I have a jeep TJ with a Detroit in the rear and a ARB up front. So what gear oil should i be using????? syntec75w 90 or regularly gear oil.......Nick

Synthetic would be the best, but standard gear oil would be fine too.

Synthetic would be the best, but standard gear oil would be fine too.

X2, both will work, it just depends on the money you want to spend.

Being that diff oil is the most neglected (typically) fluid in any vehicle, if you can afford the synthetic, go for it...

I would go with the synthetic b/c its only a few bucks more and it could help you in the long run...

Lockers do not require that special friction modifiers that limited slip diffs do. Plain old 80w-90 works best for all-around use. I run 85W-140 in mine since I don't care about viscosity resistance, won't ever run the truggy in really cold weather, and most certainly qualify under the "extreme" use category.

If your mudding or doing water crossings you might as well go with regular and change it more often.

For the detroit I have found that a 50-/50 mix of the Redline hi-shok and their 80/90 works really good.

Since the axles are the lowest lubricated point in the vehicle and therefore the first to get dunked in mud & water, I run conventional oil and change it frequently. Synthetic's biggest benefit over conventional is that it doesn't break down as rapidly as conventional, so for me it would be money wasted to use synthetics in the axles. But I do use synthetic in my engine, tranny, and t-cases.

As far as what weight oil to use, I have found that automatic lockers (Detroit, Lock-Right, etc.) are more "street-friendly" with a heavier-weight oil. The thicker oil quiets them down and somehow keeps them from "popping" and "squirming" as you drive down the road. I guess the thicker oil dampens their moving parts. Instead of 80w-90 oil I prefer 85w-140 and have had zero issues after 15 years of this.

For the detroit I have found that a 50-/50 mix of the Redline hi-shok and their 80/90 works really good.

I installed Redline Shock proof oil in my TJ. Why does mixing it help. I have noticed it has weird road characteristics sometime. So I wasn't sure if mixing it helped. I was changing my fluid tonight so I am glad that I found it.

X2

On the 85-140 Non-synthetic for the Detroit

Called Detroit today about my front Truetrac (shoulda gota Detroit) and they said to make sure to use Non-synthetic oil for both Detoit and Truetrac.

X2

On the 85-140 Non-synthetic for the Detroit

Called Detroit today about my front Truetrac (shoulda gota Detroit) and they said to make sure to use Non-synthetic oil for both Detoit and Truetrac.

did they give you a reason?