what is the cost for a automatic transmission AWD replaced,THANK'S

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my transmission don't change gears only 1,2 don't gears on 3,4,5 the codes are ok,im goint to replaced and i will like to know the cost,the AAMCO shop wants $2,800 to fix the tranny,i find on online one tranny with 37,000 miles for $1,000 so i will like to know, how much is the cost to replaced, an please let me know what is better fix it or replaced,thank you,,,miguel