Optimal 1st gear ratio?

[Jim_PA]

I'm looking at either a GTO or F-body T56. It seems to me the GTO ratios would be pretty good with 3.73's or 4.11's.

I'm almost thinking I'd want 4:56's with the F-body T56

4000lbs, LQ4 -> Hoping for 450 FWHP from the LQ4 with 243 heads and Lunati 227/231 @.050 with .650 lift. on 112 LSA -- Advertised 2200-6800 RPM in an LS1

Current gear ratio is 3.73 with 26" tires

GTO T56:
2.97:1 2.07:1 1.43:1 1.00:1 0.84:1 0.57:1


F-body T56:
2.66:1 1.78:1 1.30:1 1.00:1 0.74:1 0.50:1

What would be an optimal gear ratio to use with either trans for launching, and which set of gears do you think is better?

2.66 is my current 1st gear ratio with the Super T-10, and I know it's not optimal for launching, but I'm not sure how high I want to go.

Thanks

[cableguy0]

With the overdrive being as steep as it is in those units you can get away with a ton of gear. I know you arent worried too much about mileage. I would go with a minimum 4.10. even a 4.56 wouldnt be bad but you would be through the gears pretty quick. Your best bet is probably to mess with one of the gear ratio calculators and see what rpm you will be turning in each gear. This one will help because you can enter all gears at once. http://www.f-body.org/gears/

[71chevytruckguy]

Another gear jammer, awesome! Couple questions, 1/8 or 1/4 mile? Track only or street use? IMHO with the stick, the more gear in the rear the better. Also, with more gear i think its easier on the drive train expect the axle shafts of course. Less force to get it moving if that makes any sense.

I'm currently running a 5.38 rear with a m-20, 2.52 first for a total ratio of 13.5576. Last season i was the same trans with a 4.88 rear, total of 12.2976 I've noticed a HUGE difference coming off the line with the 5.38's my 60ft's have dropped a whole tenth. From 1.69-1.72's to 1.58-1.71's. Also pulls much better all the way round. I'd like to go to 5.57's but i'm afriad i'd be headin through the traps on the rev-limiter, I shift at 6200.

Just off the top of my head with out any figured, I'd say f-body t-56 with a 5.13 or 4.88. Here's some good reading I found to help ya compare the difference in the two yours and other trans. Chris.
http://www.5speeds.com/ratios.html

[Jim_PA]

Thanks guys - This is for 1/4 mile use, maybe 2-3 times a year. Otherwise, it's a fair weather driver when I don't need to shuttle kids around.

I'll play with some more calculators, but cruising around at 2000-2500 or so RPM at 70MPH is almost as important as coffee-spilling acceleration.

What I was trying to judge was how low of a first gear can I go (and with what rear gears...) and still have first gear useable. I'd prefer not to end up with a 10MPH 6500 RPM first gear

[mongoose]

plug in all the info you can and give her a go..

http://www.car-videos.net/tools/speedrpm.asp

[Jim_PA]

I feel like a 4.11 switch isn't enough to amount to much of a difference, and a 4.56 is putting me in dump truck territory


This is the GTO trans...

I hope this comes through in the copy/paste legibly...

3.73:

1 2 3 4 5 6
0 0.0 0.0 0.0 0.0 0.0 0.0
500 3.4 4.9 7.2 10.2 12.2 18.0
1000 6.9 9.9 14.3 20.5 24.4 35.9
1500 10.3 14.8 21.5 30.7 36.6 53.9
2000 13.8 19.8 28.6 41.0 48.8 71.9
2500 17.2 24.7 35.8 51.2 61.0 89.8
3000 20.7 29.7 43.0 61.5 73.2 107.8
3500 24.1 34.6 50.1 71.7 85.4 125.8
4000 27.6 39.6 57.3 81.9 97.5 143.7
4500 31.0 44.5 64.5 92.2 109.7 161.7
5000 34.5 49.5 71.6 102.4 121.9 179.7
5500 37.9 54.4 78.8 112.7 134.1 197.7
6000 41.4 59.4 85.9 122.9 146.3 215.6
6500 44.8 64.3 93.1 133.1 158.5 233.6


