The Tanami Road is 850km of wide, graded, unsealed road (plus some bitumen). It will vary in condition depending on the weather and the timing of the last graders. It does carry some heavy vehicle traffic which can tend to chop it up somewhat.On any particular day its condition will vary from good to pretty ordinary. You will no doubt encounter some corrugated sections and the WA section always seems to be worse and can be stony.
Any vehicle in good condition and driven appropriately and with patience is capable of driving the Tanami (provided it is not wet, in which case nothing moves), but speeds may need to be quite slow in some areas.
Make sure you can carry sufficient fuel.

Cheers,
Peter