How to weld “Lock” Rear Differential Vitara Tracker


Traction offroad is the name of this game and nothing adds more traction than differential lockers. Today we go through a how-to add a ‘welded’ rear locker to any rig that is technically ‘free’ if you are willing to put in the sweat equity.

So far I am still at less than $2k total with my Suzuki Vitara build ‘PJ’. With this project, it is my aim to spend as little money as possible and spend only where it makes a difference. The next step to increase the offroad traction. The best and cheapest way to do that is to weld up solid the spider gears in the rear differential.

I start at the basics so feel free to skip ahead if you already know some of this material.

What is a differential?

A differential is a component inside of the axle of vehicles that allows one tire to turn faster than the other tire during turns. There are generally one or two axles in a vehicle depending on if it is 2wd or 4wd. In our case here the Vitara has two, one in the front and one in the rear. Within the differential there is a ring gear that transfers rotating force into a carrier that houses the ‘spiders’ and side gears that allow the tires to spin at different speeds.

Basic types of differentials

  1. ‘Open’ differentials send all power to the tire with the least amount of traction.
  2. ‘Limited Slip’ differentials use clutch packs or worm gears to transfer SOME of the power to the tire with more traction
  3. ‘Locked’ differentials send all power to both tires. There are generally two types of locked differentials: ‘automatic’ which have a racheting mechanism for disengaging when cornering under low/no throttle and ‘Selectable’ which are engaged via air/electronic/cable actuators
  4. ‘Welded’ differentials are really the same as ‘locked’ but they never unlock because you literally weld the ‘open’ differential together so both tires will always spin. The downside here is that there will be additional tire wear and some hopping/chirping of tires during sharp turns on pavement.

Differences in brands

Welding the gears in a rear differential varies in difficulty depending on the vehicle it is being done on. This isn’t because the actual weld itself is harder, it is more of a problem of access. In a typical American vehicle with Dana 35, Dana 60/70, Ford 8.8, Ford Sterling, AAM axles you can just pop the cover and can usually see the spider gears. I have even welded the spiders on some of them without even taking anything apart. On the imports with drop out 3rd members it is a different story though.

Since the Suzuki Vitara/Trackers have drop out 3rd members in the rear axle, there is no cover to remove to get access to the gears. The rear axleshafts and driveshaft must be removed then differential un-bolted and removed from the axle housing. To get to that point we start with removing the wheels and brakes.

Disclaimer

WARNING, this project is not for the faint of heart or automotively challenged. However if you have a decent set of tools along with a few specialty tools and a lot of patience (or knowledgeable friends) anybody can do it. Also, this is meant to be a guide and is not exhaustive, some aspects of this project may have to be researched further on your part to cover knowledge gaps.

If in doubt there are always alternative options. Maybe you could remove the differential pumpkin from the housing yourself and drop just the pumpkin off at a differential shop to add a mini spool or automatic locker and re-set up the gears. You would save money by them not having to also disassemble or reassemble the axle itself.

How to weld "Lock" Rear Differential Vitara Tracker
Start by properly jacking up the vehicle and putting jack stands under the frame rails.
How to weld "Lock" Rear Differential Vitara Tracker
Getting the rear drums off proved to be a challenge. I ended up using a drill mounted wire brush to clean the rust off the ridge around the hub without damaging the studs.
How to weld "Lock" Rear Differential Vitara Tracker
There are two M8 x 1.25 (thread pitch) threaded holes in each drum. These are used for removing the drums. I tried to use class 8.8 bolts (grade 5) and stripped them out, I ended up having to go buy two M8 x 40mm class 10.9 (grade 8) bolts which ended up being strong enough to push the drums off. Alternate from side to side doing approx 1 turn at a time on each bolt so the drum doesn’t get caught at an angle.

TIP: Before taking apart any complicated device, be sure to take lots of pictures! You can get yourself in a pickle if you don’t remember how something goes back together. Digital pics are free and you can always delete them later!

How to weld "Lock" Rear Differential Vitara Tracker
Pics of the shoes and springs before disassembling so I could remember how to reassemble them.
How to weld "Lock" Rear Differential Vitara Tracker
How to weld "Lock" Rear Differential Vitara Tracker
Next step is to remove the 4 nuts on the back side of the drum backing plate that hold the brakes and axle in.
How to weld "Lock" Rear Differential Vitara Tracker
I didn’t take a picture of it but to get the axle shaft out takes some uumph. A slide hammer would have been optimal but I don’t have one. I ended up taking a 4x4x20″ board and placing it on the back side of the wheel mounting surface at an angle from the rear of the vehicle and giving it some solid whacks with a sledge until it popped out.
How to weld "Lock" Rear Differential Vitara Tracker
The part that needs removed is the axle shaft itself, NOT the drum backing plate that has the wheel cylinders and hydraulic lines which would need removed if you wanted to take it off. The backing plate can stay just where it is for this project.

