This is topic How do you change your gear oil? in forum Tech Talk at Northern California Ford Owners  .


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Posted by 50sneak (Member # 8533) on :
 
How do you change your gear oil? for your gears in your rear end on a 91 5.0 mustang GT???
 
Posted by Blind (Member # 3052) on :
 
pull the diff cover, drain
replace diff cover with silicone for a gasket all around, torque the bolts
pop the fill plug on the other side of the diff, fill with ~2 - 2.5 qts of synth gear oil and a bottle of friction modifier from ford for the trak-lok.
 
Posted by Peter Hatch (Member # 7676) on :
 
What ratio of friction modifier to gear oil do you guys use? I just filled up my diff after pulling the axle but I'm curious.
 
Posted by 50sneak (Member # 8533) on :
 
To tell u the truth I don't even know I'm was goin to ask yal but I'm just about to royal purple all my oils engin tranny gear oil and coolent
 
Posted by asskickn88 (Member # 4957) on :
 
I think the synthetic oils don't need the friction modifier but I could be wrong. Maybe there is synthetic with it already in it that I was thinking of. If you just pulled an axle and lost a small bit of fluid then I'd just top it off with gear oil but if you drain the whole thing then you need to add a full bottle or tube of the friction modifier.
 
Posted by 92stangLX (Member # 3252) on :
 
quote:
Originally posted by Peter Hatch:
What ratio of friction modifier to gear oil do you guys use? I just filled up my diff after pulling the axle but I'm curious.
You can get a small bottle from the Ford dealer. Just add the whole thing and then put in the gear oil.
 
Posted by 89foxstang (Member # 5908) on :
 
yeah i just mix the modifier with the gear oil in the bottle before its empty so i know it mixes well. It probably would anyway but im just ocd like that haha
 
Posted by Blind (Member # 3052) on :
 
quote:
Originally posted by asskickn88:
I think the synthetic oils don't need the friction modifier but I could be wrong. Maybe there is synthetic with it already in it that I was thinking of. If you just pulled an axle and lost a small bit of fluid then I'd just top it off with gear oil but if you drain the whole thing then you need to add a full bottle or tube of the friction modifier.
some do, but not all, and it doesn't hurt to add the friction modifier, I asked several people at the ford dealer about it
 
Posted by v-town50 (Member # 4920) on :
 
see ive heard that your not supposed to use synthetic with the trak lok because the clutches have a harder time grabbin and lockin up
 
Posted by 1HaTCheD5LiTEr (Member # 8269) on :
 
im sure that the synthetic wont hurt in the least bit as long bit as long as you use the LSD additive which you should use every time anyways [burnout]
 
Posted by Blind (Member # 3052) on :
 
quote:
Originally posted by v-town50:
see ive heard that your not supposed to use synthetic with the trak lok because the clutches have a harder time grabbin and lockin up
all svt vehicles come with synth diff gear oil from the factory.
 
Posted by Jawsgear (Member # 8080) on :
 
Most positraction manufactures now days are not going to warranty any differential that has had synthetic oil in the differential. It is damaging the clutches and not allowing them to function properly. We run a standard 80w90 Valvoline with a ford friction modifier. Rule of thumb is 4oz of additive to every 2 quarts of oil. We use synthetic only in high heat situations like drag racing or road racing to keep the gears cooler.

Jeff
 
Posted by 85gtcarbro8du-up (Member # 5169) on :
 
a little tidbit of 411. you probly wanna pop the diff plug before you do anything else, that way you know your gonna be able to fill it after you drain it. i used to work at a qwik lube and you wouldnt believe the amount of dumbass people who had their cars towed in because they drained the oil before popping the fill cap. or even had some kind of stripped or rounded out type of plug for oil pan, trans, or rear end.
 
Posted by Jawsgear (Member # 8080) on :
 
That is actually a great suggestion. I can't even count the times people have brought us their car for a diff oil change and had the fill plug stripped. Excellent suggestion and is actually the first step our mechanics do before opening up any differential.
 




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