My car is an 87 Formula with an LG4, 5spd. It has rear drums, and I believe it has 2.77 gears. The car is making alot of noise when coasting (seems to go away for the most part when I step on the gas), and it is definetly coming from the rear axle. It is a loud whirring at lower speeds, especially when coasting. But it becomes more of a deafening whirring/grinding with more speed, especially at 75+ mph, to the point where the car is vibrating through the driveshaft, transmission and shift stick so badly that I'm afraid it's going to shake the car apart. There is also some light clunking occasionally when the clutch is being engaged. Any idea what's causing this? Thanks,

Steve

 

Anybody have any ideas??

 

I would check the u joints and the drive shaft.

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I just had someone help me rebuild my 9-bolt 3.45 posi/disc rear end. I have the same noise. On coasting of decelleration there is noise. We suspect the ring & pinion aren't matched properly. I re-used the crush sleeve and used a .005" shim. We re-torques to get proper pre-load on the pinion bearing. Alsothe driveshaft is the 1LE aluminum and less than 5K miles on it. It has me stumped. I guess I need to have another shop diagnose and repair it. 8^( Don't ignore it, though. Good luck with yours, Lon.

 

Sounds like the pinion nut is loose...

Does the pinion seal leak? I'd bet money it does.

Take it somewhere, have them pull the driveshaft and tighten the nut(1¼" - requires air tools). Chances are it's loose because the pinion "head" bearing is wasted. Try that though, if it helps at least you know what you have to do, which is replace all the bearing in the unit. Make sure you keep fluid in it if it isn't already too late from the leaky pinion seal.

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"So many Mustangs, so little time..."

 

I have a similar problem running on my 3.4 auburn. I thought it was the axel bearings and replaced those to find the mystery noise came back after 50 miles. The really wierd things is the noise does not really come up until i mash the gas once, then it really starts this metal on metal sliding/griding/whirling kind of noise. I have taken the rear apart several times and everything seemed fine. Pretty sure i hitting the pinion and ring dead on and they were no noiticible signs of damage to any parts. The rear was built for autocross by the guy who owned it before me, so i am guesing it is something he did. well 87FormulaGuy i know that is not much help but I guess all I can say is I will let ya know whenever i figure it out. Could it be the Carier bearings(case bearings?)?

 

RB83L69, on our cars do you have to press those pinion bearing, which would also mean do I need a special tool to pull out the pinion and pinion yolk? I will go check it out later, just curious for now