Toyota employed at least 12 different separate transfer cases in Pickups and 4Runners from 1979 to 1995. It’s crucial to comprehend the variations between the transfer cases and how to select the right one for your application when choosing a replacement for a Trail-Creeper.
Chain drive vs. gear drive
Chain drive style transfer cases are those that connect the front drive with a chain. “Gear drive” transfer cases are those that operate without a chain and with direct gear contact. Chain drive style transfer cases are typically installed in trucks with automated transmissions and/or V6 engines. A chain drive case is also included in some later model 4Runners with a manual transmission and a w58 transmission. Looking at the transfer case’s rear cover and counting the number of bolts holding it in place will quickly reveal whether a transfer case within this year range is chain- or gear-driven. It is a gear driven case if the cover contains 7 bolts (as indicated in the photo). It is a chain drive style case if the rear cover contains five bolts. At present time, none of the chain drive applications are supported by Trail-Gear.
Forward shift versus top shift
“Top shift” style transfer cases are gear-driven transfer cases with a shifter that protrudes from the top of the transfer case. Some transfer cases can be shifted using shift trails and a shift lever that is mounted on the top hole and a block off plate that is fitted on the top hole of some transmissions. A “forward shift” transfer case is the name given to this kind of transfer scenario.
A dual transfer case assembly’s rear case must always be a top shift case in order to shift the rear reduction housing or the 2wd/4wd portions. A dual transfer case’s front reduction section can be either a top shift or front shift design. A forward shift transmission typically pairs with a forward shift case. Toyota utilizes 4.5″ and 4.0″ reach shift forks, respectively. The transfer case shifter won’t operate properly unless the appropriate shift forks for the transmission are utilized.
23 or 21 spindles:
Between the transmission and the transfer case, 23 spline gears are used in all 19861987 turbo installations. The 21 spline gears are used in all other gear-driven applications in this year range. These gears differ in that the 21 spline sections are slightly smaller and weaker than the 23 spline components.
It is advised to utilize a 23 spline dual case adapter and a 23 spline rear case input gear when installing a dual case into a vehicle with a 23 spline output transmission (such as a turbo or V6).
A 21-spline input gear must be used on the front reduction housing of a twin case system in applications that use a transmission with a 21-spline output. In this application, the front and rear reduction sections may be connected by gears with 21 or 23 splines. A 21-spline coupler should be used on the dual adapter if a 21-spline input gear is utilized on the rear reduction unit. A 23 spline coupler should be used on the dual adapter if a 23 spline input gear is utilized on the rear reduction unit.
On all dual transfer case installations, we highly advise the use of 23-spline components between the front and rear reduction units. Hardware with 23 splines is stronger than hardware with 21 splines. With a stock or lightly built 4cyl motor, this is not an issue at the point where the transmission and transfer case meet. When the transfer case is in low range, the torque is amplified by a factor of 2.28 as engine power is transferred via the first transfer case into the second case. There is 2.28 times as much torque applied to the rear input gear/coupler as there is to the front input gear/coupler when both reduction sections of a dual transfer case are engaged.
Core Fees: Both single and dual TrailCreeper transfer case units have a $200 core fee. Crawl box units have no core charge. The core charge is included in the transfer case prices indicated above. After the unit has been inspected, you will be given a business check for the core amount when you return your old core case. The use of disassembled cores is prohibited. Gear and bearing damage is permissible. Housing components with damage are not allowed. Cores must be finished, put together, and in a rebuildable state. Please send core a copy of your invoice. The expense of delivering the core back to the customer. Case Transfer Oil:
Oil-free transfer cases are shipped. Gear oil made from GL5 should be 8090wt in the cases. Around 2 quarts of oil are used by a single transfer case. About three quarts of oil are used by a dual transfer case. The rear fill plug visible in the photo can be used to fill both single and multiple units. Check the fluid level after a brief drive if you are filling your transfer case for the first time. The fluid level must match the fill plug opening exactly. After 1,000 miles and then every 30,000 miles after that, fluid should be changed. You can use synthetic oil, which will cut down on friction and internal wear. Levers for shifting gears are not sold with transfer cases.
