How To Install a 3rd Gen Off Road OR Axle On a 2nd Gen Tacoma (or non-OR 3rd Gen)

The weakness of the OEM rear differential under a 2nd Gen OR is well documented here on Tacomaworld. If you drive a Tacoma that is significantly heavier than curb weight (mine is 5500-6000 lbs., depending on the day) and utilize the 2nd Gen OEM rear locker for off-road driving, it is likely only a matter of time before you find out first-hand.

Meanwhile, the 3rd Gen rear axle assembly is improved in important ways. It uses a much more robust 8.75" ring gear, as opposed to the 8" gear in the 2nd Gen. The 3rd Gen also uses stronger 32 spline axles instead of the 30 spline axles found in the 2nd Gen. The differential locker mechanism is also completely redesigned to be more reliable, and is now inside the differential's bell housing, out of harm's way.





If you break your 2nd Gen rear differential on the trail like me, you will be left with the options of an expensive towing bill, or removing your rear driveshaft and ring gear on the trail, to limp home in front wheel drive. I live in Seattle but was 20 miles up a trail in Canada when I broke my rear gears, so only the latter option made sense. Much thanks to @bjohn041 and @stonylaroux for help tearing my truck apart and putting it back together.


This swap would have not been possible without Joshua Peace at ExperiMental Designs, maker of the Freedom Locker for 2nd and 3rd Gen Tacomas, working with me to develop a prototype wiring harness, to allow me to swap a 3rd Gen OR axle assembly into my 2nd Gen Tacoma. The Freedom Locker is an aftermarket wiring harness that allows users to operate their OEM rear lockers in 2WD and 4HI, so I knew he would likely have the knowledge to facilitate what I wanted to do. Josh came through for me in a big way, and he will now be offering a similar wiring harness for any other Tacoma owner who wants to follow suit.


Before you start this axle assembly swap, go ahead and remove your 4x4 switch. Unless you are already running the same final drive ratio in your front differential as what you will have in your new axle assembly, you will need to regear one (or both) of your differentials to achieve your desired final drive ratio and have your 3rd member gears match. In the meantime, you do NOT want to absentmindedly engage 4WD with mismatched differentials.


The swap of the 3rd Gen axle assembly itself is straightforward and completely compatible with the 2nd Gen Tacoma, so I won't cover that in detail. I sourced my used axle assembly on eBay, but I saw several others for sale on Car-Part.com. Be aware some vendors on Car-Part.com may require a core charge.

The hardest part of swapping the axle assembly is disconnecting your rear e-brake lines from the drum brakes on your current axle assembly, then reconnecting them to the brakes on the 3rd Gen axle assembly. TRQ has an excellent YouTube video showing how to service Tacoma drum brakes, which will get you to where you need to go. Much thanks here to @Shadowhunter for his knowledge of rear drum brakes and his assist for this swap. (It was more like I was assisting him.)

You will also need to bleed your rear brakes after swapping the axle assemblies, set your star adjusters in the new drum brakes, then adjust your e-brake. Again, there are YouTube videos that do a much better job of explaining this than I can do here.

So my subsequent posts on this thread will be dedicated to showing you how to install the wiring harness from ExperiMental Designs. Since my harness is a prototype, yours might look slightly different, but the install should be the same. I have no affiliation with ExperiMental Designs, but I wholly recommend their wiring harnesses from my own experience.

 

INSTALLING THE WIRING HARNESS, Part 1. This is perhaps only my second time installing a wiring harness on a vehicle, so any tips or suggestions on how it might be improved are welcome.


First, locate the raised area of the floor at the front right corner of the passenger seat. Note the plastic door sill cover next to it has been cut out here. The rear edge of that raised area is a good place for the wiring to run from under the plastic cover to under the carpet.


Next, remove the passenger side kick panel and pull up on the aforementioned door sill cover to expose the wiring channel. The door sill panel can be pulled straight upward, and the passenger side kick panel uses a small rubber stopper at the front of it which just pushes into place, but can be twisted out like unscrewing a screw. Then the kick panel pulls straight backward. You may want to start with removing the rear door sill panel first, but I don't think you have to. This is a good opportunity to vacuum this area out.




Next, lift the carpet under the passenger seat and locate the rubber floor plug under the passenger seat. Remove this plug.




Next, open the glove box and locate the bolt at the top center under the glove box latch. Remove this bolt – I believe it is 12mm – and remove the black plastic cover it holds in place. You can completely remove the glove box for more room to work, but it is not necessary.


Next, thread this end of the wiring harness from above the glove box down the passenger side. Pull it all the way through and thread it to the aforementioned location in the door sill wiring channel, where it will cross from there to under the carpet of the passenger seat. It will be covered by the kick panel and door sill cover when you put things back together.





