Top Shift Mod

Toyota sold more 4wd Pickups & 4Runners with a forward shifting style transfer case, so it can sometimes be difficult to find a good used top shifting donor transfer case for your projects.

This is a fairly simple job that can be done by anyone (2-3 hours depending on tools and skills) that can turn a wrench and does not a have short-term memory problem. Or maybe using the famous banana scale, I'd give this 3 bananas. There is only one thing that may stop you from doing this mod all by yourself. This would be the removal of the flange(s). If you do have a problem you should be able to take the transfer case to any repair shop to have them removed.

Note: Throughout this article the parts are listed (when first mentioned) in red with a number after them in { }. This number indicates the part on the Exploded view of the transfer case. See picture at the bottom of the page.

6mm Hex Wrench
22mm Wrench
12mm Socket
14mm Socket
30mm Socket
3/16” Punch
Flat Head Screwdriver
Magnet or Surgery Clamps
Snap Ring Pliers (optional)
Impact Wrench (a Breaker Bar and Vise or Chain Wrench will work)

For Floorboard Mod:
Drill w/ 1/4” bit or 3 1/2” Metal Hole Saw bit
Sawsall (not needed if Hole Saw is used)
Hand Grinder (may not need)
Metal File

Top Shift Kit - $80 +$40 core (Marlin Crawler)
Transfer Case Gasket Set - $30
Transfer Case Flange Seals - $8 ea.
Shift Boot - $10-$30

The first thing that you need to do is remove the transfer case from your rig. See your repair manual for the proper procedure on this.

After you have the transfer case removed set it down in a clean area with enough room to set the parts out so that they are out of your way and you won't lose any of the smaller parts.

Let's start off with seeing if we can get the Flange(s) {1} off. I like to take them both off so I can replace the seals and gaskets while I'm tearing the transfer case apart anyhow, but only the rear flange is necessary to be removed for this mod. What makes this part sometimes a bear to deal with is the pinch nut that holds the flange on. This is where the shaft that the nut screws on to has a slot in the side of it and the top half of the nut is punched into the slot. Thus locking it so it can't spin itself loose. What you need to do here is use a small flat head screwdriver that will fit into the slot and use a hammer to knock it down behind the pinched part of the nut so you can pry it back out. Most of the time this goes well, but sometimes, well…maybe not so well. After getting the pinched part of the nut out (make sure it's out passed the tread) use an impact wrench with a 30mm socket (one hand on the flange to keep it from spinning). If you do not have an impact wrench handy then if you can put the flat part of the flange into a vise with something supporting the transfer case so that it's not baring its weight on the shaft; then yon can use a breaker bar. If a vise is not feasible then try a chain wrench on the Flange to keep it from spinning and a breaker bar. Wrap the chain around between the flange and the dust cover. Be careful not to crush the dust cover too much.

Good luck. And remember as I mentioned, if needed there's always the repair shop.

Ok, got the flanges out of the way; then let's take this baby apart.
With the 22mm wrench remove the Transfer Indicator Switch {2} . Remove the Speedometer Driven Gear {3} . To do this, remove the bolt and hold down plate then it should just pull out (may need to wiggle it a little). With a 14mm socket remove the (7) bolts (red arrows) to the Extension Housing {4} and then remove it. The snap ring around the Idler Gear Bearing {5} can be removed or it can be left on so that the bearing and shaft within pull out with the Rear Case {6} . Next take out the (10) bolts (blue arrows) to the Rear Case and remove it. With the Rear Case off you'll see the Speedometer Gear {7} on the end of the Output Shaft {8} . As you can see in the photo I wrapped electrical tape around the end of the Output Shaft. Underneath the Speedometer Gear is and steel ball that makes the gear spin with the shaft. The tape holds the gear on form sliding off so there are fewer parts to keep track of if needed. If you removed the snap ring from the Output Shaft then you can now remove the shaft and bearing assembly.

On the each side of the upper half of the Front Case {9} you'll find a Plug {10} that can be removed with a 6mm hex wrench. The Springs {11} and Balls {12} within can be removed by turning the case to each side so they fall out. With a 3/16” punch and a hammer remove the roll pin from the Rear Shift Fork {13}. After the pin is out you should be able to slide the Front Drive Shift Fork Rail {14} from the Reduction Gear Case {15} and then remove the Rear Fork. After the rail is out tilt the case to the right side to let the Interlock Pin {16} slide out. If it does not want to slide out then light tapping to the case with a hammer or a quick burst of air into the rail guide hole will usually get it to come out. Next with a 12mm socket remove the (4) bolts to the Transfer Case Cover {17} (Shifter Base shown) and put it on the back of the transmission where the shifter was.

