If it were mine and it was out of the truck, I would put it on an engine stand and do it the easy way.
Anyhow, I wasn't able to use that tool. The tool took up too much length of the seal. I used a piece of picture hanging wire and I used a screw driver to guide it into the groove. Once started, it took steady tension and a lot of patience. I also had to drop the crank some and use some lubrication.
