Before You Start
There are basically two intimidating parts to a transmission swap, clutch change, or similar.

1) Trying to find all the right bolts to undo, and 2) Having to heft around a piece of equipment that weighs more than you do.

Once you have psychologically prepared yourself for these eventualities, you're ready to delve into it. Prepare for an adventure. This will take twice as long as your initial estimate.

For my own transmission swap, things were further complicated by the fact that it was a prototype setup. Nobody had done this before that I was aware of, so certain things had to be dealt with on the fly, as it were. What follows is a synopsis of my own experience at putting in a Marlin Crawler dual t-case setup in my Isuzu Amigo.

Here's what I had to work with. You'll need similar items:

• A late model Toyota five speed tranny. ($400-$600)
• The Marlin dual transfer case setup, the JP Eater dual transfer case setup, or a single granny t-case ($?)
• Gearwell Industries bellhousing1 (designed and fabricated by Marc Davis and the author) ($400)
• Toyota 22RE Turbo clutch disk (the friction surface with the little coil springs)
• Whatever other new Isuzu clutch parts may be needed: clutch plate, flywheel, etc.
• Gearwell Industries-modified throwout bearing and pilot bearing
• Gearwell Industries-modified transmission mount
• Modified driveshafts (Isuzu on the axle ends and Toyota on the t-case ends, lengthened accordingly)
• Pulley setup for the emergency brake cable
• Tools
• Patience
• Daring
• More patience.

The Actual Swap
Step one: disconnect the battery. Step two: take a deep breath.....

One of the harder parts was getting the Isuzu tranny off. First, you must remove the crossmember that supports the existing transmission mount. Next, remove the stock slave cylinder from the side of the stock bellhousing -- you'll use it with the new bellhousing. Careful removal here saves you from bleeding the clutch fluid later. Then move to the bellhousing. The bolts on the top of the bellhousing require some real wrist gymnastics to reach. Once unbolted, the tranny eagerly seeks out whatever it can crush, be they fingers, ribs, or glasses. Use a transmission jack even if you can bench press 200 pounds.

A quick look at the integrated Isuzu t-case/transmission reveals that it would be difficult to change the t-case gearing, so it's a good thing you bought that Toyota setup! Now comes that moment of committment: cutting the tunnel. You have to determine where your shifters are going to come up through the transmission tunnel, and cut new holes for them. Finding boots to fit them is pretty easy, and you can use a piece of blank sheet steel to cover up the old holes. Silicone it to ensure a good seal, otherwise you'll find nasty leaks when you're pulling Jeeps out of deep mudholes.

To start the installation, take out the Isuzu pilot bearing. Get the new Toyota pilot bearing, and press-fit it into the adapter ring...this allows you to put the Toyota pilot bearing in the Isuzu crank. Using a Toyota clutch alignment tool, center the clutch disk on the flywheel, then bolt the Isuzu clutch plate to the flywheel. It fits, doesn't it?

Next, bolt the Gearwell bellhousing to the Toyota transmission. Use plenty of threadlocking compound. Slip the modified throwout bearing over the collar on the tranny's input shaft, and fit the shift fork into the spring clamps. Mount the modified transmission mount to the tranny at this point, and leave the nuts off the crossmember bolts.

If you have decided on a dual transfer case setup, you'll need to remove a section of the center of the crossmember which sits just behind the torsion bar adjusters. This is needed to accommodate installation and to allow the driveshaft clearance. Leave the pieces of the crossmember attached to the frame, because they come in handy for mounting things like the pulley for the re-routed emergency brake cable. Now comes the fun part.

Install the transmission. You'll be delighted to find that getting to those top bellhousing bolts is much easier due to the new design, but if you don't have a transmission jack, you're in for a real workout. Once you have all the bellhousing bolts torqued properly, install the crossmember with the holes for the tranny mount in it, and tighten down the nuts. Easy, no?

Now comes one of the patient parts: getting the driveshafts. I recommend calling Tom Wood at Six States Distributors in Ogden, UT. He'll tell you what all he needs when you tell him what you're doing, but the gist of it is that you'll have to measure the distances and clearances needed for your particular setup. Then, you send him your old Isuzu driveshafts, he cuts them up, and makes new driveshafts which are mailed back to you as you sit in your armchair for days on end tapping your fingers until your wife files for divorce and your fingers are bloody stumps. Or...

Or you could get back to work. You still have to get shifters that will work, and these will require some modification. The easiest way to do this is to have an oxy-acetylene rig in your garage, and a pail of cool water. It will take some trial and error, but you should end up with a good-fitting pretzel that allows you to shift the tranny and t-cases.

Spend time making sure everything works. You still have to reinstall the Isuzu starter, and wire it up. Since I had the prototype, I decided that it would be a good idea to make sure that there was no obvious interference in the setup. I turned the engine over by hand using a socket on the crankshaft, just to make sure. Done. Good. Now hook up the battery again and crank it.

You should be able to put it in gear and not go anywhere. No, it's not that it's geared so low, it's because there aren't any driveshafts! Nevertheless, you can put it in low-low gear and see the output flanges turning...sloooooowwly....on the new Toyota t-case. Try the various gearing combinations, and enjoy the satisfaction that the crazy thing actually works. Try 2WD low range. Neat, eh? Make sure that you listen for unusual noises, however. If you hear grinding, it's probably because you forgot to put gear oil in the transmission and transfer cases. That will be hard on bearings in the long run, so you probably should turn everything off and do it now.

Even with the gear oil in, you'll notice that the new transmission is noisier. The low gears in the t-case make noise, and the Toyota tranny just doesn't shift as smoothly.

Once you get the driveshafts back, you're just about done. If you have the dual t-case design, you'll need to make doubly sure that the u-joint angles on your rear driveshaft are identical to one another. The decreased length of the driveshaft means that the angle is steeper, even approaching a critical angle for the u-joints. Lubricate them often, and listen for driveshaft vibration. If you hear some, and if Tom did your driveshafts, rest assured it's not because the shaft is out of balance. It means that you need to shim your axle one way or the other.

Crawling Around
Now the fun begins. See how slow you can go. Idle up a curb. Redline the engine while never exceeding the parking lot wheelchair speed limit. I did this modification a year ago, and I can honestly say that it is probably the best modification I've made to date. The control you have going over rocky trails is amazing. On slickrock, 2WD low range is incredibly useful, and you'll never hear a chirp from your tires. The bellhousing, clutch, bearings, et cetera have all held up wonderfully. Trust me...you won't be disappointed.

At this point, the bellhousing only fits certain models of Toyota transmission. Contact Gearwell Industries (George_Reiswig@ccm.jf.intel.com) to make sure that you get the right one before you buy it.