What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

12 Bolt 4.10's

Grieby54

Grieby54

1/2 ton status
Joined
Jun 18, 2005
Posts
782
Reaction score
0
Location
Houston, TX
I have a 12 bolt with 3.08 gears it would appear. So now I need 4.10 gears to go in 'em. Do I need a new carrier? Are there different sized gears for a 12 bolt? Anybody have some 4.10's they can sell me for a 12 bolt. Thanks
 
3.73 and deeper is the carrier split. It seems like it's damn near impossible to find a 4 series open carrier.
 
So to go from my 3.08's to 4.10's... I'll have to get a new carrier too? Things just keep getting better. And on top of that... it's nearly impossible to find one that's not locked?!
 
Well, my K5 had 3.73s and a 10 bolt/12 bolt with a Gov-Lock. I probably opened up ten or eleven 12 bolts in the junkyard looking for a 4 series open carrier to weld up. I either found open carriered 2.76s/3.08s and I think one 3.42 or I found 3.73s and 4.10s with Gov-Locks.

I don't know, it might be an isolated case... I'm a pretty unlucky person.

I had a friend weld up my Gov-Lock and I broke it the first time I tried pulling someone out. I had another friend weld it back up and we'll see how it holds up. I'd still rather have an open carrier.
 
Grieby54 said:
Gov lock... is that just like a limited slip... or is that like a detroit?
Click to expand...

It's like a middle of the road turd...gov-locks are notorious for breaking. They are (I believe) a ratchet type locker. When the speed differential between the two wheels hits a certain point, it locks up. Kind of a pile, I recently had one grenade on the street.
 
8.875

It's probably bigger on the 4.10's, which is why you need the new carrier to begin with, otherwise the teeth on the gear will be too thin. (There's more teeth on the gear). Call their tech line, they'll know. :D
 
Since you're my hero who knows all LI... how much do you think it'll run me for a new carrier and 4.10's?
 
Got the front 4.09 gears used with new carrier... and 4.10's for the rear axel I thought I had... that's how I figured out it wasn't a 60... so just the rear... how's it looking LI?
 
4.09's vs. 4.10's

The slight difference in the gears front and rear will cause BIG problems if you run it in 4wd in anything other than mud or real loose ground. At any speed on even a firmly packed dirt road things will start to go "Boom" from the drivetrain being in constant tension. That's why they have to match front and rear with the same size tires.
 
I posted asking about this in the forum and people said that GM gave out front to rear ratios .01 off stock most of the time. And that it was a smaller difference than un-even tire wear...
 
A Little math

Here's one way of looking at it. (I am ASSUMING that when you wrote "4.09", that that was not a typo) A gear ratio is driveshaft speed in rpm's vs. wheel speed in rpm's. Assuming you have the same size tires all around, if the driveshaft spins 4.10 times, your front wheel with 4.09's will have spun .99 times, while your rear wheel will have spun once. Assuming a final drive ratio of 1:1 in your tranny, and an engine speed of 2,000 rpm, your front wheel would be almost 2 complete revolutions behind the rear ones in just ONE minute ("RPM"- Revolutions Per MINUTE"). In just 3 minutes of driving it would be almost 6 revolutions behind. You can see where this would put ALOT stress on drivetrain parts it was not designed to handle, and eventually it would just twist itself to pieces.
 
More math

Here's a simpler way to look at it.
Assuming the same 2,000 rpm and 1:1 final drive ratio, with 4.09's in front, your front wheels will turn 488.99 times, rears with 4.10's will turn 487.80. That's a 1.19 difference in wheel rpm per minute. After 10 minutes would be an 11.90 difference, and so on. Get it?
 
It is impossible to get matching gear ratios when you have different sized ring gears... unless you happen to get a ring gear that just so happens to be a multiple of the other ring gear.

Ratios are a measurement of the diameter of the ring gear to the diameter of the pinion gear. The easy way to compare sizes is to go by tooth count.

As mentioned before, it is often impossible to end up with matching gears if the ring gears are different sizes.

Since the dawn of time, vehicles have often had different gear ratios front and rear. As long as they're within 1% it doesn't matter. In fact, your favorite competitor (Ford) ran certain vehicles with a 1.6% difference. You shouldn't be running in 4wd on something that isn't slippery and can let the bind come out of the system anyway. AWD (such as the unlocked position of the NP203 or any other differentialed transfer case) it doesn't matter.

Maybe none of us should run lockers either... after all, if the tires happen to be a wee bit different in diameter we might done blowed up our axles. :haha:

Think about this for a minute. All of you people (and I'm willing to bet you yourself) that run the same air pressure in all four tires are actually subjecting your transfer case to more than 1% difference. The rolling circumference of the tires are quite a bit different. That's why smart people run varying air pressures front to rear. Well, that including a whole slew of things like tire wear, performance, and ride quality. Usually a 2-3psi difference.


Anyway, back to the original question. You need a different (4 series) carrier for 3.73, 4.10, 4.56... et cetera than for a 2.76, 3.08, 3.42 (3 series). The ring gear is 8.875". If you don't believe me, measure it.

You should buy a ring and pinion of decent quality (Yukon... $160. Richmond... $200) and buy a master install kit. You'll only need to buy one master install kit for that axle because chances are the next time you do the same axle type you'll have all the shims you need.
 
You must log in or register to reply here.

Latest Posts

Top Bottom