Topic: Auto Locker Affects Mileage?

[chrisfranklin]

I tend to doubt this, but have you heard anything about auto-type lockers (aussie, lockrite, detroit ez or carrier-included types) affecting gas mileage?  (I thought through the set up of the standard open differential front-end versus a front- end with an autolocker and didn't see any additional wear/friction which might cause lower mpg on the autolocked setup).  Am right/wrong 

[Jeffy]

You're probably losing a point or two (MPG) with the locker up front because of the extra energy it takes to move the pinion and front driveshaft.  If you had a TJ, you'd see it would probably be closer to 2 then 1.  With a YJ, you wouldn't get extra tire wear but with a TJ you would.  This is because the locker will cause a bit of understeer till it unlocked.  Those times when it stays locked and you don't turn as hard, the tires will scrub a bit more.  (Some people disconnect their front driveshaft from the yoke and tie it up.)  Still, a manual hub conversion would be a better solution and regain any lost mileage or wear.

When you put the locker in the back of either YJ, TJ, or whatever, you will see a bit more more tire wear.  Gas mileage might change a bit since you are basically 1WD on occasion.  Axle wrap in 1WD is common.  Anything that causes the tires to chirp will cause wear.  Then shifting, and the locker goes from 1WD to 2WD, it will shimmy and that probably causes more wear since it's an abrupt shift.  Although, most people will learn how to drive to minimize this so any change in wear or mileage will probably be minimal.

[chrisfranklin]

That probably explains why I currently run about 16mpg in the city versus 18 mpg prior to going to with slightly larger tires and the front locker.  I guess going with a rear auto locker too would probably dog the mileage even further.

[Bounty Hunter]

The amount a locker could affect your mileage, especially in the front of a YJ, is going to be too insignificant to notice.  You took a hit on mileage due to the tire change.

[chrisfranklin]

So, we got Jeffy saying mileage gets dinged a little with the auto-locker and Bounty Hunter saying not really.

Next tire change, I was going to go with at least 31" BFG MTs (or maybe try the Firestone Destination tire) and do some one inch shackles and trimming to get them to fit. But, at current 16mpg on 29s, my mileage is going to take a bit hit doing this.  Probably only recourse is $1000 for new gears to maybe keep load on the engine close to original (yeah right) and maintain 16mpg city!

I may stay on 29s forever  Have still done some ok So Cal. trails on these go-kart tires - Miller Jeep, Rowher Trail etc. Wouldn't be pretty, but you can do the Rubicon on 29s apparently.

[Jeffy]

So, we got Jeffy saying mileage gets dinged a little with the auto-locker and Bounty Hunter saying not really.

Next tire change, I was going to go with at least 31" BFG MTs (or maybe try the Firestone Destination tire) and do some one inch shackles and trimming to get them to fit. But, at current 16mpg on 29s, my mileage is going to take a bit hit doing this.  Probably only recourse is $1000 for new gears to maybe keep load on the engine close to original (yeah right) and maintain 16mpg city!

I may stay on 29s forever  Have still done some ok So Cal. trails on these go-kart tires - Miller Jeep, Rowher Trail etc. Wouldn't be pretty, but you can do the Rubicon on 29s apparently.

What I'm saying is , it's such a small amount that you may or may not notice any difference depending on your driving.  1-2 points with any fluctuation from day to day driving won't really be measurable.  If you take your mileage over a long period of time you may see a difference if everything else stays the same. (which it probably won't.)  Now if you haven't recalibrate your speedometer from your tire change, then that could easily account for the difference.  Tire pressure will also come into play.  Less pressure and you'll increase the rolling resistance.  Theoretically, it all could add up. I'm sure I'm putting more wear on my tires and I'll probably lose a bit of mileage but if you're really worried about 1-2 points, then you might want to consider another form of transportation for daily usage.

[chrisfranklin]

If we're talking "2 points" as in 2mpg, thats 40 miles of city driving on the 20 gallon tank.  For me that means two or three more days I don't need to go to a fueling station. Who likes accelerating one's need to visit Exxon?   

If I don't use it as a daily I'll probably go with a diesel, regardless of fuel prices.

[Jeffy]

If we're talking "2 points" as in 2mpg, thats 40 miles of city driving on the 20 gallon tank.  For me that means two or three more days I don't need to go to a fueling station. Who likes accelerating one's need to visit Exxon?   

If I don't use it as a daily I'll probably go with a diesel, regardless of fuel prices.

Yes, but are you sure those two points are attributed to one thing (the locker)?  With your speedometer off, that will easily throw off your mileage to look worse then it actually is.  Spirited driving, or even lugging the engine will cause it to use more fuel.  Drive at highway speeds often and it will drop.  So unless you can really rule out everything else, there is no real definite answer.

[chrisfranklin]

Yes, but are you sure those two points are attributed to one thing (the locker)?  With your speedometer off, that will easily throw off your mileage to look worse then it actually is.  Spirited driving, or even lugging the engine will cause it to use more fuel.  Drive at highway speeds often and it will drop.  So unless you can really rule out everything else, there is no real definite answer.

Good point. 

Funny thing is my speedometer with the 235s seems to sync almost perfectly with my GPS mph readings - 65 on the speedo is 65 on the GPS. If anything, on the original 205s, my range-per-tank and corresponding mileage was reading high - 65 on the speedo would read about 61 or 62 on the GPS.  Perhaps I have been at 16mpg since day one and my supposed mileage decline (locker, tires) was really based on an initial calculation derived from a base-line range that was inflated by the smaller tires ("inflated by the smaller tires" - no pun intended  ).  I guess its a little late to try to be truly scientific in determining the cause of any supposed mileage decline I may have experienced.   

[riverman]

I am running an Aussie Lock up front on a TJ and a YJ so I can tell you that you are going to loose about 2 MPG at least but it also adds a lot of wear and tear to the drivetrain. We haven't gone to the lock out hubs yet but I think that is the only way not to wear out the drivetrain and get back the gas mileage.

[chrisfranklin]

I am running an Aussie Lock up front on a TJ and a YJ so I can tell you that you are going to loose about 2 MPG at least but it also adds a lot of wear and tear to the drivetrain. We haven't gone to the lock out hubs yet but I think that is the only way not to wear out the drivetrain and get back the gas mileage.

Heck, so I add a rear aussie, I am looking at a 4mpg drop, presumably, right?  The hidden costs of auto-locker traction.

[Bounty Hunter]

Heck, so I add a rear aussie, I am looking at a 4mpg drop, presumably, right?  The hidden costs of auto-locker traction.

I highly doubt it, the majority of driving is straight-line and the locker has no effect on straight-line driving.  You'll notice little to no drop in mileage.  I think it has a larger affect when used in the front, spinning half of the drivetrain that ordinarily doesn't spin in 2wd.

[Oilsmoke]

I agree with bounty hunter statement.
 Last Tank I avg 16.8    on 30x9.5x15 MT and that going to work that only 2.5 miles from home and the jeep is never warmed up and out of the closed loop.

For me the question is do I build a DD or a Jeep. I still have a hard time with this question.