1500 front differential - synthetic vs conventional fluid

SLT617 · Jun 14, 2017

I have a 2011 ram 1500 and need to service the front differential. The manual says to use conventional fluid on the front and synthetic in the rear for 1500's and synthetic for front and rear for 2500-3500's. Went to the auto parts store and they only had synthetic so I just grabbed it anyway.

Should I be okay using synthetic fluid in the front differential for a 1500? I typically follow the manual but I know people who switch to synthetics in newer vehicles and not have any problems.

I just wanted to confirm that others have done this in the 1500's to make sure it's safe.

VB712 · Jun 14, 2017

Changed front and rear on mine with full synthetic

powderbrad · Jun 15, 2017

They probably figure the front only gets a fraction of the use the rear does. So factory fill will be mineral to save pennies.

I don't see harm in you adding synthetic.

SLT617 · Jun 19, 2017

well it's too late to turn back now - I just used the synthetic fluid. It took a lot longer than expected because the front diff is harder to get through but my old fluid was like black honey and luckily had no metal shavings. I've driven it for just a few days and I've gotten about a 1 mpg increase already. I'll drive it around another week or so to see if the mpg stays at that level though.

Frisk · Jun 19, 2017

I always use full synthetic.....The extra cost pays for it self in increased protection and way better fuel mileage in the cold winter months.

powderbrad · Jun 20, 2017

Diffs get pretty warm when used and thin out like any oil. You can tell a MPG difference??

SLT617 · Jun 20, 2017

powderbrad said:
Diffs get pretty warm when used and thin out like any oil. You can tell a MPG difference??

Yeah. I spend most of my time on the highway but have a farm so my truck has been getting 16-17mpg. I've been averaging about 17-18.5 this week since changing it but we'll see where I stand after a few tanks of gas. I've read that changing out old diff fluid adds about .5-1 mpg so it's in that range.

On the highway it gets about 20-21mpg but the stop and go in the city and driving it on the farm that kills the mpg real quick.

Frisk · Jun 21, 2017

I used to have an old Toyota 4x4. When it was -30 I had to let the clutch out slowly in neutral to let that tranny spin up to warm up the tranny fluid. After letting it idle for about 5 min I could then back out of my driveway but I had to slip the clutch to get truck rolling as the front and rear diffs were full of molasses. After a few miles of driving the fluid had thinned out to the point that you could start from a stop normally. The same effects are present on the Ram but the use of an automatic transmission and way more engine power mask the problem. With the old Toyota 4X4 I did a full fluid change so that everything was synthetic......An unbelievable difference in the cold weather driving.

smiley · Jun 21, 2017

I notice the most difference using synthetic when 40 or colder and when I first start out. To me it is worth it just for its ability to not thicken as much when cold vs conventional. I always use synthetic in differentials and I actually run 75W-140 front and rear.

1500 front differential - synthetic vs conventional fluid

SLT617

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VB712

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powderbrad

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SLT617

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Frisk

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powderbrad

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smiley

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