Best rear end gear oil to use (75w90 or 75w140)
Hey guys, I have a 2006 Mustang GT with manual transmission. I had rear end work done a few days ago and ever since, it's groaning in the corners. I'm pretty sure they put 75w90 in the rear with one bottle of friction modifier. Doesn't sound like that was the best choice. Shouldn't I really be running something like Royal Purple 75w140 with at least a bottle of friction modifier? Especially since I now have 3:73 gears. I also don't know if my car has the updated clutch pack from Ford or not but I never had a problem with noise in the corners before (nearly 80,000 miles on the car).