i always just assumed i had 3.73's. too cold to go outside now and look around for numbers and codes. sound about like 3.73's?

1650@65
1700ish@70
1850@80...

3.73's right? BTW its got a 48re. thanks

 

that's just about where I'm at and I have 35" tires. You might have the 4.10 then.

 

Look in your glovebox, and there is a little sticker inside. It will tell you exactly what you have.

 

Assuming a 0.69 overdrive ratio on the 48re, with 37" tires it works out to be 4.04 for the rear axle ratio, so I'm guessing you have the 4.10s.

That is assuming of course that you are actually traveling 65mph at 1650rpm. If your speedo is off, then the calculations will be off as well.

EDIT: OK, I take back the above numbers. Based on the 65 @1650 number, you work out to 4.04.

But if I use the 80 @1850 number, I get 3.68.

So you'll have the check the tag in your glove box, then check your speedo.

 

i was goin off the speed my outlook monitor gave me, its set to supposedly be correct with the 37's

 

If your tire is 37" tall and you have 3.73s, then at:

1650rpm = 70.5mph
1850rpm = 79.1mph

with 4.10s:

1650rpm = 64.2mph
1850rpm = 72.0mph

This is still assuming the 0.69 overdrive ratio (which I got from the 47RE, so I'm not sure if this is still accurate)

 

BS. Your speedo must be off. Use a GPS to get your actual speed. Larger tires never roll out to be the size written on the side.

My 35" tires actually mesure out at 33.5". Thats what size I punched in my smarty to get the speedo and GPS dead on.

Rockitboy you have 3.73's. I bet you $$$ on it.