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Discussion Starter #1
ok im to lazy to search so if already posted flame away.

96 bronco, w/ limited slip i believe.

drained fluid about 2qts

told to refill to just under fill hole.
took 3.75 quarts.

now when i drive on acceleration makes whinning noise. at coast very quite.

any info thanks adam
 

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Satyr of the Midwest
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Did you also add the special friction modifier additive with the oil? If not, you're frying your limited slip clutches and discs.
 

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Discussion Starter #3
no i was told by the shop it was not necessary. i am getting the impression that it is. will it damage the clutch's to drive aprox 15-20 miles
 

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Satyr of the Midwest
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Meh, you're probably all right. Go to a Ford dealer on Monday for some, and put it in ASAP. I'd never listen to that shop for any advice again though.
 

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Where is this shop you took it to? Sounds like you're getting auto advice from a 6 year old.
 

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Had the same problem for a month with my limited slip. As the previous posters have said, add the friction modifier. It is like $5bucks for 4 ounces. You can buy it from any reputable parts store like O'riellys or NAPA. The Ford dealer is as cheap as any but do not let them put it in for you because they will charge an arm and a leg to do it.
After you put the friction modifier in drive it a few days to see if noise goes away. If not, put another 4 ounces in and that should do the trick.
 

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It's BTW Not AKA!
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If you dont know for sure you have limited slip, I would look at determining that first. No sense in adding the FM if it will do no good.
 

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On the back of the rear differential, you should see a metal tag held in place by one of the differential bolts if you have a limited slip. It should have an L or an L-S in the number if you have a limited slip. There is also a way to determine by looking at the numbers on the door jamb but I can't find the info on that right now.
 

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Former owner of Shadofax
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On the back of the rear differential, you should see a metal tag held in place by one of the differential bolts if you have a limited slip. It should have an L or an L-S in the number if you have a limited slip. There is also a way to determine by looking at the numbers on the door jamb but I can't find the info on that right now.
or if he just had the cover open to drain the fluid, he could have looked, this way you know for sure, as long as you know what an LSD looks like.
 

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Thanks for the info. I changed my rear diff fluid before i had to park my bronco but i never knew about that Friction Modifier. :banghead I will Have to put some in before i start driving it again.
 

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Satyr of the Midwest
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:rolleyes:

I use Mobil1 75W-90 synthetic gear lube in both differentials, and I still add the friction modifier. I'd trust Ford to know what their gears require over any lube company. Even if he doesn't have a limited-slip differential, the friction modifier can't hurt anything. I'd rather have him spend the $5 and be wrong than say forget it and burn up the clutches.

Oh, don't forget: you're going to have to lose a little oil in order to get enough friction modifier in there. If you have a suction gun, you won't even have to pop the cover off. :thumbup
 

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Ford Hoarder
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Door tag should have a letter in front of the axle code if its a limited slip, assuming it hasn't been changed. Mine has a H9 (3.55 LS)
Also You can buy oil with modifier in it already, I got some Royal Purple to do mine when it warms up.
 

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I refilled my differential with the royal purple and it still made the noise until I spent $5 bucks for four ounces of friction modifer.
 

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So the friction modifier makes it so the clutches slip on road? I think maybe I'm just confused about what it does and why it does not affect off-road driving too.
 

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how much friction modifier to add?

This seems as good a place as any to add a question I've always had about the friction modifier.... Everybody sells the 4oz size. Ive read multiple threads on this forum about how much gear lube a 9in rear end takes. And seen everything from 2.5 quarts to almost double that, to the ever popular "until its full". I'm a proponent of the "until its full" method, insuring the truck is level, and knowing that the differential angle has been corrected for the lift. All that being said, my 9in does seem to take about almost 5 full quarts to be just below the fill hole. Should I be adding more friction modifier, if the 4oz bottle is the right amount for 3 quarts? I would imagine that we are looking for the correct ration of gear lube to modifier, not just "some is enough, but there's no such thing as too much?"
Next time I will be looking for the pre-mixed, or "modifier unnecessary" version.
 

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Former owner of Shadofax
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This seems as good a place as any to add a question I've always had about the friction modifier.... Everybody sells the 4oz size. Ive read multiple threads on this forum about how much gear lube a 9in rear end takes. And seen everything from 2.5 quarts to almost double that, to the ever popular "until its full". I'm a proponent of the "until its full" method, insuring the truck is level, and knowing that the differential angle has been corrected for the lift. All that being said, my 9in does seem to take about almost 5 full quarts to be just below the fill hole. Should I be adding more friction modifier, if the 4oz bottle is the right amount for 3 quarts? I would imagine that we are looking for the correct ration of gear lube to modifier, not just "some is enough, but there's no such thing as too much?"
Next time I will be looking for the pre-mixed, or "modifier unnecessary" version.
I don't see how that is anywhere near possible....almost 5 qts. That is more than 1 gallon.

What you may have read on here could be someone stating larger quantities 1) because they have an after market cover that provides increased fluid capacity, or 2) a cover with a raised hole. Different types of differentials might account for some variance in amount of fluid capacity.

there is no need for that amount of fluid...just a few other examples for you:

my '78 D44 front I just drained and it was about 2qts, and my rear fullfloat D60 took about 3qts to refill to the bottom of the hole.

Now, my manual says that "service refill capacities are determined by filling:"
"front axle, to the bottom of the filler hole"
"rear axle, to between 1/4"-9/16ths below bottom of filler hole."

It does give the apx. capacity each should take:
front 3.8 pints= 1.9qts.
rear 5.5 pints (8.8 axle) = 2.75 qts, which seems about right since my D60 takes a bit more.

overfilling or underfilling is not good in either case.

I checked a couple sites for 9" fluid capacity and ended up with fordtruck saying close to 6 pints (little under 3 quarts), and another site showing 10.25 as apx. 3.75 qts with stock cover.

so to answer your question you should be using 4oz of the fric. mod. for what should be going in your axle, which is a little under 3 quarts for the 8.8 and 9.
 

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Even without the large rear cover I have, the larger the lift, the more the pinion points up. This means the fill is higher (in the case of a 6" lift, that is a few inches higher). I have always filled until full, and I use 4 quarts with a larger AL cover and 4" blocks (that is a different thread. I know, I know, I know. I still did, but I know...). How does one account for this raised fill hole? Does anyone here account for it?
 

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Former owner of Shadofax
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Even without the large rear cover I have, the larger the lift, the more the pinion points up. This means the fill is higher (in the case of a 6" lift, that is a few inches higher). I have always filled until full, and I use 4 quarts with a larger AL cover and 4" blocks (that is a different thread. I know, I know, I know. I still did, but I know...). How does one account for this raised fill hole? Does anyone here account for it?
I account for it, if it's higher up, you need to be looking at where, on a horizontal plane, was that fill hole in relation to the bottom of the axle tube? Cuz if it was right down at the bottom of the tube, and now it's say an inch or whatever above....guess what, you've now begun to fill your axle tubes with gear oil. I would suspect that the outer seals were meant to receive some tube flow down from time to time, but were never meant to be semi-immersed in the gear oil.

This is also the likely culprit for anyone that has had an issue with blowing gear oil out of their tube breather after lifting the rear for a 6" lift.
 
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