msbmustang Posted February 20, 2016 Report Share Posted February 20, 2016 I have been having some vibrations and noise coming from the back end of the car. At 145000 miles I was just wondering how long a rear differential will last? Also it is better to rebuild it or just buy a new one? Thanks, MSB Mustang, Mark Quote Link to comment Share on other sites More sharing options...
shel-b001 Posted February 21, 2016 Report Share Posted February 21, 2016 (edited) A rear end should last forever ,but that being said you can have problems with the bearings . sounds like maybe a pinion bearing which can be replaced. Edited February 21, 2016 by shelby001 Quote Link to comment Share on other sites More sharing options...
ilmor Posted February 21, 2016 Report Share Posted February 21, 2016 The rear axle should be the only thing remaining from the car at some point in time. Quote Link to comment Share on other sites More sharing options...
msbmustang Posted February 21, 2016 Author Report Share Posted February 21, 2016 So it sounds like even though I am at 145K miles the rear dif should still be OK! Of course most of those miles are "less wear and tear freeway miles" driving 50 miles each way to work. New tires next then... Quote Link to comment Share on other sites More sharing options...
shel-b001 Posted February 21, 2016 Report Share Posted February 21, 2016 So it sounds like even though I am at 145K miles the rear dif should still be OK! Of course most of those miles are "less wear and tear freeway miles" driving 50 miles each way to work. New tires next then... Just maybe you need to change the fluid & install some new friction modifier, these 8" posi`s are pretty tough. Quote Link to comment Share on other sites More sharing options...
AKSHELBY Posted February 21, 2016 Report Share Posted February 21, 2016 could also be a u-joint... they are usually about $20-30 bucks....may be you will get lucky and it will be a cheap fix....I know sometimes Ford uses "lubed for life" joints ......HA HA Quote Link to comment Share on other sites More sharing options...
msb64 Posted February 21, 2016 Report Share Posted February 21, 2016 Check the rear tires, and don't forget the tpms sensors, it is possible that one of the tpms bands came loose. In any case, a fluid change in the rear is not a bad idea with that kind of mileage, and it also gives you a good excuse to install one of these: Shelby version http://www.shelbystore.com/Shelby-American-8-8-Axle-Cover-2005-2013-p/7106s.htm Ford Racing version http://www.cjponyparts.com/ford-racing-differential-girdle-cover-kit-low-profile-8-8-1986-2014/p/M4033G2/ I always try to turn a repair into an upgrade, it makes the repair more appealing. Quote Link to comment Share on other sites More sharing options...
msbmustang Posted February 22, 2016 Author Report Share Posted February 22, 2016 Thanks everyone for the suggestions! I am going to do the fluid change and I was already going to dump my Nitto tires and go with Contenential Extreme DW's. I will report back if either of those items fixes the rear vibration problems. Also AKShelbyI did put in a new "one piece 1000HP AL driveshaft" a few years ago so the U-Joints are fairly new, i.e. less than 15K miles. Lastly MSB64 do the new rear covers acutually effect how the rear of the car feels? I also agree that repairs are a great excuse to do upgrades. Mark/MSB Mustang Quote Link to comment Share on other sites More sharing options...
msb64 Posted February 22, 2016 Report Share Posted February 22, 2016 Mark, the covers will not make a difference in the feel at all, so not in any way a direct solution to your original issue. Those covers/girdles do offer drain and filler holes at the rear though, plus they add to the overall strength of the rear end, with adjusters that support the main caps. They also come with premium grade gaskets and fasteners. You will need to remove the original cover and change the gasket anyways to drain the fluid, so that is why I suggested the upgrade. If you can, put your car up on a hoist and carefully inspect all the upper and lower control arms, bushings, brackets, bolts etc. Of all the oem pieces on the rear of the car, the weakest bracket is probably the upper control arm bracket, as it is a single piece of relatively thin stamped steel. The oem rubber bushings with that torque load and mileage are also a concern, inspect them carefully. It can be done on the ground with jack stands, but it is a lot easier to check everything on a hoist. Quote Link to comment Share on other sites More sharing options...
