I have an 87 Wrangler with the terrible vacuum actuated front differential. Sometimes it works sometimes it doesn't. Every once in awhile it won't come out of four wheel drive and other times it won't go in. Right now it will go in and out of four wheel drive but the light won't go off. I replaced my shift motor and it will hold vacuum. I'm in need of a solution. I was thinking of installing the bds rock lock. Suggestions would be appreciated.