Topic: Dual T-Case Info

[SiRMarlon]

I wrote this up a few weeks ago and I wanted to share this the MC Forum Members, hope you all don't mind

I know there are some thread with discussions and info on this but I figured hey I took the time to write this up so why not share it, plus it's always nice to have one thread with all this info in it.

So a couple of people have asked me whats "involved" in running dual cases and "What do I need". I figured it time to create a little write up and list everything that is needed. Over the last couple of months I've gotten really familiar with the inner workings of gear driven T-cases as I had to tear mine down and rebuild it, as well as doing my brothers case a few times and finally getting his Dual Cases set up! Needless to say it's been A LOT of fun learning about this stuff! I really enjoy rebuilding these and look forward to helping any of you guys out with building these up! 

So as for what's needed well that is quiet simple. It's not that complicated at all...you obviously need 2 gear driven cases but before we go on with that you first have to know what you have in your truck! There are 2 major differences amongst  Toyota Cases one being whether you have a "Top Shift" style case of if you have a "Foward Shift" style case.

What's the difference between both...

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This is your standard "Forward Shift" T-Case, you will notice that there is no shifter on the transfer case, and the shift forks stick out in the front of the case. The reason for this is because the t-case shifter sits at the back of the transmission housing.



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This is your standard "Top Shift" T-Case you can see right away that this one has a shifter at the top of the case thus the name "Top Shift"

[SiRMarlon [OP]]

Toyota for some reason never stuck with one or the other, they for some strange reason mixed and match according to transmission. With that said one thing you have to remember is that ANY FORWARD SHIFT transfer case can be converted to a "Top Shift" it's not that hard at all. All you need are the correct shift rails, and a shifter, shifter base. A couple of companies sell the kits ready to go:

Marlin Crawler Top Shift Conversion Kit $89

http://www.marlincrawler.com/hardware-tools/hardware/top-shift-conversion-kit-crawl-box



Inchworm Top Shift Conversion Kit $140 (The Whole kit is new)

http://www.inchwormgear.com/store/product_info.php?products_id=1009&osCsid=aec3dfbbbb8060fe76aa58766c54e0dc

[SiRMarlon [OP]]

Ok so now that we have gone over "Top Shift/Forward Shift" the next big difference between cases was the input shaft size. Toyota made 2 flavors of these, 21 Spline and the bigger stronger 23 Spline...

23 Spline on the left, and 21 Spline on the right...



Now which one do I have you may ask yourself? Here is a list of Toyota Transmissions and T-Cases according to shift style and spline count. This will give you a better idea as to what you may have. (list taken from Pirate)

Year Model Application Model Speeds Splines 1st Gear Engine Transfer Case:
1979-1980 Carb L43 4sp 21 spline 3.67 4cyl 20R Gear driven Top Shift
1981-1983 Carb L45 4sp 21 spline 3.93 4cyl 22R Gear driven Top Shift
1981-1983 Carb L50 & L52 5sp 21 spline 3.93 4cyl 22R Gear driven Top Shift
1984-1986 Carb G52 5sp 21 spline 3.93 4cyl 22R Gear driven Forward Shift
1986-1988 Carb G54 5sp 21 spline 3.93 4cyl 22R Gear driven Forward Shift
1986-1987 EFITurbo R151F 5sp 23 spline 4.31 4cyl 22RTE Gear driven Forward Shift
1985-1988 EFI W56 5sp 21 spline 3.95 4cyl 22R Gear driven Top Shift
1988-1991 EFI R150F 5sp 23 spline 3.83 V6 3.0L Chain driven Forward Shift
1989-1995 EFI W56 5sp 21 spline 3.95 4cyl 22R Gear driven Forward Shift
1989-1995 EFI/ADD G58 5sp 26 spline 3.93 4cyl 22R Chain driven Forward Shift
1996-2002 EFI W59 5sp 23 spline 3.95 4cyl 2.7L Chain driven Top Shift
1996-2002 EFI R150F 5sp 23 spline 3.83 V6 3.4L Chain driven Forward Shift

SO pretty much it's the R151F (Turbo Tranny), R150F (V6 Tranny) and the new Chain drive T-Cases that come with the bigger imput shaft...ideally a full 23 Spline Case and crawler box should be what you shoot for! But if that is not in your budget it's not a big deal. Most of us have the 21 Spline cases, and there is nothing wrong with the 21 spline case at all.

Now a lot of people always debated about should I just go with a single 4.7 gear set or should I go with a doubler setup. Well after Wheeling with both styles I've been sold on doubleing up, having the option of the stock 2.28 low range gear is really nice. There are a lot of times when the 4.7 is just to low to cruise around and 4Hi is well just to high. Yes there will be a bit more of $$ involved because of having to re-do your driveshafts, but in the end you will be happier. If you have never wheeled in double low its totally different, but in a good way of course! Everything slows down and it allows you to have more control.

