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Topics - Sparky

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Mitsubishi Related / How to swap ADD 3.15 gears! W/ Pictures
« on: November 11, 2017, 11:29:49 PM »
Let's be honest. The stock gearing for the Montero is pathetic. It'll do if you never have more than a steep incline or a slight obstacle, while rolling on 33s. However, if you roll on 35s and have a need to crawl, these 3.15:1 gears should do the trick.

If you want to know why I chose these gears, I will open a build thread in the future and answer the question there.

This how-to will assume you know how to remove the transfer case (t-case)  and I will begin there.

Tools you'll need:
A couple of flat head screw drivers
12mm, 14mm sockets
Torx bits
3/8 extension
brass hammer (rubber mallet would work)
Snap ring pliers
Angle Grinder
Magnetic retrieval telescoping pen
Crescent wrench
A punch set
Channel locks
Bearing press and removal tool
white grease
gear oil

Optional Equipment:
A 5 gallon bucket
Paint pen
1 cuss pillow

It's a short list, I know. This really isn't that hard. I will write about what to do and then post a picture that correlates with the directions. There is not a picture for every single wrench turn. I'm sure you understand.

Ok, so your gears arrived and your transfer case is out of the Montego. Its a heavy sumabich!

I found that even after draining the oil there is still plenty left over. By standing it upright in the 5 gallon bucket, not only does the remaining oil drain, it is contained, and the bucket works as a nearly perfect t-case holder.

After wrangling this tame case into the bucket, identify the four bolts you need to unscrew from the lid. (I don't know if it is called the lid, but I am going to call it that.) Three of the bolts will bright and shiny, but the fourth one is going to black and dirty.

Utilizing your brass hammer, a couple of flat head and your pryer, you should be able to separate the lid from the body. Hammer evenly around the lid. It doesn't need much force, slow and steady.

Set that piece to the side. Note that one of the gears is held under the lid by a metal bracket and some torx bolts. (a picture is at the bottom) You can remove that gear, press the center plug out, place it inside the new gear, press it into place, and put the new gear from the kit into position on the lid. A little sealant paint wouldn't hurt. 1 gear down and 2 more to go.

Note: there are a couple of bearings that sit inside the gears on the main shaft; they are made up of several needle bearings held together in a cylinder. These needle bearings can fall out so handle them carefully. You will have to keep these. I coated mine in white grease and that should keep them in place. If you mess them up, a rebuild kit for these t-cases is NOT cheap. Break them and you should scream into that cuss pillow, or at your neighbor.

Remove the 4 bolts that hold your shifting lever into place and the 8 bolts that hold the cover to your shift forks. this will open the t-case up so that you can take the old gears out.

Before removing the gears inside the body, you must remove the shift fork. Now that the cover to the shift forks is off, there is a single cotter pin that holds the shift fork into place. Grab the punch set, brass hammer and gently knock it out. It comes out nice a smooth. The picture below shows the cotter pin already removed.

Your shift fork should move independently from the shift rail. This next picture shows the different plug and switches that need to be removed in order to push the rail into the t-case (towards the rear of the vehicle)  I removed the t-case from the bucket and placed it onto level ground. With the aid of my magical crescent wrench I removed the solenoids/switches. Don't forget to grab the ball bearings out with the magnetic retrieval tool. There is a ball that comes out the plug (unused switch port) . Not sure if you need to keep the spring and ball since it does apparently nothing but I didn't. (weight savings :)

Take your 3/8 extension and the brass hammer and tap that rail towards the rear of the case until the shift fork comes free. Set the shifting collar to the side along, with the shifting fork. NOTE: The shifting collar should be taken out and put back in facing the same direction. The shift fork that has been removed is the shift fork that needs some grinding.

Grab the snap ring pliers and your flathead screwdrivers. Take off this retaining ring.

Next, remove the two gears. The set on the main spline and the reduction gear. (This is the gear that is not attached to the main spline.) I recommend that you carefully remove the bearings from the reduction gear and reuse them with the new set. You should do that now. The smaller bearing on the reduction gear is a tricky retaining ring. The bearing does separate from itself very easily. Not to worry, with some serious grinding on the old gear, you can cut away enough that your bearing puller will be able to grab hold. I purchased a cheap puller and ground the shit out of it so that it would fit. LOTS OF GRINDING in order to use that stock bearing. I highly recommend you use it.

When I reassembled the bearings onto the new gear, the original retaining ring was giving me some grief. I think the gear was out of specs by a couple hundredths because it was not allowing the snap ring to seat properly. You may not have this problem. What I did was to grab the washer and grind it down on only one side until the retaining clip was nice and snug but still able to fully seat into the groove. Here is a picture before I switched the bearings. The retaining clip sits on top of the washer, holding the bearing into place.

NOW this is the part that most people probably fear... The grinding. Grinding is awesome. Especially when its on your lady friend. Am I the only person who remembers 8th grade? And unlike grinding on 8th graders, when you grind on the t-case, no one is going call you a pervert.

There are TWO places you need to grind. Shift fork and inside the t-case. The case is aluminum and it can be done with a dremel. I used my 2" angle grinder. Here is the where you need to grind on the case. The picture shows the cotter pin, circled in blue, and the two locations that need to grinding therapy, circled in green.

With my paint pen I made a mark of where the center line was on and started cutting. Grab a shop rag to cover up the parts of the case you don't want aluminum shavings on.

All done? It should look like this.

To test fit for clearance, just grab the largest gear and set it on. It should spin nice and quiet like. If it does, that means first part of the grinding has been a great success. Now grab that shift fork. There are two ways to understand where to grind. Read this. or just put the big wheel in, put the shift fork in and spin. You will hear the clunking sound as the gears smack the inner 'corner' of the fork. Grind that inner corner down and be a little generous. THINK 90 DEGREE.
This picture shows the results of your work. You can see how the light highlights the 90 degree grind you have to do. It isn't much but you might have to grind and test fit a couple of times.

Let's recap what you should have done.
Removed old gears
Changed bearings onto new gears.
Ground down the nub inside the case and inside corner of the shift fork

TO ME, this is the part I wish I had known. You need to put both gears into the case at the same time. The new gears came with a bearing that was slightly out of specs for my case and it was a headache. I hope it doesn't happen to you but I wish I had my cuss pillow. (you knew I would get one more reference in)

Put the case back into your bucket and stand it up.

When you put the gears in, EVERYTHING needs to be include, except for the shift fork. You can slide that in after the fact without any problems. Some slight rotating of the gears will help them drop into place. I applied a couple of taps with the brass hammer to seat the reduction gears.

Put the shift fork back in, align the rail and insert the cotter pin. Set the case level onto the floor and put the plug and two switches back into their locations with the appropriate ball bearings.

Remember that lid? pepperidge farms remembers. Stand the case back up.

Put some RTV around the top of the case. As you put the lid on, keep in mind that the gear that is underneath needs to be rotated until it clears the top of the reduction gears. Here is a reference picture.

Now that the lid is on, torque down those four bolts and set the transfer case onto the floor again. Put the cover back on, tighten the 8 bolts and then put the shifter back in along with the 4 bolts.

Run it through the gears. At this point it is ready to go back into the montero. DON'T FORGET to fill the oil back up. I used SAE90; after the first couple hundred miles, I plan on flushing it out and going with some synthetic oil.

In case your still reading, this should put your crawl ratio at 43.22:1 According to google, this is a good crawl ratio.

If I missed anything or need corrections let me know. I didn't proof read this.

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