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Diff fluid change ?'s

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chev4life

1/2 ton status
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Need to change fluid on my 14bolt w/detroit locker...what is a good weight and brand to go for? Also...should I use a paper gasket or a liquid gasket? Would black gasket goo work?
 
How often do you run water or mud? If not often I would recommend what I use. I run Redline Heavy Shockproof gear oil. It is not cheap like dyno oil but it is a full synthetic and is very good stuff. It is roughly a 75W-250. I use RTV for gaskets on differentials. Seems to work fine for me.

Harley
 
I would only use synthetic gear oil if you keep it out of the mud and water. It only costs a couple extra dollars for synthetic over dyno oil. It will keep the gears cooler and break down slower than dyno oil, and in an area like a rearend that is almost always neglegted, an oil that can resist breakdown and wear the longest should be used IMHO.

I use both the paper gaskets and high tack RTV.
 
I like the mud and the water, but would like to put synthetic in. I talked to a detroit locker guy at SEMA this year and recommended not running synthetic on the lockers...has anyone ever heard this? What weight do I run if its not synthetic?
 
chev4life said:
I like the mud and the water, but would like to put synthetic in. I talked to a detroit locker guy at SEMA this year and recommended not running synthetic on the lockers...has anyone ever heard this? What weight do I run if its not synthetic?
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For dyno oil I would use 85w140, or 80-90. For synthetic I used Mobile 1 syn. 75w-90 in my D70. I would have prefered a little heavier oil but got it for free so I can't complain.
 
My rear axle is welded so that isn't an issue with my synthetic fluid. My lockright has been in synthetic fluid for the 3 years I have had it and for awhile when the previous owner ran it.

Lots of people complain that there lockright is loud, but I have never heard a sound from my lockright with my thick synthetic fluid that I run.

Harley
 
I am running open diffs, but I used Mobile 1 synthetic - 75w-90 - per the recommendation of many members. I also used an original GM gasket with a very thin coat of RTV in the rear and just RTV in the front. Takes about two gallons to do both axles.
 
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I use Valvoline 80W/90 but I dont travel at high speeds or loaded, if it was a highway/tow rig I'd use synthetic :thumb:
 
I also run Redline , on Harley's reccomendation , for 4 months now with no problems . It likes to stick to everything , which is good . I swapped axles from my 3.08's to my 3.73's , whole housings , and when I went to roll the project truck which has teh old axles now , the damn thing still has a pretty good coating of Redline on it , and no surface rust from the morning dew :D
 
So I will see if I my parts store has a gasket if not I will just use RTV. How high much do you usually put in when refilling? I have a 14FF and dana 44 that I will be doing. I will also see what my parts store has in terms of fluid, I am a big fan of modil 1 from my SS so maybe I will go that route.
 
chev4life said:
So I will see if I my parts store has a gasket if not I will just use RTV. How high much do you usually put in when refilling? I have a 14FF and dana 44 that I will be doing. I will also see what my parts store has in terms of fluid, I am a big fan of modil 1 from my SS so maybe I will go that route.
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I don't really remember how much the 14's hold but I just changed the oil in my D70 and it seemed to hold about 6 quarts, hard to tell because I was using a hand pump and a 5 gallon bucket. THere is a plug in the side of the diff, on the pass. side IIRC. Get it out with your 3/8" ratchet and fill through that hole until oil starts to spill out the bottom of your plug hole.
 
bigyellowjimmy said:
I use Valvoline 80W/90 but I dont travel at high speeds or loaded, if it was a highway/tow rig I'd use synthetic :thumb:
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You know it! In the D70 under my DOdge cummins I run syn. because it sees high speeds and tows a lot. Obviously that would cause the most heat and wear, and that is where the synthetic should shine. In my K5 that just sees short high speed bursts and slow wheeling I use any 80-90 dyno oil :thumb:
 
Yeah, I get alot of highway miles...even when I do wheel...got to get there. I am thinking of useing the 75x90ns Redline, my parts place has it in stock...I figure I will just clean their stock out :D. Yeah I figured that is what I do with the fill hole...thanks for info!
 
For my trail truck with D60/FF14 combo with Detroits in both, I use Coastal 80W90 that I buy in a 5 gallon bucket. I change it out every six months or so in the front and yearly in the rear. More often of course if I run deep water or mud. Also, I prefer RTV to paper gaskets for differential covers. In my street driven truck, I used Mobil 1 75w90 with good results.
 
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