[SiRMarlon [OP]]

So let's move on and talk about the "Crawl Box" What is the "Crawl Box" well that is the 1st case in line or at the front righ behind your transmission, this case you can use in either a "Forward Shift" or "Top Shift" depending on your transmission type. This is where your stock 2.28 gears will reside.

This is pretty much everything that you are going to need from your 2nd T-Case right here...these components make up the "Crawl Box"



Front "Crawl Box" with adapter bolted on already...this is the only thing along with the gears that is used from the 2nd transfer case.



If you really feel like splurging you can buy a brand new reduction housing from Adavance adapters but at $175 it's pretty pricey.

http://advanceadapters.com/product/3971/51-5911.html



Now that you have your reduction housing with your stock 2.28 (21 Spline or 23 Spline) gears you will need the doubler adapter, these are all pretty much the same it just depends which one you want, here is where you have to make a decision though do you want your input shaft coupler to be 21 Spline or 23 Spline. YES you can run a 23 Spline case behind a 21 Spline "Crawl Box" you just have to remember to order 23 spline gears for your rear t-case. You can also choose to run a full 21 Spline dual case setup. But just remember that the 23 Spline is stronger. Now as for the adapters here is the list of companies that sell them...

Marlin Crawler Adapter Kit $345

http://www.marlincrawler.com/transfer-case/dual-adapters/1979-95-gear-drive-mc07



Inchworm Adapter Kit $325

http://www.inchwormgear.com/store/product_info.php?cPath=21_89_92&products_id=28



And Advance Adapters Kit $325

http://advanceadapters.com/product/2456/50-5905D.html

[SiRMarlon [OP]]

Ok so now that you have your "Crawl Box" and your Adapter Kit, let's move on to your rear case. Off the bat YOU CANNOT USE A FORWARD SHIFT case in the rear. it MUST BE A TOP SHIFT so if you do not have a top shift case you will have to source one or convert your forward shift to a top shift in order for this to work! So remember front crawl box can be either Forward Shift or Top Shift(depending on transmission), but your rear case must be a Top Shift! No but's, if's, or ands about it! So now that you have your rear top shift case you have to gear it. The cool part of this is you can keep stock gears (2.28) in the rear as well and when placed in double low you are pretty much equivalent to a single 4.7 gear set. But I would highly recommend that you upgrade your gearing at this point with a nice 4.7 low gear for your rear case. Just the single 4.7 makes a world of a difference and your clutch will thank you! It's also at this point that you have to make sure you order the correct spline count (21/23) to match the doubler adapter you ordered. Remember if you want a stronger rear case order it up in a 23 spline flavor!

Marlin Crawler 4.7 Gear Set $445

http://www.marlincrawler.com/transfer-case/line-ups/single/new-4701-xd-gear-kit



Marlin Crawler 4.7 Competition Gear Set $549

http://www.marlincrawler.com/transfer-case/line-ups/single/4701-competition-chromoly-gear-kit



Advance Adapters 4.7 Gear Set $349

http://advanceadapters.com/product/2454/477021.html



Once you have everything together it's just a matter of tearing down and rebuilding your cases! It would also be a good idea that at this point you also order and install "Tripple Drilled Flanges" These range in the $20-$25 range.

Has all the common 1984-1995 patterns in one, universal output flange. Includes 4cyl CV and Non CV patterns as well as V6 CV pattern. Makes sourcing and reversing drive lines much easier. Fits gear driven transfer cases and 8" differentials

Marlin Crawler Flange $30 (on Sale for $10 at the moment )

http://www.marlincrawler.com/transfer-case/parts-upgrade/triple-drilled-tcase-flange

[SiRMarlon [OP]]

The end results should look something like this one...The front "Crawl Box" has stock 2.28 - 21 Spline gears, and the adapter is a 23 Spline Doubler because the rear case has a 4.7 23 Spline Low Gear set in it.



So now that you have your cases built and ready to get bolted on, it would be a good idea to invest in a nice new crossmember...in my eyes these are pretty much the same.

BudBuilt Crossmember $299

http://www.marlincrawler.com/armor/crossmember/budbuilt-budlite



Once installed you should have something like this...



Once you have gotten to this point then it's on to the next important step which is getting your driveshafts setup obviously your stock shafts will not work so they have to get re-done. Now there is no specific number for this since everyones truck will be a little different. So the way to do this is once you have your cases installed grab a measuring tape and measure the distance from the T-Case flanges to the Diff Flanges once you have this measurement you will have an idea of how long your driveshafts will need to be. Once you have your driveshafts done, bolt them up and go find some ROCKS!!!  

