Rearend
Thread Starter
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Senior User
Joined: Jul 2006
Posts: 406
Likes: 0
From: Haysville Ks.
Rearend
Hey guys I went to a track last night and got to see what my truck would
do and it wasn't good. I only got 1 tire to going and I spun it 1/4 of the
way down the track till it finally grabed and then she took off. My time
was a 19.6367 at 84.76mph. The dodge I went against did 16.6519 at
81.04mph. Will changing the rearend fluid to some royal purple with the
friction modifier help to make it kick in or is it something else? I have
77,500 on it and I bought it with 50,000 and I don't know if the previous
owner had changed it. I know it needs changed but if I need to change
something else I only want to be in there one time because funds are a
little short right now.
do and it wasn't good. I only got 1 tire to going and I spun it 1/4 of the
way down the track till it finally grabed and then she took off. My time
was a 19.6367 at 84.76mph. The dodge I went against did 16.6519 at
81.04mph. Will changing the rearend fluid to some royal purple with the
friction modifier help to make it kick in or is it something else? I have
77,500 on it and I bought it with 50,000 and I don't know if the previous
owner had changed it. I know it needs changed but if I need to change
something else I only want to be in there one time because funds are a
little short right now.
Elder User
Joined: May 2008
Posts: 860
Likes: 2
From: Liberty Lake, WA
Do you know if yours is a limit slip? Not all of them came with one..
There is a tag on the rear end. You should see something with L/S on it.
If not, then get a Eaton True Trac. They work very well
There is a tag on the rear end. You should see something with L/S on it.
If not, then get a Eaton True Trac. They work very well
Post Fiend
Joined: Feb 2007
Posts: 14,541
Likes: 2
From: Dallas-Ft. Worth
Too much friction modifier will make it act more like an open diff if it is limited slip. I put royal purple in mine and so far so good. I haven't tried taking off with it to see if it spins both just yet... Might have to try that today. 
Hotshot
Joined: Jan 2002
Posts: 17,988
Likes: 207
From: La La Land
6.9 pints, (or 3-1/2 qts) 75W-140 SYNTHETIC gear oil.
If you have a limited slip rear differential you also need 8 ounces of "Additive Friction Modifier C8AZ-19B546-A" from Ford.
Pop
If you have a limited slip rear differential you also need 8 ounces of "Additive Friction Modifier C8AZ-19B546-A" from Ford.
Pop
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Cargo Master
Joined: Oct 2008
Posts: 3,330
Likes: 13
From: Eaton, CO
With a LS rear end you have to use the fully synthetic 75W-140 gear oil. The only stuff I could find already had that the slip additive in it. I bought a 4oz bottle of slip additive from Ford just in case.
I couldn't get the claimed 3.5 quarts of gear oil in the rear diff when I filled it the first time. After I drove it and everything got warm, I was able to fit the remaining 1/2 quart. I had to add a little slip additive. I still have to add a little bit more.
I couldn't get the claimed 3.5 quarts of gear oil in the rear diff when I filled it the first time. After I drove it and everything got warm, I was able to fit the remaining 1/2 quart. I had to add a little slip additive. I still have to add a little bit more.
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Thread Starter
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Senior User
Joined: Jul 2006
Posts: 406
Likes: 0
From: Haysville Ks.
Thanks for the help guys. I have been trying to find royal purple 75w-140 around here
but no body has it. Anybody use mobile 1? Does it already have the friction modifier in
it? I wondered if the clutches were bad but would a fluid change make a difference and
it start to work again?
but no body has it. Anybody use mobile 1? Does it already have the friction modifier in
it? I wondered if the clutches were bad but would a fluid change make a difference and
it start to work again?
Thread Starter
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Senior User
Joined: Jul 2006
Posts: 406
Likes: 0
From: Haysville Ks.
Well I did a fluid change on monday night and this afternoon I got both tires to hook
up. Just wanted to put a post up that the fluid did do the job. Thanks for the help once
again.
up. Just wanted to put a post up that the fluid did do the job. Thanks for the help once
again.
Rather Be Floatin
Joined: Oct 2005
Posts: 2,468
Likes: 0
From: Marble Falls, Tx.
Damn now I have worn out fluid!! Looks like I need to get me 4 qts. Royal Purple. Am I correct that I dont need the friction modifier with the royal purple. Sorry about the hijack!