What distinguishes my transfer case model?
Frequently, what is garbage to one person is gold to another. In light of this, we are profiling a few OE transfer examples from U.S.-brand applications that are enthusiast-worthy. It should make low-cost buying in the classifieds or the junkyard more manageable.
Transfer situations involving New Process/New Venture are simple to spot. Newer models have a round red/silver/black tag on their undersides, whereas older models have a rectangular ID plate screwed to the rear of the casing. An assembly tag for BorgWarner models is fastened by one of the housing’s fasteners.
The majority of Detroit Three transfer instances are summarized in the accompanying graphic. Listed dates may not always correspond to car model years but rather manufacturing years. Additionally, each transfer case model may come in a variety of forms depending on the year and application. Unless otherwise stated, all postings are part-time and chain-drive/aluminum case.
Ford GPW 7700, Model 18 Dana/Spicer Identify: Oil pan, rear PTO, output-mounted drum emergency brake, output offset to the passenger side, dual sticks on most models. Early Ford and Bantam variants installed with the driver side dropped. Early Military (19411945): MB and GPW applications used a 1.97 low-range. Rare: Early Civilian (19451946). They arrived in the CJ-1 and the initial CJ-2s; low-range 2.43. 2.46 low-range; bigger 118-inch-diameter intermediate idler shaft for the mid-civilian (19461955) period. Later Civilian: The intermediate shaft’s diameter was raised to 114 inches (19551971). Final Civilian (19661971): Rear locating bore raised from 3532 inches to 4; single stick; uses Dana 20 case casting. Gear oil in the 85W-90 range. Notes: The PTO port was frequently installed with overdrive units. While some Ford GPWs used the 2.46-low Ford GPW 7700 transfer case, some had the Early Military Model 18.
Spicer/Dana Model 20 Identify: Rear output is centered; single shifter; similar casting as the later Model 18 2.0, 2.34, and 2.46 are low-ranges. the 85W-90 gear oil lubricant Notes: Versions also showed up in 4x4s made by Jeep, IH, Ford, and Chevy. Various variants can use the same parts. The Bronco had a T-shift with a 2.46 low-range from 1966 to 1972, while cars from 1973 to 1977 had a J-shift with a 2.34 gear ratio. A 2.46 low-range can be produced in Jeep and IH Model 20s by combining the sliding gear from the Bronco Model 20 with the gears from the Model 18.
Spicer/Dana Model 300 Identify: Single stick, 6-bolt round mating surface, aluminum tail housing, passenger-side front output, centered rear output. Minimum: 2.62 Oil lubricant: gear oil 80W-90 Notes: The endurance and 2.62 low-range of this OE Jeep transfer case make it conceivably the best. The rear output housing on the 1980 model is 312 inches long. In 1981, this was raised to 512 inches to accommodate bigger speedometer gears. The aftermarket Atlas transfer case was based on the Model 300.
BW 1305/BW 1339 Identify: The metal chassis is split laterally, the outputs are skewed to the passenger side, and the 1339 models (pictured) include a gear-reduction box. Minimum: 2.57 (BW 1339) Special fluid is a lubricant. Notes: The Quadra-Trac BW 1305 transfer case was the first mass-produced chain-drive/aluminum-housing transfer case, and it was introduced in the 1973 Wagoneer. This permanent device lacked a low-range. A planetary gearbox was added to the BW 1339 variant to create a low-range. This transfer case has an internal differential that can be locked using a vacuum switch positioned on the glovebox to uniformly distribute torque front to back. Although MileMarker sells an overdrive chain and a kit for part-time conversion, rebuild parts are uncommon. It is a direct successor for the Model 18.
How can I tell if I have a transfer case under NP205?
Although the classic NP205 transfer case has a reputation for being rock-tough, the truth is that it is much more resilient. Watch the chips fly as this cast-iron beauty slams against a trail boulder.
