LT1/TA

Hey guys,I have an 88 with an Lt1/T56 and 4.56 gears.I was thinking of changing my gears to 4.10 or 3.90. I had a 94 formula Lt1/T56 and it had 3.42's and I changed them to 4.10's.I loved the 4.10's and I also like the 4.56's
but I was just thinking of changing the gears.

Bullydawg

iTrader: (7)

I run 3.89 in my Formula with a 9"/T56.

Galaxie500XL

iTrader: (1)

I’m in the process of gathering the parts to do a T56 swap in my L98 IROC..are you happy with the overall performance of the 3.89 gears? Many here suggested 4.10, but I’d prefer just a bit more fuel mileage if it doesn’t hurt the overall performance severely going with a 3.77-3.89 gear.

Bullydawg

iTrader: (7)

I think they are perfectly fine. I am going to install a procharger, so I based the gears off gas mileage and 4th gen RPM assuming a trap speed.

My Ls1/T56 Iroc has 4.10 gears and they are pretty nice as well! I don't think you will be disappointed with either. I was sway to 3.89 if gas mileage is of any concern.

Galaxie500XL

iTrader: (1)

This is exactly what I needed to know..thanks!

tom86iroc

iTrader: (1)

with the 6 speed and 3.90's im doing 70-80 at 1800 so you could go higher and still have great gas mileage lol

Drac0nic

I'll give 2 points of advice on this.

1-Be sure you know which T56 you have. Some have different ratios, and you may want more or less gear. Be aware of it for comparisons
2-Go find a gear ratio calculator online.

Galaxie500XL

iTrader: (1)

Both are good suggestions. My T56 came from a ‘94-‘95 F-body, and has the taller 2.66 first gear, which is completely unacceptable with the 2.77 rear currently in the car.

LT1/TA

My 94 formula had 3.42's and it was just to high,I went with a 4.10 set out of a 94 S10 and it was a great gear and the gas mileage was about the same.

My 88 has 4.56 gears and I love the way it drives and it still only turns 2100 rpm's at 70mph.

I dont think i would put 3.73's behind a t56,I think it would be to close to the 3.42's that came factory behind the T56's. That is why I wanted to hear from guys running 3.90's.I do think the 3.90's would be a good gear.

QwkTrip

iTrader: (22)

You've already had 4.10 gear so you know what that is like. 3.90 ratio is only 5% less so you probably won't even know the difference.

If you're going to select a gear ratio then you really need to consider torque applied by the tire to ground. I have 3.73 gears and it works well but my engine makes a lot of torque. If I put 4.56 gears in my car then it would become a spin fest because I could not harness the torque to ground.