Can You Convert Your Full Time 4WD Toyota/Lexus T case To Manual Shift Full Time 4WD?
As our 4th gen 4Runners, 2003 to 2009 and our 2004 to 2009 Lexus GX 470's get older, the transfer case's are starting to have issue's. Leaks are occurring more often and when we get the actuators wet and dirty they stop working all together.
One of the beauties behind these vehicles is that they are full time 4wd, (with the exception of the V6 model 4runner which has full time 4wd, 2wd and part time 4wd functions). With this full time 4wd system they are great vehicles in the snow and rain. They are very stable in most inclement situations.
With those attributes it's no wonder that some folks would like to keep this system in their vehicles, however they would like something just a bit more reliable. Say something like the manual transfer case found in the FJ cruisers. No electronics to foul up and you get that trusty shift lever that never fails you.
So why not just drop in the full time manual transfer case from the six speed FJ Cruiser into your 4th gen 4Runner or GX470? Seems legit right!?! Wrong!
There are a number of reasons why this conversion either wont work or is way too involved to even be worth it. So lets go over the reasons why this isn't a viable conversion for your V8 4Runner or GX 470.
Reason number one. The two transfer case's are not compatible.
The 4Runner and GX use a transfer case that has a female coupler on the front of it that goes into the back of your transmission that has an internal male output shaft.
Notice the coupler on the front of this transfer case. Although this is not the transfer case from the 4Runner or GX470, it is the same input, coupler and bolt pattern. It'll bolt right up to your A750F transmission with no issues at all. So why can't we just use this? We'll get into that later.
Now the transfer case below is the full time 4wd version from the Six Speed FJ Cruiser. Notice how the input on this case has a male 22 spline input and it's much larger than the one on the above transfer case. Now, even though this case has the same bolt pattern as the OEM t case in the 4Runner and GX470, the input wont allow it to go into the back of the transmission.
So then the question came up, why don't you just swap out the planetary gearsets like you do on other swaps? Tried that. You would think that Toyota would use the same internals since they both are using the Torsen center differential but for some reason there is a difference between the two that wont let them swap over. Thats a drag.
OK, so since that doesn't work why don't we just throw the t case from the FJ Cruiser with the automatic transmission in behind that auto trans of the 4Runner and GX and call it good? It'll bolt right up, it has the 23 spline input that we need and other than some modifications to both drive shafts, getting the shifter into the cab and some sensor wire work, it'll be good as new. Not so fast.
You see, the FJ Cruiser transfer case that is behind the automatic transmission was never meant to be a full time 4wd case. Drive it on asphalt while in 4wd and since it's sending equal amounts of power to both the front and rear at ALL times you'll run into binding issues while going around corners that will quickly shorten the life of that Transfer case. And if that is not enough, the spinning of the chain inside at highway speeds will cause blow by of the oil through the shifter base. eventually this will cause a problem as well.
A young man brought his 4th gen 4Runner to me years ago complaining of grinding noise in his t case. He never mentioned that he had put in the Fj Case in his V8 4Runner and drove it for six months like that. It ran low on oil from leaking out of the top and burned up his bearings. Once we changed the t case and put in the true part time front diff he has been hassle free for three years now.
As you can see, it's not so simple to convert your full time 4wd transfer case into a manual version. If you want the reliability of the FJ case then I suggest you turn your full time 4wd into a part time system. If you want the attributes that the full time 4wd system brings in inclement weather then I would just bite the bullet and either purchase another electronic case from Toyota or Lexus, OUCH, or cross your fingers and hope the junk yard hasn't sold you another lemon.
I like the full time 4wd system in these vehicles, however, not enough to spend all that money on another electronic transfer case that'll just fail me again when I make that deep water crossing leaving me stuck in the middle of nowhere. I'll just drive sensibly in the snow and rain like I always have way before these vehicles came out and enjoy the confidence to know that when I truly do need my 4wd, it'll be there when I ask for it.
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Thank you, RST