Next drill a 1/4" or 3/18" hole in the plug, then cut a slit through the thick center of the plug. The reason to drill the hole first is it will let the plug sit more flat once the wiring harness is threaded through. Use your soft passenger side seat as a work surface for drilling the hole and cutting the slit.

Just kidding. Do not do that.


Thread the wiring harness through the plug, ONE TERMINAL AT A TIME, being careful not to lose the letter labels attached to each terminal. You don't want to get these terminals mixed up. Have scotch tape on hand to re-affix any of the labels that come off.


Thread the terminals through the access plug hole. They will come out under the truck just outboard of the frame rail. Pull the entire length of wire through, except what you will need for the wire to run its intended route from the door sill cover, under the carpet, and to the access plug hole.


Use silicone sealant to seal the slit around where the wire passes through the access plug. I suppose you could alternatively use a hot glue gun, which dries faster, but silicone sealant will be easier to work with if you need to make later adjustments. The silicone sealant will take a couple hours to set up, so move on to the next steps, and wait before placing it under the carpet and in its access hole.




Back to the glove box: Locate your truck's 4X4 module above the top right of the glove box, one which you will see two plugs aligned vertically. Unplug the LOWER plug, and patch in the appropriate plugs on the wiring harness. One plug on the wiring harness will plug into the lower socket on the 4X4 module, and the plug you just removed from the module will plug into the corresponding socket on the wiring harness.


On the left side of the glove box, find the bolt that holds the plastic dash to the metal support behind it. Remove this bolt and wedge the ground eye on the wiring harness between the plastic and the metal support. Replace the bolt.




Thread the switch plug end of the wiring harness down behind the glove box and behind the passenger side foot heater vent. You will see a tunnel below the head unit that will allow you to run this end underneath the head unit into the driver side foot well. Note, if you are installing your locker switch in a different location than I did, these steps will vary.


Take up extra slack on the switch end of the wiring harness by wrapping the wire around the legs of your brake or gas pedal.

Just kidding. DO NOT DO THAT.


Run that wire well clear of your feet and the brake and gas pedals. Pass it over the steering column.


The switch end of the wiring harness (obviously) plugs into the the locker switch. I installed my locker switch here, because it is next to my other traction controls. Removing the drawer/ fuse panel cover to the lower left of the steering wheel gave me lots of access to work. Once you have your switch installed, gently pull slack in the switch end of the wiring harness back to the glove box, and zip-tie the wire up under the dash (not shown) to be extra sure the wire will never interfere with your feet while driving.


Back at the glove box, coil and zip-tie any slack you have left in the switch end of the wiring harness. Tuck that, plus the control board for the wiring harness – the black box to the right – above the top panel of the glove box. Push that panel back into place, reinstall the 12mm bolt, and close your glove box. Time to crawl under your truck...

 

INSTALLING THE WIRING HARNESS, Part 2


Back under the truck, you will have some extra wire length when routing your terminals to your differential. Wrap them around the exhaust or the driveshaft to keep it from dragging.

Just kidding. Do NOT do that.


From the access plug under the the passenger seat, run your wire along the frame rail (not pictured), all the way back to the frame cross-member that holds the carrier bearing. Zip-tie as you go. At the frame cross-member, you will want the wire to cross the exhaust ABOVE the exhaust heat shield, and above the cross-member. A 10mm deep socket works best for removing one end of the heat shield, but a 10mm crescent wrench will do in a pinch.


Attach your wire to the cross-member above the carrier bearing, and keep working your way back, securing it with zip ties as you go.



Run your wire above the fuel tank, behind the fuel tank's heat shield. Here, use an adjustable crescent wrench or similar tool to roll the edge of the heat shield over, so the wire does not cross a sharp edge.


The wire will come out from over the back end of the fuel tank. Make sure you have sufficient length that it will not be pulled tight when your rear suspension is at full droop. Zip-tie the wire where it will not cross a sharp edge before it proceeds down to your differential.


Press the wire terminals into the included gray plugs, with the letter labels on the terminals corresponding to the labels on the sides of the gray plugs. The terminals will click into place.




You will see some white plastic fins protruding from the faces of the plugs. Press these downward until they are flush with the faces of the plugs. They will click into place.


Next, remove this shield on the top front of your differential's bell housing. There are two 12mm bolts.




Unplug the existing plugs under the shield that you just removed, and install the plugs from your new wiring harness in their place. Tuck the old plugs in next to them, and re-install the shield.




