1985 4Runner, 4.30 stock gearing, 33x10.5 tires, automatic, 22re

Hello everyone and Happy New Year! For over 20 years I have been plagued with leaking front axles seals and I have temporarily fixed this by rebuilding the front axles with Marlin Eco seals. But this is only a bandaid fix as the birfield axles have grooves worn into them. I want to fix the issue permanently and install new axles. While I am in there, I would also like to re-gear but a lot of this is foreign to me and hope that someone can review my plans (below) and tell me how crazy I am.

1) Install new Ultimate 30 spline Birfields from RCV Performance. I was informed that this comes with a new 30 spline inner hub gear but I have no idea what this part replaces.
2) Install Nitro 5.29 gears front and back. I really don't know what all this entails and will probably bring my third members into a shop to have this done correctly and shimmed unless this truly is a cut and dry procedure.
3) Install Marlin's Axle seal kit and eco seals. This will also replace bearings and felt backing seals (I already have their beefed up brass backing plates)
4) Install factory Toyota rear axle seals since I believe I have to pull the rear axles in order to disconnect the third member and re-gear

I have some further questions on this. I was thinking of installing an ARB air locker in the rear (RD132) but will this cause issues with the new 5.29 gears? I assume the locker does not replace the gears, correct (I would still need both the locker and gears in the rear)?. I do moderate 4wheeling and never had any issues getting stuck in this vehicle--so maybe I don't need the added complexity of the locker. Also, the new birfields are 30 spline and the Nitro gears are 29 spline. I assume I need to find either 30 spline gears or 29 spline birfields, correct? In other words, I cannot install 30 spline axles into 29 spline gears or is that what the inner gear hub helps with?

Thanks for any information and sorry to sound kind of newbie on this. I have experience doing some of this work considering I have replaced axle seals at least 5 times between my 4runner and and my 80 series but I just don't have a lot of knowledge regarding third members and the workings of the differentials aside from regular drain/refills.

Thanks,
JARED

 

The hub gear is a 4340 upgrade for your manual locking hubs stock inner gear. If the inner hub gear breaks it can damage the splines on the birf.

Dont attempt to setup gears if you dont know what your doing. The setup will make or break your diff. You might even save a couple bucks just buying a complete diff from marlin or another reputable shop.

Having an ARB installed with your new gears will not cause any problems. It will replace your stock carrier/spider gears and make you diff stronger.

The pinion is what's 29 spline. You will need a 29 spline triple drilled flange. You can get these from nitro or marlin. You should have new flanges installed when rebuilding the diff anyway, just get 29 spline instead of 27. The old originals likely have a groove from the pinion seal and will leak.

If you want a nice gasket to keep the new diffs from leaking, Checkout lubelocker gaskets.

 

Thanks Toyoda Addict. You've provided a lot of helpful information and it sounds like I am on the right track but I probably am way over my head when it comes to the gearing setup. I'll look into finding a reputable shop to help with that as I would like to keep my original diff and buying a complete replacement isn't an option yet.

Thanks,
JARED