Piper Jaffray analyst Alexander Potter recommends using today's post-earnings rally in shares of Allison Transmission as an opportunity to sell the stock. The results were due partially to continued growth in the lucrative market for off-highway parts, most of which is driven by frac-related activity, Potter tells investors in a research note. The analyst, however, continues to expect "disruption from electric drivetrains." Eventually this "cyclical momentum will peter out, leaving holders exposed to secular risks," Potter argues. He reiterates an Underweight rating on Allison Transmission with a $26 price target.