If you look down inside the Reduction Gear Case you will see the Front Fork {18} and the High-Low Shift Fork Rail {19} (left rail). Again with a 3/16” punch and hammer, punch the roll pin out. You can either punch it all the way out so it falls inside the case and retrieve it when you pull the cases apart or you can punch it through while someone else holds a magnet underneath the rail to catch the pin before it falls. What I like to do is punch it half way out and clamp a pair of surgery clamps to the pin. Then punch it the rest of the way out. Either way you go, with the pin removed the rail can be pulled out. And at last remove the last (2) bolts on the front of the Reduction Gear Case and pull it apart from the Front Case. Remove the Front Fork and put it and the rails aside. They're history.

If they were shipped assembled then start off by disassembling the new Fork and Rails. Use all new gaskets and put a thin coat of white grease or gear oil on all new parts before installing them. Place the new Front Fork (shifting forks facing inward) on the Input Shaft {20} and bolt the Reduction Case back on to the Front Case. If the Oil Pipes {21} happened to have fallen out while pulling the cases apart don't worry. They slip right back into the holes and are easy to figure out which way they should go by look at them and the case. Put them into the Gear Reduction Case and bolt the Front Case on. As you put the Front Case on watch to make sure that the Oil Pipes are aligned with the holes in it. Side the new High-Low Shift Fork Rail (shortest one) through the left rail guide hole in the front of the Gear Reduction Case and into the fork. Align the holes in the rail and the fork with the three notches on the rail facing outwards and tap the roll pin in. From the right side of the Front Case, slide the Inter lock Pin back in and slide the High-Low Shift Fork Rail into the high position. This will be when the Inter Lock Pin is not sticking up into right rail guide hole. Hold the Shifting Fork {22} down inside the Gear Reduction Case and slide the Front Drive Shift Fork Rail through the right rail guide hole. Don't slide it all the way out the back of the Front Case. You'll need to put the Rear Shift Fork onto the Clutch Sleeve {23} first and then the rail through the fork. Again align the holes on the fork and rail and tap the roll pin in. Be careful not to hit the case, there not a lot of room here. After the roll pin is in then do it one more time with the Shifting Fork (fork facing in). Put the Balls, Springs, and Plugs into place.

Install the Idler Gear and the Rear Case. Don't forget to remove the tape on the end of the Output Shaft. There are two different size bolts used to hold the Rear Case on; make sure you get them in the correct holes.

Remove seal form the Extension Housing and install a new one. Bolt the Extension Housing to the Rear Case. Then install the Flange(s), Transfer Indicator Switch, and the Speedometer Driven Gear.

At this point you should have no other parts laying around except maybe the old Front Fork and Rails. If this is the case then install the shifter and test shift to make sure all is working correctly. If it works good then let get to cutting up that floorboard.

Remove the shifter form the transfer case. If the have an extra Transfer Case Cover then put it on to keep any dirt or debris from falling inside the case (a clean lint free rag will do to). You can also make a simple temporary cover out of a piece sheet metal. Just cut it larger then the hole and drill two holes caddy corner form each other through it for bolting it down. Install (w/o bolting it) the transfer case and mark a 3 1/2 “ circle where the shifter will go through. Use the hole saw to drill the 3 1/2” hole. Or you can use the 1/4” bit and drill several holes around the circle and a sawsall to finish and clean up the jagged edges. Next reinstall the transfer case and bolt it up along with cross member, driveline, etc. Install the shifter and check for clearance between the shifter and the floorboard while shifting. Remove the shifter and recover the top of the transfer case. If the clearance was good then use the metal file to clean up any sharp edges and install the shifter and new shift boot. If more clearance is needed cuz the shifter hits the body and won't let it shift into other gears then use a hand grinder to make a little more room and then recheck it. For fine-tuning the shifter position you can use a metal pipe over the shifter to bend it.

Parts in black that are not in the article:

24. Bearing Retainer 28. Spacer 32. Bearing Retainer
25. Clutch Sleeve 29. Needle Roller Bearing 33. Front Drive Gear
26. Output Shaft Rear Bearing 30. Transfer Drive Gear 34. Bearing
27. Oil Pump Screw 31. Clutch Hub 35. Counter Gear


The information provided above was submitted by a visitor to takes no responsibility for the accuracy of the information above., it's owners, or Toyota Motor Company deny any liability for actions taken based on the information in this article and will not accept responsibility for damage incurred to any vehicle, parts, or person, based on those actions.  As always, encourages its visitors to seek the advise of a professional before attempting any modification to any vehicle.

 Always wear your seatbelt, drive safely, and keep your wheels down.