Quote:
Originally Posted by mid_life_crisis
Does anyone know offhand what ratio will get an A/T the closest to matching the overall final ratio of a factory M/T?
|
Here are the gear ratios for manual and automatic;
Manual transmissions
I=3.626, II=2.188, III=1.541, IV=1.213, V=1.000, VI=0.767
6th gear ratio, Differential ratio, and engine RPM's at 60MPH.
0.767 @ 4.10 = 2575 RPM's @ 60MPH
0.767 @ 4.30 = 2701 RPM's @ 60MPH
0.767 @ 4.55 = 2858 RPM's @ 60MPH
0.767 @ 4.77 = 2996 RPM's @ 60MPH
0.767 @ 4.88 = 3065 RPM's @ 60MPH
Automatic transmissions
I=3.538, II=2.060, III=1.104, IV=1.00, V=0.713, VI=0.582
0.582 @ 4.10 = 1954 RPM's @ 60MPH
0.582 @ 4.30 = 2049 RPM's @ 60MPH
0.582 @ 4.55 = 2168 RPM's @ 60MPH
0.582 @ 4.77 = 2273 RPM's @ 60MPH
0.582 @ 4.88 = 2326 RPM's @ 60MPH
0.582 @ 5.29 = 2521 RPM's @ 60MPH
0.582 @ 5.404 = 2575 RPM's @ 60MPH
0.582 @ 5.71 = 2721 RPM's @ 60MPH
An A/T 4th gear is 1:1, running 3357 RPM's @ 60 MPH. 5th gear w/5.71 FD @ 60 MPH runs @ 3334 RPM's, so 5th gear is still overdrive, barely, even with the highest FD you can get.
They don't make a 5.404 to 1 ring and pinion, so you can't match a manual's final drive. You can totally out-launch a manual though!
First gear, (launch!) comparisons;
3.626 M/T 1st 4.10 FD = 7101 RPM @ 35 MPH
3.538 A/T 1st 4.56 FD = 7046 RPM @ 32 MPH
3.538 A/T 1st 4.88 FD = 7069 RPM @ 30 MPH
3.538 A/T 1st 5.29 FD = 7152 RPM @ 28 MPH
3.538 A/T 1st 5.71 FD = 7168 RPM @ 26 MPH
Showing approximate redline speeds with each FD.
I'm getting the complete rebuild package with 4.88 gears delivered TOMORROW! I just ordered the entire kit, bearings, seals, shims, solid spacer, and etc. from Spence @ Weir Performance and it got shipped Friday. Here's the price I'm paying for all the parts;
FRS/BRZ 4.88 final $268.70 includes pinion depth shims
Install kit $313.94 (includes all diff bearings, solid spacer with shims, axle seals, pinion seal, pinion nut, gear marker)
ship $20.55
Total $603.19
Installation should be about half that, so roughly $900 - $1000 for everything replaced with all-new parts.
I'm getting this installed Thursday the 15th. I'll post here and let you know it turns out. Tire height for stock size tires, 24.62". Gear calculator website -
http://www.csgnetwork.com/multirpmcalc.html