If using this unit on your wheeler for that reason isn’t challenging enough, we don’t know what is. The NP205’s meager 1.96 low-range reduction is its only significant flaw, however it can be fixed with future modifications and aftermarket doublers. This geardriven case has been subjected to extreme punishment from big-block torque, monster tires, and running with water in the oil, and its tenacity has continually astounded us. In reality, we really doubt that this unit, when built and maintained properly, could suffer major damage.
As early as 1969, the 205 was available in GM, Ford, Dodge, and International trucks. It continued to be manufactured in GM trucks until the middle of the 1980s, when the NP208 finally took its place in all applications with the exception of cab and chassis trucks, which continued to use the 205 until 1991. The legendary 205 was produced in remote and married versions, lefthand drops for Ford and righthand drops for the others, and late-GM applications even included a slip-yoke rear housing. The center cluster gear and core case design of every unit stayed the same over time, despite the usage of various input and output shafts. An NP205 is relatively simple to recognize: It is roughly 12 inches long, has a center rear output, a cast-iron housing, a center idler shaft with a nut on the front and a three-bolt cap on the back, and typically has an ID tag above the front output shaft.
Many cars from all manufacturers from the 1970s and 1980s have the incredibly durable NP205 casing. Performance Gear & Axle cleaned and examined the case bores on the GM unit we chose, which has the drop on the right side, before we got started. Our ’70’77 GM case with direct mounting was identified by the casting number (C99404) on the left, which is almost exactly what we were looking for. The mid-1970s Ford case to the right has direct mounting and a left-hand drop. Prior to the widespread six-bolt round pattern’s introduction, the eight-bolt racetrack pattern, visible on the GM case from 1971 to 1985, was in use.
Since we have no plans to keep our 205 stock, we went to Performance Gear & Axle in Mississippi to have a unit built to our precise requirements. In fact, Performance Gear & Axle took a 205 out of stock specifically for this rebuild because we already had an NP208. With its own line of adapters, Performance Gear & Axle can even mate a Clark five-speed to a Dana 300 transfer case or an NP205, earning them a stellar reputation for creating uncommon driveline combinations. The business even sells replicas of factory-style adapters for the difficult-to-find TH400 and TH350 to NP205, as well as one for the unproduced 700R4. For those of you who have your front diff on the left side, the manufacturer even has a specific bearing available to run a lefthand drop behind Chevy and Dodge trannies. After discussing the many variants that have been found in the 205 over the years with us, owner Ed Hotard created a great formula just for our needs.
We chose to go for maximal robustness and adaptability because our application for this bulletproof 205 project is our 1985 GMC 2500 3/4-ton with a TH400 tranny and an NP208. Since the case of our current TH400 was cracked and we could sell the functional 208, we made the decision to rebuild the TH400 for use with a stock TH400-205 application. The least amount of changes were needed for this combo because it is the shortest and powerful. We added an Off Road Design Doubler since we thought the 1.96 gear ratio in Low was a tad on the flimsy side. The Doubler, which is intended to bolt between the transmission and transfer case, is essentially just an NP203 low-range reduction unit. This increases the gear reduction and provides us with a wide range of wheeling alternatives. For moving the 205, we also want the twin-stick modification, which Off Road Design also provides. Our revised strategy called for using the tranny’s stock TH400-to-NP203 output shaft so that the Doubler could be installed quickly. Then the NP205 from Performance Gear & Axle would bolt into the adaptor from Off Road Design. We wanted something that was sturdy, clear, and easy to use, and this would be ideal. For ultimate longevity, we even updated the front output shaft. See how we assembled the transfer case with this collection of components, and hold off on viewing the trick TH400 and Doubler installation until a subsequent issue.
Case Differences Only a few of the many versions of the NP205 are shown below. Different male or female input-shaft diameters, left or right drops, adapter bolt patterns or remote styles, unusual things we’ve never seen, and other peculiar things all work together to give the revered 205 a mysterious atmosphere. The Ford remote mounted with a permanent yoke on the input shaft (B), the late-style GM with a slip-yoke rear output, and the early-model GM with an eight-bolt racetrack layout (A) are the most popular variations (C). Even input bearing diameters differ, so check yours by measuring.
