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rear diff fluid

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Old Jul 23, 2007 | 07:15 PM
  #1  
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rear diff fluid

i recently replaced the fluid in he rear end, i put in mobil1 synth 75w-140. do i need the modifier with the synth?
 
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Old Jul 23, 2007 | 07:33 PM
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If you have limited slip diff, I believe you do. I understand that even motorcraft factory diff oil used for expeditions is synth, so using mobil 1 synth would not negate the need for it.
 
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Old Jul 23, 2007 | 07:57 PM
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i'll get some. do you think there is any damage done after driving 300 miles? I pulled a 5000lbs trailer some too. oops i guess.
 
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Old Jul 23, 2007 | 08:32 PM
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Hopefully not. It's suppose to prevent diff clutch chatter. I'm reading the book about the theory of operation, and the clutch works/compensates when one tire is slipping. I hope you didn't tow off road or in slippery condition

You're good, just get a bottle as soon as you can and put it in there. This is a dealer only item, I believe. That's where I got mine.

By the way, while you're under your truck, it may be worthwhile to check the vent tube on top of the diffrential shaft if you have one, I found mine on the driver side.

Somebody posted here that it got clogged, possibly causing rear wheel seal leak.
 
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Old Jul 23, 2007 | 09:01 PM
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thanks i'll check it out. I had it on the road the whole time. so i hope to get it done tomorrow night. We have 2 more fights this truck week and this has to pull the ring. it's about 5500lbs.
 
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Old Jul 24, 2007 | 06:07 AM
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royal purple has it in it already and ends up a little cheaper then buying mobil1 and the syncromesh....thats what I put in my 01 cobra.
 
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Old Jul 24, 2007 | 07:23 PM
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I Got It In. That Stuff Stinks. Thanks Yall
 
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Old Jul 25, 2007 | 12:06 PM
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Originally Posted by wrenchturner
I Got It In. That Stuff Stinks. Thanks Yall
Question - did you first check your axle code to check your gear oil requirements?

-You only needed to do what you did if you have limited slip

-If you DO NOT have limited slip, your gear oil is too heavy of a weight.
 
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Old Jul 25, 2007 | 04:50 PM
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yeah i have a LS. It's on an FX4. H6 axle code 3.73 LS. I like this ratio alot since I've been pulling a trailer. Has anyone had issue with the rear axle? This is my first IRS.
 

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Old Sep 19, 2007 | 09:39 PM
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Ford specifies 75w140 synth in both open and limited slip diffs, front and rear axles through out the light truck line through super duty. It is also the in service replacement for FHLP gear oil found in earlier models.
 
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Old Sep 20, 2007 | 10:23 AM
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Originally Posted by cleetis
Ford specifies 75w140 synth in both open and limited slip diffs, front and rear axles through out the light truck line through super duty. It is also the in service replacement for FHLP gear oil found in earlier models.
That's not what my manual says for my 2002 Super Duty. Front axle is spec'd at 75W-90 for the Dana 50/60. Only the F250/F350 SRW are spec'd at 75W-140 synthetic for the Sterling 10.50 rear axle. The Dana 80 (F350 DRW/F450) are spec'd at 75W-90 synthetic and the Dana 135 (F550) is spec'd at 80W-90.

Just a few variations, but still noteworthy.
 
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Old Sep 20, 2007 | 11:37 AM
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I had my seals done at the beginning of summer and I am not sure if they put friction modifier in when they changed the fluid. Is there any way to tell? symptoms? It is an 03 XLT with 3:73 LS. I am a little concerned now.

R
 
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Old Sep 20, 2007 | 11:10 PM
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If only ford could build F150 and expedition axles as well as the super dutys. I go through so much 75w140 on those with there leaking seals. dont rember the last super duty that had any axle work done other then the std. brake job. forget that they do vary there oil weights. when in doubt check your axle tags.
 
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Old Sep 21, 2007 | 06:48 AM
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Exclamation

Originally Posted by racerock
Question - did you first check your axle code to check your gear oil requirements?

-You only needed to do what you did if you have limited slip

-If you DO NOT have limited slip, your gear oil is too heavy of a weight.
Both types of rear differentials use 75W-140, GL-5 oil. It must be synthetic and the controlled slip model must have friction modifier added.
 
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Old Sep 21, 2007 | 06:49 AM
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Originally Posted by Rentaltux
I had my seals done at the beginning of summer and I am not sure if they put friction modifier in when they changed the fluid. Is there any way to tell? symptoms? It is an 03 XLT with 3:73 LS. I am a little concerned now.

R
Check your work order slip and see if it's listed.
 
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