Like the title says, i have a used set of 3.73's in my aod car an they whine like crazy at 65+ mph...they are quiet under 65.....i was hoping they would quiet down as they broke in, any chance? also would a fluid change help?
yep they were used...outta an explorer w/35K on it...i might just have to live with it till i put my 4r70w gearset in my aod...then i might change to 3.55's
used gears are sometimes really tough to get right,I spent a coupla days on a set of used 4:10s before I finally hit the sweet spot,many times running marking compound until I got the right pinion shim,I think with used gears it all depends how the were initially set up.
I think a lot of guys have trouble reading the pattern because the rear needs to be under a load when running the compound,if not the pattern will not spread out and give a clear mark,also the pinion nut needs to have the proper preload when reading the compound or the results will be different after the crush sleeve is installed and dialed in.When I read the compound I install the axles and drums and apply the emergency brake ever so lightly ,not even to the first click cause that will be too much,best if someone holds it a little,or you could adjust the brakes to apply the load needed,prolly around 50 ft lbs is all.some used gears may allways whine no matter what,IMO the coast and the drive pattern need to be pretty close to being centered from root to top,but you can get away with a little variance as I did with the 4"10s the drive side was a little low and the coast was a tad bit high but that was the best it could get,pinion depth will effect from root to top, backlash can effect it as well however only slightly.a pinion shim change of only .001 can have a substantial impact on pattern,thats why its sometimes hard to get em right,even if you have a good pinion depth tool,marking compound is allways the best,the tool will only get you in the ballpark, thus saving time.of course this is just MHO.
buying used gears are a hit and miss thing. I bought used 3.55's and I had no issues at all w/ them but you cant bank on that all of the time. Gears dont break in but they do develop a wear pattern wich is where some of your wine is comming from, the rest is prob do to not being installed within spec.