Hey guys I was thinking of changing out the stock fluid in the rear end. Which one do u guys recommend. The best performing and the quietest. Another question also when I change the fluid do I have to put in another 4 oz of the friction modifier? Thanks
Need some help with Rear diff fluid???
- Thread starter ryan.garcia2733
- Start date
If you have gear noise that is driving you crazy, and you want to quiet the gears, Red Line Heavy Shockproof.
If you do not have gear whine, Amsoil Severe Gear 75W-140
and friction modifier
Amsoil Slip Lock - don't use in Torsen diffs.
3 quarts of diff fluid + 1 bottle of friction modifier. I recommend testing the car with no modifier. If you hear chattering around slow speed corners, pour in 2 ounces, then test again. 2 ounces may take care of it. If it doesn't, use the other half bottle.
Rear end should be a 2.5 quart fill.
If you do not have gear whine, Amsoil Severe Gear 75W-140
and friction modifier
Amsoil Slip Lock - don't use in Torsen diffs.
3 quarts of diff fluid + 1 bottle of friction modifier. I recommend testing the car with no modifier. If you hear chattering around slow speed corners, pour in 2 ounces, then test again. 2 ounces may take care of it. If it doesn't, use the other half bottle.
Rear end should be a 2.5 quart fill.
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I'm getting crazy gear whine that is driving me crazy I hear it over the radio. And I don't have a Torsten diff so I put 2.5 quarts of the redline fluid and test it out. If it makes noise throw in two ounces of friction modifier? Let me know if I missed anything. Thanks again!
So, I orignally put in redline lightweight shockproof and a bottle of friction modifier from o'riellys. My mistake, the stuff was garbage, the FM not the redline. I since then have put int heavyweight and Ford X3 FM which is like $6 at the Ford Dealerships. Awesome combo. I didn't really have any whining, but the rear end is so smooth and drives so perfect.
the Amsoil FM might be good, but read a lot on the ford rear diffs and one thing I have always noticed, nothing beats the Ford FM for their diffs. Also, I put in the lightweight schock proof initially without FM and got chatter out the ass after about 3 days. the generic stuff helped a little, but not enough, and the Ford stuff cleaned up the chatter instantly.
Honestly I think your crazy to not just put the whole bottle in. It is what Ford calls for, so why do less?
EDIT: I only wanted to add, I am not sure how the redline heavy weight will be during the colder months, so before we start getting cold out I'll probably pick up 3 bottles of lightweight gear oil just incase the diff acts real stiff so I can swap it out. Unless someone wants to chime in and say how it has been. I was recommended redline by Jason at Hypermotive and he hasn't steered me wrong yet.
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Did light shockproof quiet your gears as much as heavy shockproof?
If you have a torsen do not use friction modifier, which is for clutched rears.
nope, made the rear smoother than the Royal Purple I had, but def not as quiet as the heavyweight. Thought honestly my gear whine wasn't bad infact I didn't really think I had any, but I didn't realize I did until I put the heavyweight in. That rear is so quiet now.
I've been in cars with the really loud 3.73 gear whine and mine just has never been that bad. So I would assume that someone with really bad whine, the lightweight would be pointless other than for a smooth differential.
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My rear with the stock cover wouldn't even hold two full quarts with the friction modifier added. I just threw so RP in it since I was about to leave on a road trip, and it was readily available.
So wait I'm confused how much exactly of this stuff do I need to do the swap. I know the 4 oz. of the FM but Howard quarts does the stock rear take!!! I hear 2.5 and then I hear 2 not sure which.
partially will depend on how well you drain it. Dead empty I believe it is about 2.5 but that is assuming you pull it all out the bottom and such when you empty it.
Have you noticed any fuel economy decrease using Heavy Shockproof? I don't think I lost any mpg using it in my GT500.
Depending on the differential cover used or how empty the pumpkin is, some owners are reporting that 2 quarts wasn't enough fluid. I recommend buying 3 quarts "just in case". It's better to have more than you need than not enough. In my 2008 GT and 2009 GT500, 2 quarts + friction modifier were more than sufficient. I even spilled some on the ground, still having enough. Both cars had the rear diff cover fully removed, all fluid was drained.
When I change the fluid in my 2014 GT, I will report how many quarts it took. However, since I will likely change the rear cover, more will be required.
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RL Heavy Shockproof is insurance in a dragstrip car on slicks. It will quiet SOME noises but won't do a lot for gear whine.
I do run slicks and pound my car at the track on street legal nights so, I wanted protection. RL HD sticks like mad to everything but, no fuel economy changes noted.
It needs between 2-4 oz of FORD fm, just like any other standard gear oil. I put in 2 first and if it starts making noises, I add the other 2. it may take a couple days for the noises to start so be patient.
I do run slicks and pound my car at the track on street legal nights so, I wanted protection. RL HD sticks like mad to everything but, no fuel economy changes noted.
It needs between 2-4 oz of FORD fm, just like any other standard gear oil. I put in 2 first and if it starts making noises, I add the other 2. it may take a couple days for the noises to start so be patient.
Nope, MPG are the same, I have noticed and it just is weird and I am getting used too a slight drag type feeling from the rear. Kinda hard to explain but kind of like there is more friction from the fluid and while I would normally coast it does a mild "engine" break type feel. Doesn't bother me other than I just had to adjust my driving a little.
your right, i forgot about this. Mine took almost all 3 quarts + FM with the Boss 302 take off cover i got from Jason at hypermotive off his Boss 302. Same one that comes on the track pack.
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I'm doing this soon. I have 3 quarts of Redline HSP. Should I pick up a cheap hand pump or is there enough room with the rear axle sagging to funnel and pour?
If you have the stock/cheap cover for the diff that means you fill it from the rear(front of the axle), somewhat next to the driveshaft/pinion yolk. You are not getting a funnel in there.
I picked up a $10 hand pump at o'riellys when I did mine. Took all of 60 seconds to pump all the oil into the diff.
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I used a hose over the nozzle on a RP squeeze bottle and filled from the front hole. That worked, but I had a hand pump just in case.
good info, thanks guys
track pack yes but with the Boss it doesn't come standard. Is an addon option.
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