4.56
1 2 3 4 5 6
0 0.0 0.0 0.0 0.0 0.0 0.0
500 2.8 4.0 5.9 8.4 10.0 14.7
1000 5.6 8.1 11.7 16.8 19.9 29.4
1500 8.5 12.1 17.6 25.1 29.9 44.1
2000 11.3 16.2 23.4 33.5 39.9 58.8
2500 14.1 20.2 29.3 41.9 49.9 73.5
3000 16.9 24.3 35.2 50.3 59.8 88.2
3500 19.7 28.3 41.0 58.6 69.8 102.9
4000 22.6 32.4 46.9 67.0 79.8 117.6
4500 25.4 36.4 52.7 75.4 89.8 132.3
5000 28.2 40.5 58.6 83.8 99.7 147.0
5500 31.0 44.5 64.4 92.2 109.7 161.7
6000 33.8 48.6 70.3 100.5 119.7 176.4
6500 36.7 52.6 76.2 108.9 129.7 191.1

[Super73]

Keep this in mind also.. Just because it has a taller first, doesn't mean it will go slower. Another thing that might be considered is rpm spread between the gears. Keeping the motor in the RPM in which it makes it's most power.


One question I also have for you.. Where did you get those T56 numbers for F-bodies?? Are you aware there is a difference in gear ratio between the < 97 and 98+ transmissions? I think your looking at the < 97...

[Jim_PA]

Originally Posted by Super73

Keep this in mind also.. Just because it has a taller first, doesn't mean it will go slower.

How so? - because the engine isn't bogged down as much on the higher gearing? I was thinking it was a more polar relationship.

I got them from here: http://www.ls1tech.com/forums/manual...-body-t56.html

[swb85]

Originally Posted by Super73

One question I also have for you.. Where did you get those T56 numbers for F-bodies?? Are you aware there is a difference in gear ratio between the < 97 and 98+ transmissions? I think your looking at the < 97...

The '94-'02 fbody t56 all share the same gear set. The '93 is the only odd-ball, and it has the same ratios as the GTO trans with the exception of 5/6 which are .80/.62 respectively.

Jim-
With a 4k lb truck, you're going to want a lot of gear to get you off the line. If it were mine I'd run 4.56 with the fbody trans if you are sticking with a 26" tire.

[Jim_PA]

Either way, it will be 3.73's for a while. I'm mainly trying to decide between F-body or GTO gearset. for best overall performance.

[Jim_PA]

That would put me at 220MPH in 6th gear at 6500 RPM. Perfect!

I was hoping I could get away with a deeper first gear, and no gear change, but things never seem to work out that way!

It looks to me like these are my choices....

3.73's and GTO (if not planning on re-gearing)

Or 4.56 and F-body (the numbers definitely look better, I guess I just need to stop whining about spending money )

Then again, F-body T56's seem to be much less expensive than the GTO version, probably due to age and production numbers... so the end cost might not be all that much more.

[swb85]

Originally Posted by Jim_PA

Then again, F-body T56's seem to be much less expensive than the GTO version, probably due to age and production numbers... so the end cost might not be all that much more.

There aren't as many GTO trans floating around, plus they have triple cone synchros (better synchro/blocker design). You're going to pay for a GTO trans if you can find one......

[hotrod 80]

I'd go 4.56 and F-body . If it's too much for you move to a 28" tire . They seem more avalible down here .

[Jim_PA]

Originally Posted by hotrod 80

I'd go 4.56 and F-body . If it's too much for you move to a 28" tire . They seem more avalible down here .

I'm almost certain to do that at this point. I didn't realize the GTO transmissions were such an expensive piece.

I have seen some going for $800-$1800. I'm wanting to go through LKQ again, because they treated me so well with the LQ4. Just a waiting game for buying from them with something so... "old"

[Jim_PA]

Originally Posted by swb85

There aren't as many GTO trans floating around, plus they have triple cone synchros (better synchro/blocker design). You're going to pay for a GTO trans if you can find one......

$2500 + core was all I've found so far

[Jim_PA]

Scored a set of 15 yr old un-used Zoom 4.56's on eBay for $44 shipped today. Should work ok, right???