I'm new to gears and I was wondering if anyone has ever installed 4:10 gears with a T-5 trans. If so, how much of a difference did it make? Also, would the car still be able to be driven on the highway? What kind of rpms (max) in each gear would I be looking at? I know that 4:10's might be a little drastic but i'm looking for new gears for my rearend. I'm looking for good acceleration with not a lot of loss on top end. Help and opinion would be awesome.

 

What gears do you have now?
Yes you will lose top end because that ratio will limit how fast you can go before you max out the rpms. The car will accellerate rapidly and top out sooner. At 70 mph on the freeway I would guess you would be cruising at 3200 rpms.
Remember you also have to change the speedo gears in the trans so your speedometer will read correctly.

 

I ran 4:10's for years but I also had 275/60/15 tires in the rear. No problems on the highway.

Can't remember the rpm's at highway speeds.

 

I used to want 4.10's too, but after I got my TA which has the T5 and 3.73, I gotta say I am glad I didnt, even with just 3.73's my top end sucks bad. Even in overdrive at 80mph it turnin over 3000 rpm. And at that rate your absolute max speed based on not exceeding redline would be about 130mph. And thats with a 3.73, so add the 4.11 and I think you would be talking max speed of about 110mph. to 115mph in 5th gear and thats at 5000 rpm redline which isnt advisable at all. Now keeping in mind that your not supposed to use overdrive when under full throttle, if you stayed in 4th gear, your gonna be lucky if you even can hit 100mph.

I think you would be better off going with the 3.73's cause top end isnt all you need to worry about, you also gotta remember that the more gear out back means the lower ratio your tranny gears become. With the 3.73's my 1st gear is getting near useless for anything but burning tire. I can start out in 2nd without any problem. If you go with 4.11's you will likely lose your 1st gear because it will be such a high ratio it will be useless. Kinda like the granny gear in the old trucks.

 

gearing needs to be chosen based on the engine's powerband. 4.10's would be way too much for a factory engined car. In fact, you would probably slow down even in the 1/4, as the engine would be "out of breath". 3.73's at the most, 3.42's are often a great choice for a torquey street car on 26" tires(approx factory size).

There is a gear calculator on this site as well as many drivetrain sites that will give you rpm vs speed vs gearing.

 

I ran 4:10's with a T5 behind a destroked 400 with a 3.25" crank. It did fine on the freeway with the stock 16" wheels and tires....about 2500 rpm's...but first gear was worthless. Would have been much happier with 3:73's or even 3:45's for street driving. Unless you ran slicks on the drag strip, 4:10's are very difficult to gain traction. I had the full Spohn treatment of heim-jointed LCA's, Torque Arm/Crossmember, Lowered LCA mounts and the car was too easy to blow through the traction control and smoke the tires. I would think 4:10's would be happier behind an automatic.

 

Thanks for the advice. What brand would be the best though?

 

Can't go wrong with Richmond but if your only going to do street driving and your looking for a little extra acceleration, I'd go with the factory 3:42's as Shagwell suggested. You can pick up a nice set cheap on the "Engine/Drivetrain Parts for Sale" section and with a fresh posi, you'd be happy with the performance behind your 305.

There is a point of diminishing returns with these 10 bolt rear ends. If you're going to run slicks at the drag strip or your eventually going to build a monster motor....or both, it's better to start looking for a 9" Ford, 12 bolt Chevy or at the very least a 9 Bolt GM. I would sink too much money into the 10 bolt if that's in your plan. It wasn't designed to take the abuses of racing or extreme performance motors. Even modified, it has it's limits.

 

I have Yukon 4.10 gears in my 10 bolt. They have been in there for several years now with no problems. Also, they are as quiet as any stock gears.

As for the T5 and 4.10's, they are great together. Remember that alot of the T5's have a .63 overdrive. 2500 rpm at 65 -70 mph. I have seen 18 - 20 mpg in my car with the 4.10's on the freeway, which is pretty good for a mechanical secondary Demon carb.

I also installed 3.73's and did the auto - 5 spd swap on my wife's 87 Firebird. Stock LG4 and the combination of gears and transmission really woke it up. She has seen 25 mpg out of it.

 

I can belive that, my 90 L03 with 5 speed got over 30mpg with 3.08 gears, so 25 is believable with 3.73's, but certainly not while drive 80 down the highway...lol. I was going 50 to 60 when I got 33mpg.