Hypothetical - 2.7 AWD conversion considerations (xpost from technical)

TL;DR:
Coming from the Audi/Quattro world and reading that the Manual FJ Cruiser's have a Torsen based AWD setup got (forgive the pun) my wheels turning. Would swapping in a Manual FJ Cruiser transfer case and carrier front axel get me full time AWD? And should such a swap be relatively easy on an already 4x4 truck?

Quattro goodness for kicks:


The long version:
My taco's a manual 2.7 4x4, but most of my research so far has turned up info on the 6 speeds/v6's. I'm trying to minimize my assumptions so I still have some things I am wondering about:

1. Do both R155F & RA60F transmissions have the same T-case bolt pattern? (based on what I've read, I'm thinking this is the case)
2. If the bolt pattern is the same, the next piece would be matching the Manual FJ T-case input shafts to the 5 speed transmission (with the R155F having a different number of splines), right?
3. If the T-Case can be swapped in, the rear driveshaft would need to be shortened to accommodate the T-case's longer length. Would the front drive shaft need adjustment too?

Then this is where it really starts to get murky for me. Keeping the stock ADD system, and pending the electronics are working correctly, is this feasible?

• 2wd (Front axles disengaged via ADD, center diff locked and sends all power to the rear)
• AWD (Front axles engaged, center diff sends power to front and rear, modulating in real time based on conditions)
• 4WD (Front axles engaged, center diff locked to split power 50/50 front and rear)

This would essentially keep 2wd, add AWD, keep 4High and remove 4Lo. (for simplicity, ADD could be removed altogether by swapping in the FJ front dif/axle carrier, removing 2wd and just keeping AWD and 4Hi) What electronic considerations are at play here? (controllers, ecu's, traction control systems etc)

Bonus: Am I totally nuts for rethinking a setup in an already pretty capable truck?

Here is why it's appealing to me in the first place:

• my truck is a daily driver. 98% of the time, it will only see street use. This does include snow though, and Quattro saved my butt many a time in the past.
• I will very seldom use 4Lo.
• 2wd for good conditions preserves my gas milage, while AWD for intermittent/bad conditions (like driving on partly snowy/icy pavement) prevents the need to constantly toggle into 4Hi.

What do you guys think?

 

If your swapping in a fj manual cas why would you lose low range? Those cases have awd, 4wd h, 4wd l......

 

You would need A LOT more than just a tcase and diff


-tcase
-front diff
-front/ rear driveshafts
-transmission
-hubs/wheel bearings
-cv axles

If you can get a good deal on these parts then go for it

 

You wouldn't need front diff, cv's, or hubs, wheel bearings.

The only thing different from an add fj/tacoma and awd fj front end is that it doesn't have an add tube, it has a straight direct pass through tube with no disconnect to the passenger cv axle.

 

Is his truck already 4wd..?

 

He mentions keeping the stock add system....... and is asking if his transmission t case pattern is the same as the fj's trans t case pattern

Also he talks about owning an Audi, and commuting in the snow....

 

Ha yes, I should have specified. It already is 4wd.

 

I should clarify. I don't think I would loose 4Lo knowing that the FJ's have 4Lo too, I just wouldn't have a need for it. Just thinking of ways to keep 2wd, have AWD, and then 4Hi (with the center diff locked)

 

Well you should be hypothetically able to manually lock the and manual lock the center diff.

Your front driveshaft will always be putting power towards the front diff though

 

hmmm nvm

op check out rock solid toys, they have messed with the fj case a good bit

 

Why go through all of the trouble of converting to awd and want 2wd? Afaik, on most awd setups, the rear wheels do more work than the front (60/40).

 

Weren't there some 3rd Gen 4Runner models that had full time 4WD as well, with just a hi and lo select? Maybe I'm crazy, but I swear I test drove one in 2002 or 2003 that was like that. Maybe if a swap IS possible, that would work too.

 

Yes you can get awd fj's and 4runners.... the tcase has a center diff with a locking option. The only place that they will be better in is on something like a snowy icy road. But driving selectable 4wd NON AWD trucks forever and i can tell you it aint worth the hassle to put the awd tcase in.... more shit to go wrong, more complexity for very very little gains.

 

I know with most Audi's (non S/RS variants) have a pretty modest split, and only hit that rear bias under some conditions. For the most part, they stay around 50/50. If popping back into 2wd is even possible, it would just be a perk of maybe a few more MPGs.

 

Off of the top of my head, I can't think of any vehicles that are awd that can be put into 2wd only. Maybe you want something that can be full time 4wd instead, especially if you're used to 50/50 bias.

Edit: if this is all about needing better traction on snowy roads, perhaps look into a good set of AT tires if you're still running stock tires. Can make a huge difference.

 

You will find a lot of ppl naysay projects like this. I say go for it. I think you generally have the tech concepts nailed down.

 

I'm not trying to sound like a naysayer. Just mentioning alternatives. @HomerTaco has an FJ transfer case in his truck. He might be able to help.

 

Sorry, that wasn't a comment directed at anyone. More just words of wisdom/encouragement to the OP.

 

There are two styles of FJ cases (maybe even 3)..... but i know there are at least 2. 1. is the one everyone wants cus they can do a twin stick manual setup.... 2. is the one no one wants which is the awd one with a diff in the tcase.


FYI, if you did keep ADD in the front with the AWD case you would have to figure out how to lock the center diff if you switched the front axle add to disengage otherwise you would go nowhere in"2wd".... but it would be pointless as you would still be spinning the front driveshaft and diff. AFAIK there is no way to drive just the rear output on the AWD tcase.

 

Ain’t got time to read the entire post....cliff notes plz