Slide the axle shafts out ~4-6″ or remove them completely before starting to remove the differential pumpkin. Then drain the differential using the 3/8″ drive drain plug on the bottom of the housing.

How to weld "Lock" Rear Differential Vitara Tracker
Next step is to remove the driveshaft and hold it up and out of the way with a bungee or ratchet strap. Remove the differential axle housing nuts and remove the differential from the housing.

TIP: If you can’t get the differential to peel off of the housing due to the RTV (sealant), you can put a floor jack near the pinion end of the differential and apply light pressure until the seal is broken (don’t go crazy with it). You should then be able to remove the differential by hand.

How to weld "Lock" Rear Differential Vitara Tracker
Remove the differential from the axle housing. These are not that heavy (maybe 50lbs??) but grab a friend or transmission jack if you need help.
How to weld "Lock" Rear Differential Vitara Tracker
It is good practice in automotive work to both mark parts and disassemble them strategically so they go back together the same way they came apart. For this differential I took a center punch and made two dots on the right hand side carrier bearing cap and and side adjuster and one dot on the left hand side. I also counted and recorded on a sheet of paper the number of turns to remove each side bearing adjuster to use as a starting point when reassembling.
How to weld "Lock" Rear Differential Vitara Tracker
Here you can see I have a clean rag on the work bench where I laid the parts I removed out on the sides that they came from. This reduces confusion and chances for mistakes later.
How to weld "Lock" Rear Differential Vitara Tracker
Here is the differential carrier removed from the housing.
How to weld "Lock" Rear Differential Vitara Tracker
To get to the spider gears the carrier end cap was removed.
How to weld "Lock" Rear Differential Vitara Tracker
Here you can see that on this differential design the ring gear holds the spider gear cross shafts. Therefore in order to get the spider gears out we need to remove the ring gear.

Here is the part where I will tell you it is a lot easier to just pay the $150 or whatever it costs for a mini-spool. If you were going to use a mini-spool you could just replace the spiders with it and reassemble. However I am a glutton for punishment so continue reading to see how I welded the spiders up and reassembled (free! but also a lot more work).

How to weld "Lock" Rear Differential Vitara Tracker
Here are the side and spider gears that allow one tire to spin faster than the other when going around turns. We want them to stop doing such a good job so we can get more traction offroad.
How to weld "Lock" Rear Differential Vitara Tracker
When Disassembling, be sure not to lose these little guys. Each spider has a conical thrust washer behind it that helps keep everything lined up. The side gears also have specific thickness washers behind them so make sure to keep track of which washers came off of what side.
How to weld "Lock" Rear Differential Vitara Tracker
Disassemble and thoroughly clean the spiders, cross shafts, side gears, and housing. We don’t want any contamination when trying to weld it.

Safety warning – I used nitrile gloves, isopropyl alcohol, a rag, and 5 gal bucket to clean the differential parts which worked well. PLEASE be careful when selecting a cleaning agent. Some (most?) chemical residues are hazardous to your health when welding the parts after cleaning such as chlorinated brake cleaner. See this article for more info: Safety Alert!

How to weld "Lock" Rear Differential Vitara Tracker
Once everything was clean and reassembled (minus the side cap) I tossed the diff in the oven at 350 for a while to pre-heat the parts so I could get a better weld.

Due to the unique design of this differential case, I didn’t actually weld the spider gears (the 4 small cone shaped gears). What I ended up welding was the side gears to the carrier housing (the splined ones that the axle shaft goes into). The spider gears and thrust washers were in there when I reassembled it which helps to line everything up, they just didn’t directly get welded.

