I check it for tightness about once a year) All of the hardware has the golden (edit) zinc with dichromate coating. (not cadmium). In my TK with the bumper mounted on the extension, I reinforced the extension with additional steel channel and grade 8 hardware also. (reply#7 Thoughts On Towing and Hitch Hardware Reinforcement (https://www.lazydazeowners.com/index.php?topic=28840.msg159538#msg159538)
That was 5 years ago, still tight. If they had loosened I was going to use red Locktite. RonB