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Differential "flush"

Big6ft6

Well-Known Member
Joined
January 3, 2007
Messages
108
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1
City, State
Madison, WI
Year, Model & Trim Level
1997 5.0 AWD
I looked up how to do a differential flush, it said the following:
1) Drain diff fluid
2) fill diff fluid, drive 5-10 miles
3) Drain diff fluid
4) Refill

Someone said the differential fluid is $80...so this procedure, having to refill the diff twice, would cost $160 in fluid. Any thoughts/comments?
 



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I never heard of this procedure! Just let the fluid out and refill. If you need to do that buy the cheapest gear oil then refill with synthetic.
 






That seems crazy, every diff fluid change i have ever done, even on my fathers race car, was drain, and refill, on my Ex, i did make sure that all the old oil was out, i even wiped it up, but running new oil though it for only 15 miles, seems crazy, especially considering that you will have to add Friction Modifier, if you have the 8.8, which is $8 a bottle.
 






Waste of money, although differential lube is between $5-13 a quart (at most) and you'll use 3 quarts. Even with friction modifier, no way it'll cost $80.
 






That seems crazy, every diff fluid change i have ever done, even on my fathers race car, was drain, and refill, on my Ex, i did make sure that all the old oil was out, i even wiped it up, but running new oil though it for only 15 miles, seems crazy, especially considering that you will have to add Friction Modifier, if you have the 8.8, which is $8 a bottle.

Plus you would have to seal the diff cover to drive the 5-10 miles so it all didn't leak out then seal it yet agian after draing & re-filling.

The only place I could see where the procedure might be necesary is if on a Ford 9" or other rearends that don't have a removable diff cover.
 






Old spec was 75w90. Had too many failures so spec was changed to 75w140 full synthetic (supposed lifetime). Most stores $12-15 per quart for generics, $20-25 for royal purple. You need 3 1/2 quarts + a $6 tube of friction modifer if you got a limited slip. You can get 85w140 non-synthetic for $12-20 per gallon depending on brand. Little bit thicker so gas milage might be less in cold weather but not going to hurt anything. Will need to be changed every 40-50k miles.
 






Multiple dittos here. A diffy "flush" is unnecessary, wasteful, and would be a PITA.
Remove the cover, drain, clean thoroughly, reseal, and fill. Don't burn time and money.
 






Awesome. So is the friction modifier a Ford specific product? Where do I get it? I've only had mechanical limited slips before...just used lube without any additive.
 






Awesome. So is the friction modifier a Ford specific product? Where do I get it? I've only had mechanical limited slips before...just used lube without any additive.

Ford dealer. Some autoparts stores may have it as well.
 


















Give your local Autozone a call. Usually has the generic in stock. Comes in a green and white tube for $6.
 






Synthetic I used already had friction modifer in it. Mobil 1 I believe - from Advance Auto Parts.
 












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