hey all,
ive been hearing a clunk in my rearend area a lot lately especially whe i start the car in first gear and accelerate and sometimes when i decelerate. when it happens upon accleration it usually clunks in second gear. it has been more frequent lately so i had a look under the rear and saw a torn boot at the axle and diff and could see all sorts of grease slung everywhere. i suppose this could be why it creaks and moans every morning while i revers and switch gears and possibly why it slams into gear very hard sometimes. also i dont know if this is normal but when i shift gears it raises and lowers the rear of the car considerably and ive never noticed this with any other car ive owned with rear wheel drive. i found an axle reboot kit online for about 40 dollars wich could possibly be a cheap fix but i wonder if i should replace all the axle assemblies and do it right from the start. the axles seemed to range from the 2 - 3 hundred dollar range per side not including a 100 dollar core charge. i would love to take this to an indie and not worry about it but the one i have gone to in my area only wants to put dealer only parts on it so im sure that would make it a 1500 dollar job in no time , so i was wondering if there is a sure fire way to see if the axles definitlly need replacing at this point or if the reboot kit will suffice. as i am only 23 with a limited income, i would hate to spend a months salary on this job but then again i also worry about letting them deteriorate too badly and cause an accident or something. also id hate to spend a hundred bucks and a days labor on boots that wont solve my problem. i hope someone can shed some light on this and help me make the best decision to keep my car in good shape, thanks in advance

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual