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Discussion Starter #1
hey what do you guys think, is 80w90 to light for 7.17? i imagine that steep a gear must have tremendous stress. let me know what your running.
 

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I run 6.17s and have used valvoline 85w140 for a few years now... No problems and even bought the gears used
 

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The best thing to run with any offroad gear set is a synthetic 250w oil like Redline, Swepco, or Amsoil.
 

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E. Spengler
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Why run synthetic when it doesn't pull heat away from the gears? The diff feels cooler because of it not pulling heat away.
1) That don't make no sense. If the heat's building up in the gears, it's going somewhere eventually (unless you're only talking about a brief run).

2) Got a source? "Synthetic bad" sounds suspiciously like "Efi bad/carbs good!"
 

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Why run synthetic when it doesn't pull heat away from the gears? The diff feels cooler because of it not pulling heat away.
All I know is multi million dollar race teams run synthetic gear oils like Swepco 250, and I've had great luck with similar oils.
 

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Currie Ent. did a study years ago on this affect, read a little bit else where, and the folks that make hi9 and mega 9 have also said this.

Yes, it will probably pull some heat, but not what it should. The hi 9 folks said gears in the 200's degree and above is not good.

If your paid to run the Swepco products and then your gear sponsor is changing out the gears all of the time, the true effect may not show.
 

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plain old 80/90 is all you need.the oil doesn't keep them from breaking.
X2

If you were overheating the oil, or overworking the oil (think racing)

Then you will wear the gears out faster, which will cause breakage... from worn out gears.

Chances are if you are running 7.17s, then you ain't racing.
 

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Discussion Starter #12
thanks for the comments, i was just wondering about it because dana lists 7.17s as for "industrial use" so I was thinking is a d60 came in an industrial vehicle would the manual say 80/90?
 

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hey what do you guys think, is 80w90 to light for 7.17? i imagine that steep a gear must have tremendous stress. let me know what your running.
If your a crawler, it doesn't matter, anything is fine. If you are a racer, it matters a great deal.
 

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Conventional vs. synthetic argument aside, in a crawler application that rarely sees max speeds of ~50mph I've had much better luck running a straight 140w conventional oil than I did the conventional or synthetic 70-90 weight oils. My application isn't near controlled enough to say for sure that thicker oil was better (maybe I'm just getting better at setting up gears, or gears are getting better quality, or maybe I'm just getting smarter at driving) but I know the gears have been much happier with thicker oil. My pirate educated guess is that the thicker oil is providing more shock absorption to the gears themselves. On the flip side I'm sure it's harder on pinion bearings, but they're not what's failing me, so not too concerned with that.

With my heavyweight diff oil experience so far I wouldn't hesitate to go 250w amsoil in the diffs, but right now they leak constantly & I hate throwing $$ oil in there to watch it leak all over my shop floor. :homer:
 

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thanks for the comments, i was just wondering about it because dana lists 7.17s as for "industrial use" so I was thinking is a d60 came in an industrial vehicle would the manual say 80/90?
Problem is you're reading a manual for an Application that you don't have.

I've found that redline heavy shock proof seemed to help the super deep gears last.
 

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hi-steer ninja
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well, ford and dodge factory fill their 1 ton truck rear differentials with synthetic oil from the factory and warranty them for 100k miles pulling 14k#'s. considering they will change fasteners mid year production run to save 1c per bolt, I would say synthetic oil must have tested better.. the ford 75/140 synthetic seems to protect the sterling rear axle well, they seem to last over 250k miles without issue unless water gets into the diff..
 
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