Need Help Choosing The Best Rear Gear

Jrodstang87 · Feb 27, 2016

Hi guys, I need some input here. I have an 87 foxbody. HCI with 3.55 gears. It's a weekend toy that I beat the piss out of at the track when I can. I blew up another WC t5 recently, and I am in the process of getting an astro A5. The A5 has the 2.95 first gear as opposed to the 3.35 T5 first gear. My issue is I don't want to hurt my track times by having a longer first gear. Do you think it will hurt? The best I have run is a 13.0 @110 with a 1.694 60' and that was with a badly slipping clutch. Do you think I will benefit going to a 3.73 gear or staying with the 3.55s? I have 26" rear tires. Thanks for any input

Jrodstang87 · Feb 27, 2016

Made a mistake. That was supposed to be a trap speed of 104 not 110

madspeed · Feb 27, 2016

While I'm sure thers a calculator out there, you're probably best to get your new tranny installed then hit the track as is. See whatyour trap speeds and finish line rpms are and post that info up along with the mods done to your car

Jrodstang87 · Feb 28, 2016

There are some calculators out there, but nothing factoring first gear ratio. I was hoping someone had experience with first gear ratios and they could chime in

Jason 302 · Feb 28, 2016

If you're wanting quicker ET's, go with 4.10's. That's what I did and have no regrets whatsoever.

Jrodstang87 · Feb 28, 2016

I thought about the possibility of 4.10 but thought it might be too much gear. What did you have before 4.10s?

2000xp8 · Feb 28, 2016

When I first took my hci setup home after installing a tko600 with a similar first gear (2.87) and 3.73's, I must say, I hated it. Felt like I was in first gear for a lifetime.
Had I not went to a much more powerful setup (that makes a ton down low), I indeed would have went to 4.10's.
The tko600 does have a .64 5th which helps a little too for highway rpm.

If you plan on a power adder soon, i'd say just leave it as is.
If not, I would change the rear to 4.10's.

Jrodstang87 · Feb 28, 2016

Cool, thanks for the input. The car will probably stay NA for the foreseeable future. I will definitely consider the 4.10s. I imagine 1st gear would feel too long with 3.55s and a 2.95 first.

Jason 302 · Feb 28, 2016

Jrodstang87 said:
I thought about the possibility of 4.10 but thought it might be too much gear. What did you have before 4.10s?

I had 3.73's before, I don't miss them. 4.10's rip harder, especially at the strip.

Grn92LX · Feb 28, 2016

Whats your exact hci set up? 4.10's should help most likely, you are probably crossing the traps way too low with the 3.55's. I have 4.30's and they're no where near as bad as you'd think on the highway.

Jrodstang87 · Feb 28, 2016

Afr 185cc heads, 1.7rr, SD friendly cam, cobra upper/lower and all the boltons. 3.55s at the track make it feel like there is more to be had.

Gearbanger 101 · Feb 28, 2016

What do you run for tires at the track and what size?

Jrodstang87 · Feb 28, 2016

26x8.5 et streets- the bias ply not radials.

Gearbanger 101 · Feb 28, 2016

Jrodstang87 said:
26x8.5 et streets- the bias ply not radials.

Well, you could probably stand to go with a little more gear then. The bias ply's will "grow" at the big end of the track, which will change your over all ratio.

Jrodstang87 · Feb 29, 2016

Gearbanger 101 said:
Well, you could probably stand to go with a little more gear then. The bias ply's will "grow" at the big end of the track, which will change your over all ratio.

I never took that into consideration. Interesting. So looks like I might be getting some 4.10s

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