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Discussion Starter · #1 ·
Recently changed out my open diffs and 3.21's for a front selectable locker and the Yukon Dura Grip limited slip, along with 4.10 gears. I'll deal with the locker in a later report. Vehicle is a 2012 JK, 3.6, 6-speed manual, set up with 265/75/16 BFG All Terrain tires.

Up front let me state that I'm a long-time fan of limited slip differentials, on street or off-pavement rigs. I've had quite a number of them over the years, from nearly ineffective well-worn stock units to very aggressive aftermarket limited slip diffs. I know their handling quirks, and I like driving a limited slip equipped vehicle.

I liked the 3.21's, and the open diffs. The "BLD" function worked well for mild wheeling. It was actually very impressive, but I wanted stronger off-pavement capability.

Rockridge 4WD did the install, using synthetic gear lube and a limited slip additive.

The Yukon Dura Grip:






The gearing change was impressive. From a start there is no more slipping of the clutch to get going. Let the clutch out and the little JK leaps forward effortlessly. In town I find myself cruising around in 4th instead of 3rd. Out on the two-lane highway at 50 - 60 mph, I'm using 6th instead of 5th, and am turning 2300 rpm at 60 mph, roughly. The 3.6 is very comfortable at that rpm. Mixed in town and two-lane highway driving sees the Jeep averaging 16.5 mpg, up about 1.5 mpg from what I saw with the 3.21's.

I doubt I'll ever see those 22 - 23 mpg figures I used to see out on the open road, but for the mixed in town and up in the hills and out on the two-lane driving I generally do, the JK is actually getting somewhat better fuel economy.

Yukon's Dura Grip features four springs, pre-loading clutch packs. It's a very traditional limited slip design that appears to be very well built.

On pavement, in and out of town, it's barely perceptible. I know what a limited slip rear end feels like, and I did pick up on it right away. Occasionally pulling out into traffic there's a brief scuffing of the inside rear tire, just a chirp. On dirt, the rear of the Jeep stayed planted and I noticed no wheel spin, even going up a fairly steep, dry, slope with loose rocks and gravel over a hard surface. Normally I preferred going up that slope in four-low (with the stock 3.21's and open diffs) but now I go up it in two wheel drive, using first and second gears as necessary.



In 4-low, first gear, the JK idles along at a very slow pace now, slower than walking.

The gears and limited slip are new to my JK, and my initial impression of both the gears and the Yukon Dura Grip is very favorable!

Regards, Guy
 

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Thanks for this write up. I am considering changing from my 3.73 gearing to the 4.10. Am a little disappointed with the responsiveness from my current set-up.
 

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Great write up and pics. What size tires are you running? Mine's in the shop this week for a regear to 4.10s with trutracs front and rear.
 

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Discussion Starter · #4 ·
Thanks guys.

The 4.10's seem to be a real good match with the Pentastar & manual transmission. BTW, out on the highway my computer was reading 19.5 mpg yesterday, so maybe there's hope that the long-trip fuel economy won't be too bad...

I'm running 265/75 BFG A/T's on 16" rims. They're about 31" tall, about the actual size of most 32's. Might go to 285's (33's) late this summer or early in the fall.

If anyone gets the Dura Grip or a similar aggressive rear diff, be aware that it can induce some handling peculiarities, particularly on snow & ice.

Guy
 
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