speedo recalibration

[canadianregal]

Im planning on taking teh 3:42 out of my s-10 and putting them in my regal--anyone know what i have to change to get the speedo to read correctly?
thanks

 

[canadianregal]

set now

currently have stock gears--2:41 i think

 

[Quick6'n'-K.C.]

Change the speedo gear in your automatic transmission. GM designates them by color as to what gear ratio you have.

You also might want to factor in what size tire you will be running, if you run a taller tire the speedo will be off a certain percentage.
I would use a tire calculator on this site to find out how far off it will be depending on what size tire you plan to run.
Stock is 215/65/15

BW

 

[canadianregal]

speedo

Thanks--Exactly what i needed

 

[canadianregal]

GM gear colors

Does GM have a chart or is there one here to match tire size with gear ratios
Plan on using bfg TA 265-50-15

 

[turbo2nr]

1987 Chebby Monty Carlo SS used a reduction box under the hood, about 15% was added to the speed.

I tried a 4.10 rear gear (long story) and I had to take apart the box and flip around the gears so it subtracted 15%. Easy to do.

Last time I checkd (one year ago) GM still sold the box.

Splices right in by the fire wall.

Add or subtract about 15% with the Monty SS box. It was around $69.00

 

[canadianregal]

speedo

thanks turbo2nr
ill look into that--im switching tires from 195-75-14 to 265 - 50 -15 and switching rears from 2:41 - to 3:23---im not sure how this will all work but with the formulas i got from here i should be able to figure it out
the tire change is very minimal in OD so i just have to figure out ratio change.
Ive changed rear end gears in my tractor trailer so i should be able to figure it out---of course the truck was easy--LOAD it up on the puter...
Thanks for the info