80w90 or 75w90

[dommiel74]

Is there any benefit or harm in using a 75w90 gear oil (synthetic) when 80w90 conventional is specified?

 

[salesrep]

Not substantially.
Use it it if ya got it.

 

[ConfederateTyrant]

There is no issue, as both are a 90 weight gear oil, regardless of the Xw number. The synthetic will be a better choice than any dino gear oil.

 

[wileyE]

This comes up all the time at a bike forum for a shaft drive case. The spec is sae90w GL5, but try and find a straight 90?
Guys swear up and down that any other grade won't be as good, so they pay the price for OEM and specialty fluids.

 

[Pablo]

Actually the cold weather properties between the two vary substantially. Without typing out all the specs, a 80W dino gear oil pours at -16°F and a 75W syn pours at -67°F.

There would be no harm using a 75W when 80W is called for, as long as the fluid stays within the range specified for a 90 when 100°C.

http://www.lubrizol.com/products/automotive-gear-oil/J306.asp

 

[dommiel74]

Quote:

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Actually the cold weather properties between the two vary substantially. Without typing out all the specs, a 80W dino gear oil pours at -16°F and a 75W syn pours at -67°F.

There would be no harm using a 75W when 80W is called for, as long as the fluid stays within the range specified for a 90 when 100°C.

http://www.lubrizol.com/products/automotive-gear-oil/J306.asp

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Yes, I did look at that. There is a fairly large difference at 40c, but at 100c its very little.

DruaBlend:
Vis @ 100c(cSt) 14.8
Vis @ 40C (cSt) 136

Synpower:
Vis @ 100°C (cSt) 14.5
Vis @ 40°C (cSt) 100

P.S
Anyone know of a good siphon for getting the old gear oil out. There is no drain hole, and I cannot remover the cover.

 

[D Bone]

You wrote the following in the "30wt in high ambient temps" thread, maybe you should follow your own advice.

Quote:

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"Dude seriously, relax. Just use what the manufacturer requires and change it when needed".

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[salvageyardteen]

Quote:

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Anyone know of a good siphon for getting the old gear oil out. There is no drain hole, and I cannot remover the cover.

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NAPA sells one, pretty cheap too. Very slow doing it.

 

[rpn453]

For gear oils meeting the same performance specifications:

Benefits of 75W-90: remains liquid in extreme cold and increased fuel economy when operating below 100C (so almost always, unless you do a lot of towing).

Benefits of 80W-90: cheaper to produce.

 

[ARB1977]

Quote:

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Actually the cold weather properties between the two vary substantially. Without typing out all the specs, a 80W dino gear oil pours at -16°F and a 75W syn pours at -67°F.

There would be no harm using a 75W when 80W is called for, as long as the fluid stays within the range specified for a 90 when 100°C.

http://www.lubrizol.com/products/automotive-gear-oil/J306.asp

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Man thats a huge difference.

 

[dommiel74]

Whats that d bone? all I see is:
*** You are ignoring this user ***

Anyways, why would I go out and buy 3 quarts of 80-90 if I can use some of the 5 quarts of the 75-90 my neighbor gave me?

 

[dommiel74]

Quote:

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Quote:

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Anyone know of a good siphon for getting the old gear oil out. There is no drain hole, and I cannot remover the cover.

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NAPA sells one, pretty cheap too. Very slow doing it.

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Yes I have used one of those and it is SLOW!!
I found one at walmart, it was around 10 dollars, but it looks like it will get the job done in a few mins.

 

[mikeg5]

just make sure your diff oil is hot when you try to suck it out. it will come out a lot better.. drive it around for 15 mins or so and when you get back commense to getting the old diff oil out..btw your rear gear box can open. its just sealed shut. you can get the seal stuff at any autoparts place.