The TH400-to-NP205 combination is the best choice for extreme strength and durability. Although the six-bolt circular mounting surface and long female input shaft make for a fantastic package, we choose to approach things differently. This device, as illustrated, wouldn’t function because we planned to use an Off Road Design Doubler between the two. For the most compact package, we needed the shorter one with the eight-bolt racetrack pattern mounting as it includes a long 32-spline female input.
The 205 case with the TH350 fastened to it, which has a smaller input-bearing diameter than the TH400 application, is the more typical one for GM vehicles. Fortunately, if you have the correct tools, you can easily bore the orifice out to the bigger size. These upgrades have been completed frequently by Ed Hotard of Performance Gear & Axle, who also sets up his enormous machine for fine machining.
We set up all of the elements for this picture after deciding which ones we wanted to use. Low range gear, front output, rear output, cluster, and input. Clutch sliders and low range gears are identical; you’ll only find them on different sides of the case.
Tapered roller bearings support the middle cluster, or idler gear, at both ends. The thrust loading of the helical gears makes this significantly superior to needle bearings. Shims are used to adjust the bearings, and holes in the spacer between the bearings and the gear and shaft allow oil to pass through. The most crucial location for oil flow is within the holes, so make sure they are all clear of impediments.
Front-end beef The front output shaft with 10 splines and 1.25 inches was standard on early NP205 units. Even while the 1.25-inch, 30-spline shaft on later models is stronger, it isn’t the greatest option. For serious beef, we went with the Ford and Dodge models’ 32-spline, 1.401-inch shaft.
A 1310 series U-joint, CV, or 1350 U-joint uses a 10-spliner. The Saginaw type or the 1310 CV or 3R CV were compatible with the 30-spline. A yoke for a 1310, 1330, 1350 CV or U-joint, as well as the 1450 size joint and a few more odd alternatives, can be used with the hefty 32-spline. This is the one for you if you require the power of the largest.
Changes in Gender There are several input gears available for the 205, but male (external splines) and female are the primary differences (internal splines). These three female input gears were used by the NP205. Short 32-spline for the TH400, long 32-spline for the TH400, and 31-spline for Ford applications are shown from left to right. The ideal setup prevents excessive slop from developing by having the transmission output shaft fit directly into the input gear without the use of a sleeve. For our bulletproof 205, we went with the short 32-spline.
Additionally, GM employed external-spline input gears that needed a sleeve to link to the transmission. The fixed yoke for remote use, the early SM465 manual transmission’s 10-spline, the TH350’s 27-spline, and the early Dodge diesel manual applications’ 29-spline are shown from left to right. The 23-spline for Dodge gas engine and diesel automatic applications is not visible here.
It’s Twin-Sticking One lever controls two shift rails on the regular 205 shifter, which provides high 2WD, high 4WD, neutral, and low 4WD. Although these shifters are no longer offered, Performance Gear & Axle still manufactures stock-style alternatives for Ford, Chevy, and Dodge vehicles. The interlock pin between the shift rails in a stock 205 forbids any other combination of positions, which is both advantageous and disadvantageous. For the same positions as stock, as well as low rear-wheel drive only and low front-wheel drive only, we choose independent control of the rails. The case can be set into high and low range simultaneously if the interlock pin is simply removed, although this is not a good thing.
Without having one in low and the other in high, you may get high, neutral, and low out of the front and/or rear output by appropriately changing the rails. Range and mode shafts need both be modified, but we decided that a set of modified rails from Out Road Design would be the best option because the detents and reliefs are precisely machined rather than relying on a guess as to how much should be ground off. We will have all the options we require thanks to ORD’s twin-stick adaptation. Check see “Twin-Stick 205”, a piece about DIY twin-stick mods to accomplish the same thing, if you must do it yourself.