Start line ratio .

[bn69stang]

Hey Ross , my tranny is a  T K O  600 / .82  5th  , i went to that tranny from  T K O  500 and that tranny with 3.50 s had an 11.44  S L R  and that was border line to deep for me , hence the change . So with the 600  and  3.70s i have a  10.62  S L R  ,  with the 3.89s  its  11.16     and those two gear sets at 70 mph are about 120 rpm apart with a 27 inch tall tire . So the 3.89s with a 28 inch tire are about the same as 3.70s with a 27 inch in 5th @ 70 mph which is in the 2650 rpm range give or take a bit .. thanks for the input .. Bud

[bn69stang]

So Ross if you feel that your first gear is almost to low with 2.87 - 4.10 s , and considering your cubes and torque , what would you change to ? .  Bud

[65er]

I have 4.30 gears and the TKO 600 in the Galaxie for a 12.34 SLR and I like it just fine.  Funny thing is, when I first put in the TKO I had 4.30 gears and hated them. The new engine likes a bit more RPM and I guess my driving habits have changed over the years.  I have 255/60-15's and my highway cruising rpm was a smidge under 2000.  It's up around 2200 now and the engine seems happier with the increased RPM. 

[bn69stang]

That sounds like some healthy gearing for sure , are you planing on staying with the 255/60-15 s  ?

[65er]

No plans to change any time soon except for when I hit the dragstrip.  I'll have some slicks that are a bit taller than my street tires and it's all calculated for 116 mph at redline in 4th gear with the slicks on.  If I can make 116 in the quarter and cruise the highway at 2200 rpm I'll be pretty happy with that.

[bn69stang]

Yes for sure Wade , im thinking of a second set of rims as well , and another set of gears but for now its the 3.89 s and 255/60-15s  , and just see how the car the motor changes and tranny change .. Bud

[bn69stang]

Tire height is set at a 26"  standard , and for every inch of tire above this standard is like a .06 gear change , so a  28" tire with  3.50s  become  3.38s  and  3.70s = 3.58s  and  3.89s  are  3.77s .. hope this helps you guy s , it answered mine .. Bud

[My427stang]

Sorry, I didn't see your post the other day.  I don't consider mine too low at 11.79 and a 275/60-15, I am just not sure I would go lower.  Maybe a 4.33 with a little less torque, but beyond that I don't think there would be a benefit.

The issue with a 4.11 and your .82 though is that 5th gets steep for me.  I really like my 2.63:1 on the highway, even at slower speed, if I was 3.37 I am not sure it would be tall enough for me.

[bn69stang]

Thanks Ross , im going to start with my 3.89s and i think i will purchase some gear in the range of 4.11 - 4.30 range , i did go to a 275/60-15 and its actually 27.7 inchs tall .. Bud

[My427stang]

I went from a 3.70 to a 4.11 and loved it, that's 11% change, 3.89 - 4.11 is only a 5% change, my guess is the 3.89 should do great.

My 3.70s certainly had no issue accelerating, where the 4.11 did better was in 5th, it allowed me to slow down a little LOL  That was a 10.61 SLR , same tire size.

So your 11.16 should be real nice with the 3.89, in between the two and still gives you a 3.18 in 5th. 

Let us know how you like it!

[bn69stang]

Yeah im excited to do the changes and see how i like the car , and will keep you posted Ross , thanks for the feedback .. Bud