vibration durring coasting

hipo50mustang · May 14, 2008

ok, a few weeks ago i swaped out my gears to 3.73. now I have a vibration only durring coast. when I accelerate, everything is fine. I just ripped out the rear end today and tomorrow I am taking the diff out to check the shims and spacing.
what, exactly, should I check so I wont have to do this a third time?? :wall:
Thanks,
Mac

CC'S95GT · May 15, 2008

ch your u joints on the drive shaft

hipo50mustang · May 15, 2008

the u-joints and driveshaft are fine. i checked those before ripping out the whole rear end again.
anything else?

CC'S95GT · May 15, 2008

were the gears new or used , i'm thinking the same as you , maybe axle clips IDK

hipo50mustang · May 16, 2008

new ring and pinion,
finally got the diff back in, I think it was the pinnion depth was too shallow, not enough shims. I remeasured the orriginal pinnion depth again and it was off alot. then i readjusted the back lash to within spec,
now I just have to get the rear end back under the stang.
will let ya'll know when she is back on all 4's again. should be tonight if the weather hold out.

wayne94mustang · May 16, 2008

my car did this and it ended up being the u-joints....they dont have to have play to be bad

mine were tight as new but some joints have a plastic disc in the end of the cap and mine were tore up and hunks were in the brearings

hipo50mustang · May 16, 2008

well, it is all put back together and the vibration is gone, but now there is a whine. i think i put a little bit too much torque on the preload on the pinion, but I can fix that.
I am going to check the ujoints while I am at it also.
Thanks for the input.

wayne94mustang · May 16, 2008

how much preload did you set it at?

i like 25-30 ftlbs of rolling risistance (i cant spell) with new bearings....this is what my papers call for anyway and i have done 20 or so 8.8 rears

hipo50mustang · May 16, 2008

do you mean in/lb not ft/lb? because it should be somewhere between 8 in/lb and 24 in/lb depending on what source you read it from.
I have no idea because none of my torque wrenches go down that low to check, so I used my well calibrated breaker bar and stopped torquing when it felt right, which i know now is definately NOT RIGHT!! :wall: :wall:
taking it to a place with a lift so I wont have to take the whole damn rear end out again.

CC'S95GT · May 16, 2008

8 in/lbs is a bit more than finger tight

wayne94mustang · May 17, 2008

yeah sorry....inch pounds

i have a inch pound torque wrench that works real well for this

hipo50mustang · May 17, 2008

well, i am 98% that it is the excess preload that is causing the whining. but i dont have the time to take it all apart again. woulld be alot easier if I had access to a lift. so I am taking it to a shop next week. :crying: i know the pinion depth and backlash are correct now, just the damn preload.