Forgetting to install the front CV axles would have the same symptoms as you describe. I'm not saying that's what it is but sounds like something isn't transferring power to the front wheels somewhere after the front driveshaft.
My brother forgot to install a stub shaft into the front diff of his FJ when he did his swap. I don't remember his symptoms but I didn't have to do it on mine because mine doesn't have ADD. I think you remove it from your old diff and install in the new.
Type this into your searchbar and you should be able to find a PDF from ECGS:
'05+ Tacoma, 4Runner, and FJ Cruiser Front Differential Removal Instructions'
The very last paragraph they call it a stub shaft.
I think it looks like this, I don't remember though:
[SOLD!] Front Differential ADD Gear Stub | Tacoma World
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2005 4R Sport 4WD
"The last of the V8s!" - Custom TIG'd SS Dual Exhaust - King 2.5" +2 LT. - ARB Front & Rear - 37's - Dana 60 -
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2005 Tundra 2WD Regular Cab V8 - Chopped Frame - Short Bed Swap
1977 Celica Liftback - LFX Swap -
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