95 Lumina Speedo problem

Guys, I did a search and found a few "leads"...just checking if there's anything else. I bought a scrap Lumina...I work at a wrecking yard, and do alot of work on the 3100's. It was a deal at $200. Replaced the heads and intake gasket, mtr runs great, but when I went for a cruise the speedo wasn't working all the time...very intermittent... in turn the trans wasn't shifting right. I've replaced the "trans whatever" sensors before and it fixed this problem. Plenty of these in the "yard" so no money involved in changing parts, while troubleshooting. Didn't work this time...as I read here, could it be the computer? I've owned a few Monte Carlos in the last 10 years, so I'm real familiar with these engines, just haven't seen this yet. Thanks for any help.

Most likely the speed sensor. I believe it's on the passenger side near the CV axle on the transaxle. If that's replaced with a known good sensor, check your wiring. I believe that GM still used the 4k pulse/mile sensor, so check that with a voltmeter.