Yesterday I changed the fluid in the diff. I used 75w90 synthetic. I always thought if it was synthetic it had the ls lube in it already. I believe the oil was from citco. I drove about 15 miles then stopped for an hour. When I backed out of the driveway I noticed the limited slip was grabbing. So today I dropped the oil and used mobil 75w140 with crc ls additive. Now the mobil oil says it has the ls additive in already but I wasn't taking any chances. Seems to be okay now. Some ford sites say to use 75w90 and some say to use the 75w140. Some say to use the additive and others say not too. I hope I did whats right.
95 f 250 12 bolt rear. I think its a dana 60.
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The rear axle in your Ford is a Sterling 10.25".
Ford used Dana 60's in F250's up until the mid 80's. Dana 60's have 10 bolts on the rear cover.
75W140 with LS add is fine.
Ford used Dana 60's in F250's up until the mid 80's. Dana 60's have 10 bolts on the rear cover.
75W140 with LS add is fine.
LS additive won't hurt anything, and the 75W140 won't either.
Different diff, but Ford's suggestion to quiet down 8.8s filled with 80W90 was to switch to 75W140.
Different diff, but Ford's suggestion to quiet down 8.8s filled with 80W90 was to switch to 75W140.
Yeah thanks people. Hope I didn't waste the 75w90 citco syn for no reason. Im wondering if I couldof just put the ls additive in that oil and ran with it. The axle has 42k on it now so its kinda new. How long is the mobil 75w140 syn gear lube good for.
After dumping the original fill, you can run syn for a long time in a diff. 100K miles + would be safe assuming the truck doesn't do a lot of towing, and assuming no deep water crossings (over the hub). If you can't stand to run it that long, drain it again after 50K miles. Anything less than that would be a waste of good fluid. Differentials don't get really hot relative to an engine or trans, and there isn't a lot of wear metal after initial break in. Odds are due to the age of the truck, you will need to replace an axle seal or pinion seal before the fluid actually needs to be replaced again.
Draining the factory fill early is always a good idea though since diffs have a fair amount of break in metal floating around. Usually the factory fill will be an opaque dark grey color from all the break in junk. Despite that, Ford's interval in the maintenance manual for my truck is 150K miles! I drained the factory fill at 50K. It was nasty. I then ran Valvoline DuraBlend syn blend for 30K, then drained that 30K later when I decided to go full syn. That was a waste since the DuraBlend looked practically like new. I have been running Royal Purple since and haven't changed it yet (70K miles).
Most people never change diff fluid, so you're already ahead. I suspect most differential failures are caused by fluid leaking out from a bad seal that goes unrepaired.
You probably could have just put the LS additive in the Citgo and run it for a normal interval with no issues, but honestly LS chatter would freak me out too, and I would have gone with new fluid too just because.
Draining the factory fill early is always a good idea though since diffs have a fair amount of break in metal floating around. Usually the factory fill will be an opaque dark grey color from all the break in junk. Despite that, Ford's interval in the maintenance manual for my truck is 150K miles! I drained the factory fill at 50K. It was nasty. I then ran Valvoline DuraBlend syn blend for 30K, then drained that 30K later when I decided to go full syn. That was a waste since the DuraBlend looked practically like new. I have been running Royal Purple since and haven't changed it yet (70K miles).
Most people never change diff fluid, so you're already ahead. I suspect most differential failures are caused by fluid leaking out from a bad seal that goes unrepaired.
You probably could have just put the LS additive in the Citgo and run it for a normal interval with no issues, but honestly LS chatter would freak me out too, and I would have gone with new fluid too just because.
You did fine. I'm currently running Delo ESI 85w140 with Redline LS additive in mine. You may consider adding the factory Ford finned cover P/N 8C3Z4033A (about 75 bucks depending on your source) from a later model truck to keep the fluid cooler and add some bling to the rear. https://cglapps.chevron.com/msdspds/PDSDetailPage.aspx?docDataId=76979&docFormat=PDF
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