thanks for posting this big mike. i didn't know there were so many types of gear cases.
1. what is the difference between short and tall style cases?
Generally speaking, tall cases were introduced in 1984 with the new all-aluminum transmission, the G52. The face of the cast iron 1979-83 L-series transmission's rear flange is about a quarter-inch shorter than the face of the aluminum G-, W-, and R-series transmission rear flanges. Therefore Toyota had to redesign the transfer case gasket and the transfer case's reduction housing's front flange to match the taller aluminum transmission.
To answer your question, the earliest tall case (Type 1-C) is no different than its short case predecessor: They both lacked the front bearing retaining clip and featured noise type gear sets. But this was a rare exception, and in general, the short and tall cases are, for all intensive purposes, contrasted as the short cases feature noisy gears and the tall cases featuring run-quiet gears. That is the biggest single difference between the two. All the bolt patterns, bearing centers, ribbing, gusseting, and structural design were unchanged.
Of course there are many non-related differences, such as flange style, speedometer sender gear teeth count, fill and drain plug style, shifting orientation and component configuration, and input spline count to name a few. These are all defined in great detail in the Bible. But for the most part, it is safe to say, in general, the only difference between a short case and a tall case is the type of low range gear components used (noisy or run-quiet).
It should be noted that short cases may be used behind the taller aluminum transmissions, and vice versa, however please take extra care in sealing the top portion of the mating flange when mounting a short case behind a tall aluminum transmission: There is only about a quarter-inch of gasket contact. We use Porter Manufacturing’s Gasgacinch (P/N 440) or Loctite's HI-TACK (P/N 30524) gasket-specific sealants in conjunction with the paper gasket to ensure the seal. Never, I repeat NEVER use silicone in conjunction with a paper gasket. You MUST use a proper gasket-specific sealant or pay the penalty of a leaking drivetrain.
2. if i have an 1980 and a 1986 efi case which one should i make the crawl box and which one should i put the 4.7's into?
To properly answer your question I need to know what transmission you are using. In general, we advise the shot case as the transfer case and the tall case as the Crawl Box. This is because our adapter plate is compatible with either style transfer case, and it is always a safe bet to build a tall case as your Crawl Box since it is compatible with either a short cast iron or a tall aluminum transmission.
While this general advice is the best in terms of getting a proper oil seal, there are valid considerations against it. For instance the tall case is younger and therefore may have less mileage than your older short case making it the better candidate as the transfer case. Tall case drive line flanges are superior to short case drive line flanges making it a better candidate as the transfer case. The tall case will more than likely feature run quiet low range gears, and since the average user is most likely to use the transfer case before the Crawl Box, it would be idea to use the tall case as the transfer case in order to maximize the amount of hours using the run quiet gear set while minimizing the amount of hours using the noisy gear set. This last point is not valid if plan on using our 4.70:1 XD gear set in your transfer case.
If your 1980 transfer case is a mid- to early-year model, then it is designed for a 4-speed transmission and will have a unique 4-speed input with a spline stepping design to prevent the transmission mainshaft from moving rearward. If you are not using a 4-speed transmission then this input gear will not work with a 5-speed transmission unless the diameter of this spline step is reduced. To help simplify this process, we designed the Chromoly coupler in our dual case adapters to be fully compatible with all 4- and 5-speed type transfer case input gears. Therefore, in this case, you'd be best to place your 4-speed 1980 case behind our Crawler adapter and run it as your transfer case and use the 1986 case as the Crawl Box.
You are certainly free to swap housings between transfer cases and use a short-cased run-quiet hybrid transfer case as your transfer case. Then you get the best of all worlds in one swoop.
3. what is the best year cases to make duals out of?
This question is highly subjective. Of course I could give the obvious answer as a 1986-87 Turbo (Type 4) transfer case since they have the strongest input gear design out of any other stock option, but this is not always the best answer. Especially if you plan on using our 4.70:1 XD gear set in your transfer case, both 21- and 23-spline XD gear sets feature a Total-Spline input gear that is stronger than the stock 23-spline Turbo input. This nullifies the only real reason why you'd want to use a Type 4 transfer case in the first place. Another disadvantage of the Type 4 case is that its forward shift configuration would need to be converted to a top shift configuration to use as a transfer case in a dual case setup.
Because these gear drive transfer cases were manufactured over a 16 year period, the age and mileage usage will vary greatly from core to core. Therefore perhaps the best answer would be to find the transfer case that has the lowest amount of mileage and therefore is in the best condition to be re-used. However, any gear drive transfer case manufactured after 1988 will be a forward style shift configuration and therefore will need to be converted as well.
Early transfer cases use the wrong flanges (9mm bolts with the smallest bolt pattern available). Newer transfer cases use the wrong shift style for a dual case transfer case.
Early transfer cases use noisy gear sets but are lighter than the newer transfer cases that feature run-quiet gear sets.
Newer top shift transfer cases feature an improved/stronger non shift rail c-clip design but as a result require more steps for disassembly.
Some 1992 and newer transfer cases use an electronic speedometer sender which may or may not be appropriate for your vehicle.
We believe the mainshafts of all 4-speed transfer cases are less brittle and therefore less prone to fracture (this has not been verified empirically), but now you are using a mainshaft that has at least 27 years of torque being transmitted through it!
And speaking of 4-speed setups, you may want to avoid this type because of the spline step considerations discussed above.
Have fun with your build and before you know you'll be out Crawling like the rest of us!!
<![CDATA[<a href="http://www.youtube.com/v/6LoQTme51tA?fs=1&amp;hl=en_US&amp;rel=0" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">http://www.youtube.com/v/6LoQTme51tA?fs=1&amp;hl=en_US&amp;rel=0</a>]]>BigMike
