3t40 final drive question

[wi_corsica]

Both 89's have the 3.18 ratio, meaning about 3K at 70mph.

If I wanted to get down to the 2.84 or the 92/93 v6's 2.53, would that be doable by replacing the drive and driven sprocket, or would one be better off swapping a whole tranny?

[seabass1858]

what about the drive ratios of a 90-91

[wi_corsica]

90 91 have the 2.84 which is roughly 2700@70, otherwise the 2.53 gets it down to about 2400@70

[indygurl]

my indy i believe has the 3.33 ratio.. right??? which would be roughly what??? would love to learn more about my indy.

[3X00-Modified]

I do not belive the Indy is a true 3.33... I think its like every other Beretta out there where it uses the highest ratio diff but then overdrives it from the torque converter to the trans making the ratio 2.97 final drive just like the 4t60e. Its a 0.89:1 ratio from the engine to the trans.

Internal gears the first gear for a 3t40 is 2.84:1 second gear is 1.6:1 and third is 1:1

I've posted this before but it shows the final drive in each gear for each diff combination and the two transmissions.

[wi_corsica]

I am familiar with the 3 speeds in terms of the RPO F16 F17 and F75, which I was looking online at another site (cavy) they were talking about "effective" ratio, which would be the 3.33 you are referring to as using the 2.84 Final F17.

And I saved a copy of a gear/speed/rpm program I found a few years ago, that's how I know that each of those ratios brings the RPM down about 300 at 70.


GearCalc v2.0.0.3 Copyright ©2001, Peter Ogden
Gear Ratio, Speed and RPM Calculator

Gear set: Manually entered values
Gear 1 2 3 Final
Ratios: 2.840 1.600 1.000 2.840

RPM Limit: 6000
RPM @Peak Power: 3200
Tyre Size: 185/75 x 14
Tyre Diameter: 24.93 in
Tyre Circumference: 78.32 in


Gear Mph per 1000 RPM Mph @3200 RPM Mph @6000 RPM
--------------------------------------------------------
1 9.20 29 55
2 16.32 52 98
3 26.11 84 157

Mph RPM (in Gears)
-------------------------------
1 2 3
-------------------------------
5 544 306 191
10 1087 613 383
15 1631 919 574
20 2175 1225 766
25 2719 1532 957
30 3262 1838 1149
35 3806 2144 1340
40 4350 2451 1532
45 4894 2757 1723
50 5437 3063 1915
55 5981 3370 2106
60 3676 2298
65 3982 2489
70 4289 2680
75 4595 2872
80 4901 3063
85 5208 3255
90 5514 3446
95 5820 3638
100 3829
105 4021
110 4212
115 4404
120 4595
125 4787
130 4978
135 5169
140 5361
145 5552
150 5744
155 5935

Gear Change RPM drop (change @3200) RPM drop (change @6000)
-------------------------------------------------------------
1 -> 2 -1397 (to 1803) -2620 (to 3380)
2 -> 3 -1200 (to 2000) -2250 (to 3750)

[3X00-Modified]

2.97 is your final, not 2.84. 2.84 is the ratio on first gear only. So in Third gear you have a 2.97:1 ratio.

3.33 x 0.89 is 2.97 thats how you get your Effective ratio.

[wi_corsica]

So regardless of what the gears and ratios are and how to determine ratios and what it all means, The original question was Can one reaplace the drive and driven sprockets to change the ratios or just swap out the whole tranny?

[Koots]

Which RPO code means what? in terms of 3T40 gearing ratio?

I've got to write down my RPO's!

Maybe I can get a bit more performance out of my base 95 Corsica 2.2 LOL

[wi_corsica]

For the 3T40 this is what I know from my observations:
F75-3.18 used on 88-89 2.8, ALL 2.0/2.2
F17-2.84 used on 90-91 3.1 (and some 92 3.1)
F16-2.53 used on 92-93 3.1

Other ratios for 5 speeds (I think) that I got off of compnine (incomplete list! I know I am missing most 94-96)

FQ2 final drive ratio 3.48
FW7 final drive ratio 3.83
FX1 final drive ratio 3.94
FX8 final drive ratio 3.61
F71 final drive ratio 2.44

[Koots]

I've already got the lowest geared out of the most common available transmissions.

I'll stick with it, as I doubt I'll find an Indy transmission around here LOL. I'm lucky to see a Beretta around here.

Thanks for the info guys.

[3X00-Modified]

I didn't think they geared the 3t40 that far down for a 3.1...

And the answer to your original question is yes, I have a 3.69 effective ratio in my car and it came stock as a 2.92 effective.

The differentials available for the 3t40 are as follows

3.33
3.06
2.84

And you have a choice of these three combinations of drive/driven sprockets

driven divided by drive gear Larger gear in front aka on torque converter lower effective ratio, larger gear on rear higher effective ratio.
33/37 = 0.89:1
35/35 = 1:1
37/33 = 1.12:1

That gives you 9 choices of ratios.
3.18
3.43
3.73
2.84
3.06
3.33
2.53
2.72
2.97

Do the math of what diff you have, being 3.18 as you said its a 2.84 differential with the 1.12:1 drive/driven combo, if you switch to the 35/35 you'll have 2.84, or 2.53 if you go all the way to the 37/33

My old stock setup



My new setup

[wi_corsica]

My 92 and I think both my old 93 and my aunt's 93 were all 3.1's and I think they all had the F16 RPO. Those trannys would be model LFC. I saved all the info on RPO's when Compnine was in the old format. Let me dig that up:
For 1992
144,228 52,179
F16 124,267 Corsica, 23,374 Beretta
F17 6 Corsica, 14,084 Beretta
F75 18,331 Corsica, 7,634 Beretta

I left out all the manual tranny's and engine info.