I'll see if I can put something together for the Chain Driven guys or maybe Wyatt can chime in with some info since he is the expert in that one!   Also if any of you guys have info or if I missed something just chime and add it to the thread!

[SiRMarlon [OP]]

If your rear-most case is out of a 1985 to 1988 top shifting EFI (W56-A/B) tranny then you must shorten the driver's side shift rod. This is the shift rod sticking out of the rear most case when you shift into 4hi that has the flat side on top. You must trim 1/2" off of the front of this shift rod to avoid jamming between the two cases.

Thats a nice little tid-bit that I didn't notice right away.  I was about to bolt on my rear case then I noticed it and hacked it off with a grinder

Yup that's right I forgot about that little piece of info...here are some pics.





This is so it doesn't interfere or hit the back of the doubler adapter. I did the same thing once I went to bolt on the Crawl box, just whipped out the good ol grinder and cut it right off

[SiRMarlon [OP]]

Ok someone just asked me a question on Lubrication (gear-oil) and filling the cases.

The T-Case and Trans get their own oil they do not share, when you have dual cases it's important to check both cases. Also as far as filling the cases it's really simple, there are 2 methods to doing this. The 1st one is to fill the 1st case like you normally would (1.7 quarts I think, someone correct me if I am wrong), once you have filled it up add about another quart in through the top shifter base of the "Crawl Box".

The other method is fill the rear case like you normally would and then drive around a bit so the oil reaches the front case and then top it off again. But personally I think the 1st method would be best.

If I have these wrong someone please correct me

[kneedownnate]

You're gonna want to remove all those trail gear links 

[SiRMarlon [OP]]

You're gonna want to remove all those trail gear links 

And why would I want to do that? Are there rules against posting products from TG? Instead of suggesting me to remove my links why don't you add something constructive to the thread instead. If you guys are going to turn this into a TG vs. MC thread then I will just take the whole thing down. I was just trying to help out all those people who have questions in regards to doing this setup without having a biased mind about it!

[dntsdad]

I appreciate  your work and your post as a newb in the world of cases and adapter and such.

However, I think if you step back and think about it rationally, you would agree that posting link to a competitors site, and even moreso knowing the history of Marlin Crawler and Trail Gear, is probably not an acceptable thing to do.

You must remember that this is NOT a public, neutral forum. It is biased! Marlin pays the bills on this forum and posting links to his competition is unseemly in my opinion.

I doubt that if you ran a business, and had competition, that you would want people to post links to the competition's product that rivaled your own. If you did, you may not stay in business long.

Marlin is nice enough to offer this forum for people to share information, and support and sell his products. Promoting the other company's product is not probably one of his objectives.

[OOPS]

Nice work!!!

I will put it this way, go to TG's forum and post pictures and links to Marlins site and see what happens.

[crazykooter]

Personally I dont care for most TG stuff but I believe MOST if not all here respect Marlins products and understand the diff between the 2. So posting links to TGs stuff isnt such a bad thing since its a good reminder why we are on Marlins site and spend our hard earn dollars on Marlins products. 

On topic well done on the write up.  Looks good !!  Glad to see ya caught the shifter rod.  Sucks having it all together and then go and put it in 4h front and 4L rear only to have the dang rear shifter rod push the front case into neutral. 

[SiRMarlon [OP]]

I totally get what you guys are saying...but I think the person could have just PM'ed me and given me the reasons instead of just coming on here and saying you might want to remove the links. I've got nothing but respect for Marlin and everything he has done for the Toyota Community!

[YotaNate]

Well done!  Awesome info and pic's!   


Nate

[mtm]

loads of info there top job

[kneedownnate]

I totally get what you guys are saying...but I think the person could have just PM'ed me and given me the reasons instead of just coming on here and saying you might want to remove the links.

I merely made a suggestion based on having been on the forum quite some time and knowing what's gone on between the two and how tg came to be.  You can take it personally or do with it what you will 

[907yota]

good info here thankyou!!! i recently purchased an 86" turbo reg cab 250,000 miles and still pulling... going with duals is in the future after the swap...I scored a front axle and transfer case out of an 85. dont know if i missed it or not, but will i be able to run this case with my 23 spline from my turbo case? or would it be easier to order up a built 4.7 W/ 23 spline and adapter? and use the other case for the core charge

[2manytoys]

I'm planning on duals in the near future. Since it's sometimes the little stuff that can shut you down I have a couple questions.

Is a speedo cable extension a must?

Do you have to lengthen the switch wires at all?

Got any pics of the floor mods needed, shifter covers, shifter mods for clearing bench seats?

Thanks for the write up.