I bought a 1988 GMC K3500 Duravan. This is an old Ryder Rental truck. The last owner installed a 1995 Chevy 5.7, with a 4l60e tranny. Nothing on the dash works, but the gas gauge. I can live with that. I am going to install aftermarket gauges. The transmission seemed to work OK, but both the electrical plugs on the side were not hooked up. Recently the transmission started shifting out of gear, while driving. It would shift back at a crawl, But just keep kicking in and out of gear. My limited knowledge makes me think there is a problem with the clutch , but I'm guessing. I also wondering if the electrical not being hooked up caused this. If I have the replace the tranny, should I go with another 1995 4l60e, as that is what is in there? The thought of installing a 350 or a 400 turbo, also crosses my mind due to electrical problem, but I am not sure about hooking it up to the 1995 motor. Any advice would be appreciated. Thank you