Regearing --- help!

Hey guys! Im putting a 6inch lift on my truck with 37s and 20 rims. Im really confused on the whole regearing thing because I cant afford to drop 500$ on new gears once all of this stuff is on my truck. I have stock gears right now

$500? you need more then that for a re-gear.

What gears do you have?

NYCruiser said:

What gears do you have?

Click to expand...

I have stock gears right now

whitethunder said:

I have stock gears right now

Click to expand...

I think he means 3.21, 3.55, or 3.92

Oh lawd..

Is the lift already on the truck?

What size tires were on your truck from the factory ? 245/70/17, 265/70/17 or 275/60/20 ? There's a sticker on the inside of your drivers door that will tell you.

Then underneath your truck, on the driver's side rear axle tube, right near the shock mount there will be a white sticker with a bar code on it. You may need to wipe road grime off to see it. This will give you your axle ratio. I think they were 3.50 but I am not sure.

Remember, for a re-gear you'll need to change both the front and the rear gears.

In no way assuming you dont know, just trying to help you understand what 37's will do to your truck and the 'personality' of the truck unless you re-gear it.

I currently dont have my truck with me because its broken, but im fixing it this weekend so ill check then. I mean if i put the 37s on there it wont screw anything up will it?

It wont hurt anything really, I just want to try to help you truly know what youre getting into.

When the truck was built, the engine was designed to run at a certain RPM range for maximum power / efficiency. The camshaft (among other things) run at optimum power at say between 1500 and 4000 rpm. The engine makes the most horsepower vs. the fuel it consumes inorder to make it.

Stock, your tires were .. say 265/70/17.

265 / 25.4 = 10.43 The tire is 10.43 " wide
70 is the ratio of the tire meaning the percentage of the width. 10.43 * .70 = 7.30 This means from the ground to the bottom edge of the lip of the wheel is 7.30" tall
Now, there's two of those (top and bottom) so 7.30 * 2 + 17 = the diameter of your tire overall. 31.60 in overall diameter. So compare that to 37" on your new tires.

Now, take the two tires and put them side by side. Draw a chalk mark on the stock size and roll it one revolution. Do the same for the 37" tire.

Stock = 198.54 circumference 37" = 232.47


So .. say stock you have 3.50 gears and a 198.54in circumference tire. Put the 37" tires on and your gear ratio DROPS to 2.98

The tires will also be heavier.

The gear ratio is what you feel 'out of the hole' So your truck stock with 3.50 ratio gears for example. Put a 4.50 gear in it and it would feel extremely strong off the line but rev really high on the freeway. The higher that number, the higher the engine rpm but more power. Drag racers run big gears.

Going back to the engine power, put 37's on it without a gear change now your engine has to work even harder. It's more difficult to get the truck into it's effiency range (so it will use more fuel) .. simply because the tires turn slower per revolution. Gas mileage will drop significantly.

My suggestion would be if you want to go that big, really look at the gearing. IF not the truck will be really sluggish out of the hole. Red-light-to-red light driving will be painfully slower and the truck will feel like it doesnt have as much power.

You will feel it in the wallet too.

Hope this helps
Chad

You'll probably want to go with 4.56 gears. But to get that done you'll have to have both the front and rear diffs machined out. The whole gear swap would cost around $2-3k.

Might want to consider swapping the complete rear axle (both front and rear if you have a 4x4) with some used units from a salvage yards with the gearing you are seeking.

I can reduce the overall cost if you do it yourself, otherwise it depends on your mechanic's rate and the price of the salvage units.

Just a tought

Just for reference -

31.6" tall tire stock + 3.55 gears = 3.55:1 effective fear ratio
37" tall tire + 3.55 gears = 2.98:1 effective (right at 3.00:1)
37" tall tire + 4.10 gears = 3.50:1 effective

So, regearing to 4.10 would put the truck right about where it was stock with 37" tall tires on it. (Assuming 265/70/17 is the stock size)

4.56 would definitely help too but the RPM on the freeway will be a little higher. There will be a noticeable difference in off the line power too. It will bring those big ole meats up to speed quickly. (4 wheel burnouts too!)

Honestly man, if you can't re-gear I wouldnt do it at all. Just me. Here is a calculator I use for this type of thing. http://www.4lo.com/calc/geartire.php

When recalculating, remember that you need to go higher (numerically higher = lower gear ratio) than calculators give you to compensate for the added weight. Gearing ratios get you the RPM, but to have the power to accelerate you will need more power than before. So you want to be a little higher in the RPMs.

Yep .. I agree.

Is there an option between 4.10 and 4.56 ? That might be the sweet spot. I dont think I'd go over 4.56 though