Robert M Posted February 28, 2016 Report Share Posted February 28, 2016 (edited) So it sounds like even though I am at 145K miles the rear dif should still be OK! Of course most of those miles are "less wear and tear freeway miles" driving 50 miles each way to work. New tires next then... If you have 145,000 miles on your GT500 and you feel that the differential may need attention, the CF clutches will not last forever. Next time you change your axle lubricant take your hand and dip out the sump area of your 8.8, it will most likely have an amount of black graphite sludge in the bottom. <<That is all wear from the CF clutch packs in the posi unit. At 600 original miles I changed my original fluid when I de-rusted/restored my 2008 8.8, I was amazed how much graphite sludge was in the sump area of my 8.8. This sump area does not drain with a simple cover removal and fluid change, it requires digging down in the housing with your hand and wiping everything out with a rag, then re-filling the housing to the correct level. <<If this is not done at a fluid change, all of the "sump" contamination will recirculate through all bearings in the axle and clutches in the posi unit along with the new fluid that was added. Even in the "old days", the clutch packs required attention/replacement in the 8", 9", 10 bolts, 12 bolts etc. If you have 145K miles, there is going to be some wear on those original GT500 CF clutch plates. No amount of friction modifier is going to fix "lack of friction surface". <<If your posi unit is getting to that point. ^^^^^If your car had 14.5K, this would not be something to think about, but 145K, that is well beyond the miles of most GT500's that I am aware of...........and those clutch plates do not last forever. R Edited February 28, 2016 by Robert M Quote Link to comment Share on other sites More sharing options...
msbmustang Posted March 10, 2016 Author Report Share Posted March 10, 2016 Sounds like it is time for a rear diff "Rebuild" project. How difficult is it? MSBMustang / Mark Quote Link to comment Share on other sites More sharing options...
Robert M Posted March 13, 2016 Report Share Posted March 13, 2016 (edited) Sounds like it is time for a rear diff "Rebuild" project. How difficult is it? MSBMustang / Mark Me personally, even though my car only had 600 original miles on it when I removed my complete 8.8 axle housing for a de-rust and restoration to correct assy. line specs, I had a local shop reuse the 3.73's that were installed when my car went through the Mod Shop, but had the oem CF posi unit replaced with an Eaton True Trac. The True Trac does not have the clutch packs and provides a smooth seamless transition from normal driving, turning etc. to positive traction locking when needed. I have been quite happy with it and it is always quiet. Here is an exploded view of the True Trac.............. There are also quite a few guys who drag race their cars and have this posi unit. Real big HP and slicks may end the True Trac life early, but many guys have had great success even at the drag strip. Before I took anything apart, I would first have the exact issue verified, and with 145K miles, there "may" be wear on most everything in that housing, depending upon past maint. practices? I believe FRPP offers a complete 8.8 axle assy. with 3.73 gears for $1000? or something like that. <<That unit would have the same CF posi unit as oem GT500. I would guess that "if" you chose to rebuild your 8.8 and keep your original housing, buy the time you buy the Eaton TT for $450 or so, and the gears, the large bearing rebuild kit including all bearings, seals and gasket and the fluid (friction modifier will not be required with the True Trac) $400 or so, and then also the labor to put it all together $200 or so...........This would be in the $1000 range also? If your axle has been maintained during the 145K miles, "possibly" your gear set "may" be reusable, but that is a lot of miles to rely on a 145K gear set to be quiet after a disassembly and re-assembly. <<Just my opinion. If you chose to go the complete 8.8 replacement route, there would probably be shipping costs to also take into consideration? and then who is going to install it and that possible cost? R Edited March 13, 2016 by Robert M Quote Link to comment Share on other sites More sharing options...
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