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Lookin for info on pumpin out the diff

2K views 10 replies 7 participants last post by  Mr.Thunderbird 
#1 ·
Don't need to remove the rear cover, just want to pump out the fluid that's in the diff and replace with new. Anybody got a pic of the fill cap location? Never done an independent rear before, just need to know where to open to drain or pump out the lube that's in it now.
Replacing the lube with Royal Purple/Lucas mix with friction modifier. I have had good luck with this combination before and figure it would be a good substitute for regular gear oil in my 4.6 bird.
 
#2 ·
To make sure that any sludge and old oil gets out, I would really recommend pulling the back cover to drain the fluid.

Does your rear have a trac-lock?
 
#3 ·
Looking at the back cover, the fill hole is in the lower right corner with a plug. Use a wrench with a short extension to get it out.

Thunderstruck95 makes a excellent point, not too difficult to do.

Joe
 

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#4 ·
Don't know. It's a 4.6 but don't know much more than that. I'll look but I want this done. If the rear cover can be taken off easily then I'm in but if I need a lift or remove a lot of other items, I'll go with pumping. It's getting new gears soon, but I may put the gears off till next fall if this works well.
 
#5 ·
Just stick your head underneath the car and you will see for yourself how complex the job is (it isn't).

If you are going to do gears, I would hold off and do the proper clean at the same time since you are gonna have to take the cover off anyway.

You can do a proper clean while you are swapping gears (and by proper I mean take the cover off, pull the ring gear assembly), and spray the crap out of the inside with brake parts cleaner.

If you take a look at your rear diff under your car and immediately see how to do this job, just save up your cash, buy the gears, and pay someone do swap them in.
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Otherwise, just drain/pump the old fluid out and refill it. IIRC, that's probably a $10.

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Here are the URLs I collected before I redid my rear diff several years ago.

DIYs
Differential Gears - Installation Instructions | AmericanMuscle
8.8 Axle Gear Install
Free Automotive Differential Ring and Pinion Gear Installation Instructions - Drivetrain

Tbird Specific Tips
TCCoA Tech Articles
http://forums.tccoa.com/showthread.php?t=35362

Info
Differential Installation Instructions | West Coast Differentials
A Guide to Mustang Rear Gears | AmericanMuscle
 
#7 ·
Having just serviced my wife's GM again Advance Auto has Carquest Synthetic 75w-90 for ~$5 a quart. And changing the fluid is done easily with removing 10 bolts 13mm heads, some black RTV, gasket scraper and 3/8 square drive (extension works fine) for the plug. Longest part is getting the fluid back in.

Did a axle (on the GM) replacement today with new bearings and seals in 90mins. The center section on all 8.8s are the same.
 
#8 ·
The reason I asked if it had a trac-lock is because that would be the only reason to use a friction modifier/additive. If it's just an open diff then all you need is straight gear oil.
 
#9 ·
I was just getting ready to see if I needed to use the friction modifier with out track lock. Planning on doing oil change and gear lube today. Is there a tab or something that identifies this as a tracklok or not?? Also, not related to the rear end. I have noticed since I have had the car that the oil pressure drops to nothing while driving. Then when I hit a bump it jumps back to full pressure. When I slide the electric connector around on the oil pressure sensor, it seems to work ok for a while then eventually goes back to the On again off again routine. Anybody else ever see this?? I'm thinking of changing out the sensor to see if that will help.
 
#10 ·
No need to add friction modifier if it's not a trak-lok. With the car off the ground, spin one wheel. If the other wheel spins in the opposite direction, it's an open diff. Same direction, trak-lok.

Al
 
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