So I've always wanted a locking rear diff, well my current diff is making a growl and after checking it out, seems like a bearing in the 3rd is going. I came across a complete locking axle out of a limited and front too, for a very fair price. I was planning on just doing seals and bearings, then swapping axles and in the future swap the front diffs, I don't use 4wd that often. I'm assuming (I have to verify both gear sets) I have 4:10 in my current setup and I'm also assuming 4:30 in the locking axle. I will verify All gears prior to any work, so my questions are; what would I gain by going from 4:10-4:30 front and rear, how bad could I hurt my rig having 4:10 front & 4:30 rear(only in 4wd) and should just look to sell/trade my 4:30 3rd for a 4:10? I've read up on this, but not clear. I know front and rear have to be within 5% of one another, so I'm not trying to do that( if I did, it would be just for a bit). I've near messed with gears ever, so it's not my preference to swap 3rds, but I feel I could if needed. I'm just looking for helpful perspective as I plan my next major maintainence/mod project. Again I will verify gears before work begins, but generally safe to assume 4:10 non locking 5spd, and 4:30 for locking auto. Also any helpful first hand dos and donts are always welcome, thanks. Keith

You will cause drivetrain bind up if you use 4x4 and the gears dont match.

Just swap them both in and your golden.

Its a bit higher gear ratio so will not cause any issues.

I went from 3.90 to 4.10 and didn't really notice any difference. I would suspect going from 3.90 to 4.30 would be more of a difference but the ratios we are talking its very minimal if any difference. I had heard you have to be within 2% with the gear ratios but then gain I was told that verbally when I wanted to put a 4.10 rear in when I had 3.90 fronts and didn't want to risk it.

What you gain would be negligible, less than 5% reduction in final drive ration. If you went a size larger on your tires, it might be enough to compensate. Not a big deal at all.
As for running two different ratios, off road you could probably get away with it, loose dirt is very forgiving. That said, I WOULD NEVER do it on my truck. Especially if you were going fast it could damage your transfer case. At 2500 RPM in 3rd gear 1:1, the difference between the front driveshaft speed and the rear would be about 125 RPM, that is a lot since they are coupled. If you don't have slippage on one or both of the axles, something will die.


Edit, actually it would most likely be a U-joint that would die.

You could drive in 4WD with different gear ratios for a few feet in an emergency. That's all I'd do. (I have done this before and it didn't cause a problem).

Let me be clear. I wouldn't run her in 4wd with mismatched ratios, just from house to buddy's shop/lift for the front swap. Really trying to gauge which option to be better for me. Given front diff is a pita to mess with, probably best to find a 4:10 3rd to swap into my axle? Or just swap both and go to 4:30? I know not much gain, but would I loose any top end or other effects the 5pd gearing/drivability?

4.3/4.1 = 1.04878...

Your RPMs in any given gear will be 5% higher with 4.3 gears vs. 4.1 gears. So, what used to be 2000 RPM will be 2100 RPM.

Unless you top out 5th, you won't lose any top end. You might loose a tiny bit on MPG, but you gain 5% in torque to the ground in every gear. Your speedo will still be accurate, since the speedometer is driven from the ABS sensors.

As others have said, make sure your front and rear gears match if you use 4WD. You can drive around in 2WD with mismatched gears without causing any problems.

-Charlie

No problem at all. As long as you don't engage the 4wd it is driving as usual.

Now I've done a couple of front diffs and they really aren't that bad. The trick is the rotation as you lift it out. It's easier with the truck on the ground honestly.

As far as the driving with the 5spd it really doesn't make that much difference but it is easily countered by a set of the 235/85 r16 tires which sets it right back into stock range. I have a 5spd and this is what I did. Mpg drops of course gearing up and you might be able to tell the difference a little but it's nothing to write home about. You aren't throwing 4.88 gears in.

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This is how mine is at the moment. I put the locking 4.3 in yesterday and got the locker working but I will not be able to change out the front 4.1 for a week. No big deal just don't put it in 4wd and if you are really stuck just engage the locker! I wanted the 4.3 to make up the difference between the 275/70 I had on it before and the 285/75 I have on it now. After driving it I can tell the difference in gearing and every little bit helps on the roads I drive on

Swap both no problems

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I thought the speedometer was driven by the speed sensor that's located at the rear end of the transfer case.

Only on non-ABS 4Runners. Almost everybody on here has ABS and it runs off the ABS computer in that case.

There is a cover on the speedo sensor hole on the back of the t-case which can be retrofitted with the sensor if the ABS system is deleted, etc...

-Charlie

Yep like this guy. I don't have an abs system lol

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If you are swapping a locker into a vehicle but afraid of removing the front diff to make things easier on yourself, then you might want to re-think the whole process. You will still need to build/buy a harness, switch and take the wire loom from the e-locker connector up to the gas tank region where it connects. I have a NON-ABS vehicle so I just made my own harness the whole length forward of the connector @ the gas tank/under drivers rear seat.

I just did the 4:10 to 4:30 swap on my 5-speed 3rz 4runner. It's noticeable with my 33's and armor. Nothing crazy, but it gives it a little extra kick in the ass.

Front diff is easy. As mentioned, you kinda have to lift it up and roll it out. There is a locating stud on the back of it that has to come up and out of the frame, then you "roll" the differential forward and match the oil pan shape. You can also get the flange caught on the bellhousing too which will piss you off. I have done it 3 times now, this last time I removed the mounting arms off the front diff (3 bolts per side, 21mm if I remember correctly) and this made it much easier to manipulate it around and get things in-line.

Thanks y'all, I'm back to my plan to just swap both. I'm pre wired and I've picked up everything but the ecu. I'll get that soon and those bearings/seals. Then paint and install.