I was changing fluids today and my son wanted to pump the diff fluid (VTM-4) to "help dad". Apparently the big container of "VTM DIFFERENTIAL FLUID" beside the diff seemed too convenient and I find him pumping the transfer case gear oil into the diff. He had almost the full quart in. I immediately drained it but what do I do now? Is it enough to flush it with a new full 4 qt bottle of VTM-4 and then fill with another new 3 qts?

 

I think your best bet would be to drain as much as posible and refill with fresh VTM-4. Go out and do some figure 8s in an empty parking lot to get the fluid circulating and then drain and refill again. I doubt you'll have any issue.