What auto trans is in my '91 Z28. Is it still a 700R4 or had they switched to the 4L60 yet?

My mind is telling me anything in a thirdgen is a 700R4 but I swear someone told me with an electronic speedo its a 4L60. Then when I looked up my RPO's for something different the trans is listed as "Transmission, Automatic 4-Speed (THM700R4/4L60)

I tried to search but apparently I'm using the wrong terms or no one was dumb enough to ask yet lol.

 

Everything up to late '87 was 700R4, then they installed an aux. valve body and changed the name to 4L60.
Later they made the electronic version and called it 4L60E.

Firebirds got the electric speedo in '86, Camaro in '90.
HTH

 

The 700R4 and the 4L60 are basically the same transmission. My reference only goes forward to 1987. GM started to make changes to the 700R4 in October 1986 starting with an auxiliary valve body and revised fluid passages.

In between these dates, GM introduced a 10-vane pump, new forward clutch and lo/reverse roller clutch assemblies, new pan with a square magnet and improved the reverse engagement feel.

The change in designation from 700R4 to 4L60 occurred in 1990. The OP's transmission is designated as a 4L60.

Edit: I did find reference to changes that date back as early as 1984

 

As others have said..700r4..could have 2:73 rear end..or 3:08 depending on motor...