Another 8 3/4 question

[BIGSHCLUNK]

Anybody care to make a calculated guess?
Looked underneath  the Chally she's got the 489 ok . I did not see a tag for the gear ratio. Crate hemi with a 727.
If the tach and speedo are accurate about 3250 R's at 55mph 3700 at 65mph. Thanks

BTW the trans is #'s correct for the car(383 R/T)

[Chryco Psycho]

What size tire ?

[360 'CUDA]

3:23       

[Carlwalski]

26" tire would equate to a 4.40 ratio
27" tire would equate to a 4.56 ratio
28" tire would equate to a 4.74 ratio


Which ever way you look at it, that's some low gearing!!! 


 

[GoodysGotaCuda]

You should really jack the back end up and count the tire rotations per one driveshaft rotation to figure the ratio out, or atleast get an idea. Then we can figure out if you have the right speedo gear. It is also possible if the transmission has been worked on/out of the car that the speedo gear wasn't 'clocked' properly when re-installed...In other words, we dont know if we are working with a accurate speedometer unless you count the ratio, give us the tire size...then you can compare your speedo to the tach. Or pace someone in a car witha good speedo and roughly compare..

We will need your tire size as well..

[heminut]

You can also take it out on a road with mile markers and check for accuracy on the speedo. Watch the 1/10th mile numbers on the odometer and see if the number at each mile marker is the same or if it is changing. If it's off very much you'll be able to tell within 3 or 4 miles. You can also check it by timing it between mile markers. You have to set the speedo dead on 60 MPH and keep it there and time it from one marker to the next. If the speedo is correct it will take you 60 seconds from one marker to the next. To do this you need to be on a highway with a passing lane or one with very little traffic because sure as heck someone will get in your way that is going slower and screw you up.

[BIGSHCLUNK]

Ya know I though about tire size after I did the post..(dumbass me). As for the spin the tire routine #3.23 to 3.55 for example not much differance. I'll get the tire size and post it tonite! THANKS

[GoodysGotaCuda]

Ya know I though about tire size after I did the post..(dumbass me). As for the spin the tire routine #3.23 to 3.55 for example not much differance. I'll get the tire size and post it tonite! THANKS

Given your tire size and maybe 3.23 or 3.55 we can still plug in both and see what rpm your turning and which matches up..

[MEK-Dangerfield]

My guess is a fast running tach, or your speedo gear in your tranny is waaay off. Do you at least know if the speedo is right in measuring MPH?

  Mike

[BIGSHCLUNK]

Ok guys,my tire size in the rear is 245/60/15'  I belive the speedo to be relatively accurate but who knows as for the tach I have no clue, judging from idle rpm I wouls guess so. I can say the car is not a rocket off the line, but will plant your a$$ in the seat if you give a punch in the 20-30 mph range. Cant really do much comparative testing till I get the lower radiator hose replaced. (found a big bulge in it). Got the hose just need the time! Thanks guys I do APPRICIATE all your imput! 

[360 'CUDA]

You could still find the gear ratio by spinning the rear tire and counting full driveshaft rotations.
Block a front wheel, jack up the car so both rear wheels are off the ground and take the car out of gear

Position a rear wheel with the valve stem at TDC and put a small piece of tape on the side of the driveshaft.
More accurate when you spin the wheels all the way around twice.

Spin the rear wheel 2 times and count the u-joint rotation. I look at the U-joint zerk fitting but you can just put a piece of tape on the driveshaft if mufflers are in the way
6 1/2 times around is 3:23 gear.  7 count is 3:55.  almost 8 count is 3:90 ect

Of course, you can only use this method if the suregrip is working 

[Jacksboys]

26" tire would equate to a 4.40 ratio
27" tire would equate to a 4.56 ratio
28" tire would equate to a 4.74 ratio

Which ever way you look at it, that's some low gearing!!! 

After doing some quick calculations and assuming that the speedo and tach are correct, I would have to agree with NZ440R/T on his calculations.

[BIGSHCLUNK]

So are we equating this to a $.10 rear end?? This cars NOT that qwick off the line... 

[Super Blue 72]

So are we equating this to a $.10 rear end?? This cars NOT that qwick off the line... 

   That just puzzles me.  You have a Hemi, right?    You must be used to some fast cars!!!!

I think I have to stop driving Hondas... 

[BIGSHCLUNK]

Ya its got thoses funny lookin valve covers allright! I just wouldn't think a stock 489 would be a 4.10 ratio. Then I spose the gear set could have been switched