5.0 Mustang & Super FordsHow To Drivetrain
2002 Ford Mustang GT 8.8 Rearend Rebuild - Rearend Revival
Sometimes Things That Go Clunk Can't Be Right
Horse Sense: While a 'Stangbanger's ultimate dream to have a super-modified car that remains absolutely perfect and free of bad noises forever, the truth is, horsepower and torque have a unique ability of finding the weak link in a Mustang. There's always a chance that a bad-noise-emitting problem could arise at some point, especially as more performance modifications are made.
Noises go hand-in-hand with the Mustang hobby. There are beautiful noises, such as the sounds that come from fine-tuned 'Stang engines at full scream on the chassis dyno or dragstrip. Then there are funny noises, like belt squeals, chassis creaks, dash rattles, and such. Finally, there are bad noises that are usually signs of serious problems with a Pony's engine or drivetrain, brought about by a lack of maintenance or an abundance of power.
Now before we go further with this report, we're not saying this to scare you or deter you from making moves that will put your Pony on the next plateau of performance. Rather, we encourage you to make those moves. As many of you know, making big steam is a favorite pastime for your tech editor and the crew at 5.0 Mustang & Super Fords. However, each time we increase the power output of the Ponies we work with, we're doing so with the understanding that we're taking the cars beyond the safe haven of stock.
With that said, bad noises are inevitable when you push closer and closer to the edge of the high-performance envelope. We've heard the sounds of catastrophic failure a few times now. We also understand that when parts do fail and you start hearing bad noises, sometimes you just have to charge the bad fortune to the game, identify the problem, make necessary repairs, and move on.
That's what we're doing with this tech effort-getting to the bottom of a disturbing hollow-sounding, clunk-type noise that's coming from the 8.8 rearend in our '02 Mustang GT. We first encountered the racket immediately after making our final pass at a dragstrip test session. Clunking and a severe vibration in the drivetrain (that increased and decreased with wheel speed) made their presence known during our drive back to our pit.
Right away, checks were made to isolate where the noise originated. After securing the 'Stang on four jackstands, we inspected the undercarriage to see if the noise actually was the result of the driveshaft making contact with the floorpan, torque arm or exhaust. After confirming that the shaft was OK, we checked out the differential (by engaging the transmission in First gear and turning the drivetrain) and found the noise was clearly coming from inside the 8.8.
As a general rule, if axles aren't broken and you're experiencing a bad noise from inside the 'Stang's rearend (but the car is still driveable, like ours), a broken ring or pinion gear, or a broken component in the differential usually is the source of the noise. With the malady requiring a more extensive investigation, we delivered the Mustang to GTR High Performance in Rancho Cucamonga, California, where technician Chris Balster found the source of our distressed diff's problem and performed the surgery that will make things right.
Photos of the search-and-rebuild process are telling, so we suggest you stay with this one and see what we've done to ward off future situations for our supercharged 'Stang's rearend.