While you are there, if you plan to utilize aftermarket leaf packs, use your adjustable crescent wrench to bend the bracket on the top of the differential upward. Then disconnect the the axle's OEM wiring harness from the bracket above that. This will allow these lines enough slack to not be pulled taught during full droop of your rear suspension. ALWAYS TEST by jacking up the rear of your truck to full droop and examining every line for slack. DO NOT find out the hard way on the trail that you don't have enough slack somewhere.

Work your way back up to the cab. Cut all your zip ties; double check that your new wiring harness is secure and out of harm's way. Press the access plug under the passenger seat back into place. Reinstall your passenger side kick panel and plastic door sill covers.


Test your differential locker: The button should light up only when the differential lock is engaged. It will not often light up immediately when you press it, because you have to roll a few feet for the differential lock to engage. If it doesn't engage quickly, try straightening your steering wheel or turning your wheel slightly from side to side as you roll.

The process for turning off the differential locker is the same. The light will not turn off until the differential locker is disengaged.

Enjoy your new differential locker any time you want it – in 4LO, 4HI, or 2WD. It's probably not a good idea though to have it locked during a turn on dry pavement.

 

I believe the 3rd Gen uses an Electromagnetic locker.
So no more actuator failures too......NICE.

 

Happy I could help and even more glad it actually worked. I mean on paper it should have worked, but I still wasn’t 100% we could pull it off until the E-Brake cables fit. The axles have different splines so you can’t just pull them and stuff them in the 3rd gen housing without taking the brakes apart.

 

I finished posts #2 and #3 of this thread, showing how to install the wiring harness. Any feedback is welcome.

 

Cool thread! I've been on the hunt for a nice, low-mile 3rd gen factory 4.30 front diff for a cheap(er) re-gear but maybe I need to just grab the rear axle too.

To confirm, drive shaft lengths stayed the same with the swap?

Also, my 2nd gen DCLB didn't come equipped with a factory locker. Do you happen to know what else would be needed beyond a 3rd gen e-locker axle assembly and Josh's wiring/switch kit to have a functional, factory e-locker?

Thanks!

 

Dude excellent write-up! Thanks for posting!

 

I didn’t swap driveshafts. I took the truck to 80mph after the swap — no driveline vibrations.

I am running a carrier bearing drop kit and axle shims to account for my lift, but if you don’t have driveline vibes now, you shouldn’t have them after the swap.

Except for some brake fluid, and maybe some other shop supplies you probably already have, you don’t need anything else to make this work. My truck didn’t come from the factory with a differential locker either (although in the interim I had installed the 2nd Gen OR axle assembly).

 

To be clear, when I took measurements of the 3rd Gen axle assembly, I noticed that the bell housing for the differential was .25 inches shorter than on the 2nd Gen. Since our driveshafts telescope a whole lot more than that, I gambled that this would not make a difference, and it didn’t.

 

Thanks for the quick reply and info!

 

Kool!

Does it light up the locker LED on the dash when engaged?

And what are you gonna do when you eventually swap in a manual tcase and delete the 4WD ECU?

 

I don’t have a locker LED on the dash. I drive a TRD Sport. I’m not sure whether it would light the dash LED on a 2nd Gen OR: that’s a question for Josh at ExperiMental Designs. I think it would, but don’t quote me. I believe that’s the way his Freedom Locker works for both generations of OR’s.

No plans for a manual Tcase here, although I strongly suspect Josh already knows how to handle that too. I’m pretty sure the only thing this wiring harness is doing with my non-OR 4WD ECU is pulling power.

 

Every 6-lug 2nd gen (maybe even 5-loggers) has the locker LED in the dash cluster. The yellow/blue wire in the cluster harness needs ground to illuminate the locker indicator light.

 

Oh, good to know!

 

This is Bad Ass!!! Thanks for the write up. 3rd gen rear with lockers on a non-locker 2nd gen, bad ass!!!
Them to get the fiberglass fenders for a 3rd gen that pretty much mate up to a 2nd gen, and I'll have a new truck!!! TW; tha ks for putting me in Taco-Debt up to my..... Tacos!!! Mod & Rock on!!!

 

@essjay for when you break the rear diff

 

I'm on a SR5, so I already have an 8.75" diff. Installed an aftermarket locker when I regeared.

 

Sorry, you mean the so-called 8.4”. It’s actually still an 8” ring gear, but it is stronger than the ring gear in the 2nd Gen OR trucks.

8.75” diffs only come on 3rd Gen trucks, and only with manual transmissions or with factory differential lockers.

That said, you have the next best rear differential after the 8.75”. The so-called 8.4” is pretty strong.

 

They should have used carrier bearing trusses on the 8.75 too