tcwc

First off.... THANKS PX429!!!! I asked the question about gear awhile back. Anyhow, using the link PX provided .. I ran the numbers.

The reason for my original post (awhile back) was that it seemed like I was running out of RPM's very quickly in the lower gears (more than I remembered from my 82,83,84,85 and 87). I also thought my speedo was off (reading too low). Anyhow (other then me thinking my speedo was reading too low...which would be just the opposite according to an earlier response). I think my '86 has either 3.73's or 3.90's in the rear.

I did the math (and tested it while driving) for both 4th (1:1) and 5th (.65:1?). Both come out somewhere between 3.73 and 3.90. I guess I can take 'gears' OFF my list of 'things to do'. Apparently they are already there from the previous (or previous/previous) owner.

Like I said, I thought it was 'quick' off the line. Not I don't know weather to be disappointed that I can't see (feel) the difference or be happy that I don't need to spend the $$$ to get them changed!

Anyhow, this add's to my (in my opinion) 'bargain' car I got for $1700!

PS..... Now I can't even run a post here saying 'I got my gears in!' LOL.

Thanks guys for a great forum! Even when you don't think you'll learn something....you do!!!!!!! ;-)

Goosepoop302

i feel the same way i belive my car has 3.73 in them when i bout it. anyone know what my rpm sould be at while going 60 in 5th?? (with 3.73 gears

tcwc

Calculator

According the the numbers I plugged (for your setup). 60MPH, 2.43 gear ratio (read the instructions .65 (5th?) x 3.73), and a 26" tire diameter (I guessed at this for you). You should be at around 1900 RPM (if you DO have 3.73 gears).

Thanks again to PX419...

nitrous_bob

where are you getting 2.43 from????

the od is .068:1

at 75 in 5th my 4.10's turn about 2500

i still get 21.xx mpg

PX429

No prob

tcwc

I doubt that OD is .068. .68 maybe ( I may have been wrong to use .65). Anyhow, do the math. .68 x 3.73 = 2.54. According the the calculator, this is how you figure 5th plus your rear gear.

(If you have a .068 5th, I get you get GREAT gas mileage!!!!) There again, maybe I'm reading something completely wrong...(which wouldn't be a surprise!)

Anyhow, with the new numbers( my mistake) Goose should be close to 2k rpm at 60, in 5th, with 3.73 gears.

Just my 2cents

tcwc

Goosepoop302

hmmm i think im at about 1800 or so??? would a better MPH be better to test that out with?

tcwc

I might have gotten myself into a pickle here.....

But If you check out the 'Calculator', it should take into account all MPH (assuming the calc itself is right).

I found a simular formula (I broke it down by doing the math) from Edelbrock and the numbers matched the above listed calculator (posted by PX429). So I assume it's accurate.

Anyhow, I assume someone (during the life of my car put 3.73's or 3.90's in it). I'm happy !!!!!!!!! ;-)

Goosepoop302

sorry im retarded but that thing of the bottom of the calc got me confused .. do i put in 3.73 or do i take 3.73x.68>

killerbracing13

Easy way to tell ratio is to jack up the *** of the car. Chalk mark the tire, and the driveshaft. Turn the tire one revolution while counting the times the driveshaft comes around.