I have a T56 in my 91Z28 and can't stand the speedometer reading 2x the speed I'm going anymore, let alone the odometer racking up 2x the mileage. Is using a dakota digital box to translate the only way to do this? If so which one do I need as they sell several, and could I pay someone to install it?

The Dakota box is one way to do it. Technically it's possible to do it with an adjustable buffer box from truck applications, but I don't feel it'll save you time or frustration.

I changed the rear gears from a 2.73 to a 3.42 and of course my speedo is wrong now, my question is would changing the buffer box under the dash with one from a 85 f body with factory 3.42 gears?
if not then would the vss swap from a v6 car into a v8car?
my car is a 86 ta with the 145 mph speedo

i need a part number for the vss gears. and where can I buy them?

i have a 8ka rearend with a 3.42 gears ( I looked inside).
295/50 r15's on the rear
the car is a 86 trans am with a 350 and 700r4.

No. Put the right speedo gears in your trans.


Same thing.

Dealer. Tech section of this site lists the gears for the 700.

I'm proud of you for checking, honestly. 295/50R15 is a normal height (just under 26" I think.) so just get the right speedo gears for a 3.42 (or 3.45 9-bolt) / 700R4 car.

the dakota box you will need is the SGI 5B box.

I have the dakota digital box that you need with all original instructions. I no longer need it due to my new gauges. Let me know if you or anyone is interested