1/8 Mile Gear Ratio?

[Potentialmerc86]

I've got an 86GT and I was wondering what gear would be better for the 1/8mi with a stock 5.0 with bolt-ons (3.73 or 4.10). I want to avoid last second shifts near the traps that will hurt my ET. This car seems to pull hard up to about 5400rpm's so that's going to be my shift point. I know there are the 3.73 vs 4.10 threads but most answers are "4.10's rock! or "3.73's kill". In closing, I just want to avoid over-revving or shifts near the traps. Thanks!

[jaidedeye]

4.10's or 4.30's is what i would suggest for an 8th mile stick car

[Potentialmerc86]

What RPM's and gear would I be in going through the traps with either of those ratio's, hypothetically? I know this is tough to answer unless you've kept good records, sorry...4.30's sound good but I have to drive this car on the street a little.

[svo6]

Im guessing 4:30's should put you about mid 3rd gear crossing the traps.

[608]

All MPH are with 26" tires in the 1:1 gear (4th with a T-5 and 3rd with a auto)


RPM 5500 6000 6500

4:10 104 113 122

4:30 99 108 117

4:56 93 102 110

4:88 87 95 103

[4SPDFOX...+1]

With my 3.73s and T5, I can do 90 mph in third gear at about 6000 rpm. With my combo, I trap 82 mph in the 1/8th so I am probably at about 5400 rpm as I go through the 1/8th traps, you will be lower since you have less power so that will be about right for you. With 4.10s you may have to shift to fourth right before you finish so I would use 3.73s. If you had a H/C/I combo the let you rev north of 6k i'd say 4.10s. If you plan on modding the car heavily (heads, cam, intake) then I would go 4.10s and spin the motor. But for a 5400 rpm shift point, 3.73s for sure.

[4SPDFOX...+1]

Im guessing 4:30's should put you about mid 3rd gear crossing the traps.

He will definitely be in fourth with 4.30s and a 5400 rpm shift point. With 3.73s he will be at about 4800-5000 rpm going through the traps.

[4SPDFOX...+1]

Ok I checked it out on the gear ratio/mph calculator at F-body.org. With 4.30s and an average tire you will be at 5500 rpm in third gear going 75 mph (your approximate 1/8th trap speed). With 3.73s you would be at 4800 rpm going 75 mph. If you ever plan on racing the 1/4 mile, you will be past your useable power band when you go through the traps with 4.30s only trapping 94-96 mph (stock 5.0). 4.10s will put you right at your redline at that trap speed, and 3.73s will have you at high rpm but still pulling hard. I say 3.73s. It's not really gonna make a difference. I have a buddy that pulled nearly the same ET and trap speed as me with the same combo I have but with stock 2.73 gears. He actually pulls me in second gear. The only reason to go shorter and shorter gears is to get your 60 foot down as low as possible on slicks. If you are using all-out drag slicks at 11 psi, THEN 4.30 gears would be a good choice because you can holeshot so hard. Aside from that, 3.73s are more than enough and will do exactly what you want.

[Potentialmerc86]

Thanks 4SPD!

[Drg racr]

I'm thinking of going to the 3.90 gear.

[dy85merc]

I trap 89 mph @ 6000rpm on 26" inch tire with 4:10....in 3rd gear.

[Potentialmerc86]

At the moment, it looks like I'm leaning towards 373's. I'm also going to be driving this car a good bit so every bit of mileage helps. The 3.08's are a turd out of the hole and have to go...Plus, I see a lot of 1/4 mile tracks in Florida and we'll be landing there around Jul/Aug.

[2camsam]

I've run my 85 with 4:10's in the eighth. I think it needs at least 4:30's or 4:56 if you are going to stay na. I'll probable add nitrous if I keep the car ,so 4'10's should work good with nos.