Transmission only has 1st and 2nd gear

DANIELHODGE

MEMBER
2000 CHEVROLET S-10
4.3L
6 CYL
4WD
AUTOMATIC
146,000 MILES

Okay, originally I bought the truck thinking it needed a new transmission. I replaced the transmission and it is doing the exact same thing as the first one. It will shift from first to second but not to third regaurdless if you do it manually or in Drive. Reverse works fine though. My speedometer does not work. I replaced the VSS with no luck. I also made sure the Vaccum lines are hooked up correctly. So I know it's not the transmission itself nor the VSS (unless it was bad being brand new). The only codes it read is a bad speed sensor but it's new so I'm at loss of ideas. Please help with any information.

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

It's almost certain the shifting problem is related to the system is in fail-safe mode due to the missing speed signal. The computer has to know speed and load to know when a shift must take place. Yours doesn't know speed, so you can figure out the rest.

The issue here is diagnostic fault codes never say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis or the unacceptable operating condition. When a part is referenced in a fault code, that part is actually the cause of the code about half of the time. Mechanics will first perform tests on the wiring to rule that out before trying to sell you a part. You have to look for stretched or corroded connector terminals, grounded or cut wires, and things like that. It is real hard to do a decent diagnosis without having a scanner to view live data while you're working on the problem. Without a scanner, you're just a parts changer, and trying to solve a problem that way gets real expensive.