How to weld "Lock" Rear Differential Vitara Tracker
There are 4 windows on one side of the housing where I was able to just barely fit my MIG gun and get some weld on. I covered the ring gear mounting surface with heavy duty foil to keep weld spatter off.
How to weld "Lock" Rear Differential Vitara Tracker
Probably overkill but I couldn’t help myself. I welded all the way around the side gear. Remember, there is a cap that needs to go on this part so keep your weld smallish or at least out of the way of reassembling. Try to keep the weld spatter to a minimum
How to weld "Lock" Rear Differential Vitara Tracker
Gertrude giving me the ‘dad you are going to get us in trouble’ look.
After welding, I put the diff back in the oven that was off but still warm so the parts could cool slowly/uniformly (reducing risk for cracks in the welds).
How to weld "Lock" Rear Differential Vitara Tracker
Here is the diff after cooling and cleaning up with the drill mounted wire brush. I also had to clean up the mounting surface a bit to get the end cap back on.

Challenges

When putting the side cap back on the carrier it was tight partially because it is a machined fit and partially because there was likely some slight warpage or weld spatter I missed. So to get the cap to shrink up I put it in the freezer for a bit (the carrier was still warm). I took the cap out of the freezer and put it in the diff but got it cocked in there before getting it all the way down. By the time I ran across the shop for the hammer it was too late and the two had become one. I couldn’t get the end cap back off so I had to put it in the press and send it the rest of the way home. Luckily I had aligned the bolt holes when I started putting on the end cap. I partially threaded a couple bolts in to keep the holes lined up in the press.

A guy that owned a shop that I used to buy metal from a long time ago once said “Any tradesman can fix his mistakes” which stuck with me ever since.

How to weld "Lock" Rear Differential Vitara Tracker
With a good bit of pressure in the press, the end cap seated itself and I was good to continue on.

Torque Specs

The below differential torque specs were provided by ‘skyhiranger’ at this link: https://bbs.zuwharrie.com/content?topic=96669.0

From a 92 FSM (Field Service Manual, all in ft-lbs, except as noted)…..
diff oil filler plug…25.5-36
diff oil drain plug…13.5-18
prop shaft flange bolts…36.5-43
bevel gear bolts…65.5-72
bearing cap bolts…51-72
lock plate bolts…7-10
diff carrier nuts…36.5-43
upper arm bolts…29-43
rear wheel speed sensor bolt…13.5-20
pinion bearing preload…7.8-14.7 in-lbs
pinion starting torque…4-7.5
bevel gear backlash…   .005-.007

Reassembly

How to weld "Lock" Rear Differential Vitara Tracker
Next I torqued the end cap bolts alternating from side to side (use red locktite on these critical bolts when reassembling).
How to weld "Lock" Rear Differential Vitara Tracker
Reinstalled the ring gear with red locktite. Be sure to properly torque the ring gear alternating side to side so as not to warp it.
How to weld "Lock" Rear Differential Vitara Tracker
Next drop the carrier back in the housing and hand tighten the carrier bearing caps.
How to weld "Lock" Rear Differential Vitara Tracker
Then thread in the side adjusters by hand using the number of revolutions you counted when disassembling. I didn’t have correct spanner wrench, but my pliers seemed to work pretty well. These adjusters are for adjusting and setting preload, you shouldn’t have to crank on them crazy hard.
How to weld "Lock" Rear Differential Vitara Tracker
Since we didn’t mess with the pinion, there are two measurements that need reset. The backlash and bearing preload. Backlash is measured using a dial indicator and magnetic base. The indicator is placed on a tooth of the ring gear then the carrier is rocked back and forth while the pinion is held still. The reading here should be .004 to .006.

Once everything measures out right, we reverse all of the initial disassembly steps and put it all back together. Use RTV on the sealing surface and put the differential back into the axle housing, reinsert axle shafts, reassemble brakes, bolt in driveshaft, etc.

How to weld "Lock" Rear Differential Vitara Tracker
After a couple hours of reassembling Voila!

Below is a video from Kansas Rocks after completing the rear differential locker. I will tell you straight up that this little truck with 29″ all terrains went all kinds of places it probably shouldn’t have and kept up with a bunch of Jeeps with much larger tires. The biggest hangup was ground clearance which will be addressed eventually.

Again, this project is not for the faint of heart or automotively challenged. However if you have a decent set of tools along with a few specialty tools and a lot of patience anybody can do it. If in doubt there are always alternative options like listed at the beginning of this article.

Hope this helps. I tried to take lots of pictures to take the mystery out of this job however my guide is not exhaustive and you will likely have to do additional research on specific parts to fill any knowledge gaps.

Now YOU, go out and work on something! Then go rock crawling, drag racing, mud bogging, or whatever sport it is you are reading this for.

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