Which Tremec TKX Do I Get
I have 27560R15 tires my 3.55 is more like 3.23. Now this is a street car not a track car. I'm kinda indecisive right now and need opinions.
Well you asked for it, lol.
The TKX-ratios are;
2.87-1.89-1.28-1.00-.72 ; and splits of; .66-
.68-
.78-.81
3.27-1.98-1.34-1.00-.72 ; and splits of;
.61-
.68-.75-.72
For reference, my ratios, (IMO, nearly perfect), are;
3.09-1.92-1.40-1.09-.78 ; and splits of;
.62-.73-.78-.72
First notice that the
2-3 splits are the same, and so become the hinge-point for all the rest, up or down.
Next notice the
short 3-4 of the .78, set up for small engines, so the rpm does not drop so far. at 5500 the difference is 165rpm. at 6500 it is 360 rpm.
Overdrive is 65= 2243 versus 1994, so which one you chose depends very much on your cam; as both are pretty low..
Now the thing you are concerned about;
the effective first gears are ; (corrected to a 24" tire)
3.55 x2.87 x24/28=
8.73, and
3.55 x3.27 x24/28=
9.95 . I run
3.55 x3.09 x24/26.6=
9.90 And I can tell you that with a hi-Torque, 430 hp (by the 93mph trapspeed in the Eighth) 367SBM, that I would NOT run any less. I have run a lil less and a lot more, and for my combo, 9.90 is just about right, and that is why it has been this way since about 2005ish.
Now; trap rpm at 60mph, in second gear; the thing I was concerned about;
With 3.55s and 28s your rpms are; 4830 with the 1.89, and 5060 with the 1.98. My cam peaks at closer to 5100, so, of the two choices, I would chose the 1.98.
And second to last, and of real importance to me is;
what is my slowest possible speed. At 700rpm with 28s and 3.55s this comes to 5.72 with the 2.87, and 5.03 with the 3.27s ; at 550 idle-rpm, it would be 4.5 and 3.9, now you are getting close to walking speed.
And finally;
My Opinion
Since, your lowest in-gear speed is not low enough to walk/parade at, and
since your rpm at 60MPH in Second gear is only 4830/5060, and
your rpm in overdrive at 65mph is only 1994/2243
If it was mine;
I would swap the 3.55s out for 3.91/4.10s, and run the 3.27 trans because;
With the 3.91s;
If I can idle that engine down to 550 in gear, that will be 3.58mph. and
60mph in Second gear is 5574. and
65mph in od is 2200, and
I don't have to put up with that short-fourth.
Your starter gear would be;
3.27 x 3.91 x24/28=
10.96 corrected to a 24" tire. I know what yur thinking and by the math, you are sorta right. But in practice, you will love it. And besides, with a 414stroker at WOT, you will be spinning the street tires all the way to 60 mph, and beyond, anyway. But even better is, when you go to take off, you can almost just put it in gear and drive.
In mine, I just give the heavy stock flywheel a lil blip, ease the pedal out, and go. If you were in a car in the next lane at a stoplight, you might not even catch that my car has a manual trans. There is none of this Mustang slip it halfway to next Sunday bs.
Just blip,slip,and Zip
I think you got stuck on something; you say you don't care about the splits but check this out.
2.87-1.89-1.28-1.00-.72 ; and splits of; .66-
.68-
.78-.81
3.27-1.98-1.34-1.00-.72 ; and splits of;
.61-
.68-.75-.72
Taking off normally, revving to say 3000 for the 1-2 shift, the drop into Second will be to;
3000 x.66=1980 with the 2.87 trans and
3000 x.61=1830 with the 3.27
You got no TC to multiply your torque, so at these rpms your 414 will need some grunt, and that is where the 3.91s come in, multiplying whatever is coming out of the trans by 10% more than the 3.55s would. Cuz let's face it, it's a Mopar; you don't really want to rev it to 4000 to put it into
Second, while just tooling around
,.... like one of those other cough-cough, small-block, classic, also-rans; now do you? lol
IMO, the splits are more important than the actual numbers.
