annoyingrob

I'm just curious if this is normal. When I'm driving with the front unlocked, around town, I usually average 17-18mpg with the auto. When I lock the front hubs, even keeping it in 2HI, my mileage drops quite significantly to around 13mpg. That seems like a lot of drag to me. Doesn't it? Front diff fluid was changed last year, and level was still good a few months ago. All grease points were greased last a season ago too. CV boots are in great shape, with no abnormal noises.

briholt

did you get a resolution to this?

abecedarian

with the hubs unlocked, the front diff can spin around just fine, wasting energy without ever transmitting it out to the CV shafts. Lock the hubs and the CV shafts are forced to turn regardless of the 4WD lever.

RobD

I noticed minimal difference, if any (430-450 kms per tank unlocked, 425-440 kms locked).

I notice a bigger difference leaving the engine idling to warm up and when they switch to winter fuel (375-390 kms) per tank.

874runnersr5

ditto

rattlewagon

agreed with the winter driving. its been 0 here for the past couple of weeks, ive been getting around 16 mpg compared to my normal 20.

i havent had this runner (22re) long enough to notice any hub difference, but with my truck (3vze) there was a huge difference when the hubs were locked, deff notice it going up hills.

RICE ETR

We recently got some snow here...~12"...so I have been keeping it in 4wd.....definitely a huge reduction in mpg. Also I agree with the winter blend...it has more ethanol in it around here which you need more of (volume wise) to make the same power....so you get worse mileage.

wyoming9

iTrader: (1)

i would think the fact of winter gas blend the lower temps longer idle times and the hubs locked in all mixed into the equation give you the loss of mileage.

Check next summer i bet the loss with the hubs locked is not as great.

Any time you put added loads on the system the gas mileage will drop.

Flash319

If your truck is none ADD (tag says 86 so not ADD) then you will see a huge difference. I have in the past with different vehicles. You might as well be in 4x4 if you have the hubs locked because you are turning almost everything you would be in 4x4. I bet you get 13mpg in 4x4.

RobD you must be ADD. With that I have noticed very little to no difference because you are only spinning the CV's.

RustBucket

iTrader: (1)

Agreed, I have non-ADD and notice significantly more drag when the hubs are locked. Feels like I lose 15 horsepower. I also have a true-trac up front but it shouldn't make a difference when cruising.

annoyingrob

It may be related to the winter gas, I never thought of that. Anyways, I haven't found a resolution to this yet, as my truck spun a bearing, and is out of comission until I can find a new motor.

RobD

It was ADD, now it has Warn hubs. All my ADD stuff has been removed and my slider on my front axle is connected full-time.

93YotaMonster

my truck gets terrible gas millage with the hubs locked, my fix is leave them un locked. it sucks to leave them unlocked cause wen you need four wheel drive you have to get out and lock them, but sometimes you don't have that option

Flash319

[QUOTE=RobD;51316589]It was ADD, now it has Warn hubs. All my ADD stuff has been removed and my slider on my front axle is connected full-time.[/QUOT


Off topic but why did you do that? Was it not working right or something? I love the ADD with manual hubs added. In the winter I leave the hubs locked and in the summer I can unlock the whole front end.

RustBucket

iTrader: (1)

Probably to simplify things... there's also some debate as to non-ADD half-shafts being stronger.

Flash319

By half shafts do you mean CV shafts? If so, I use them interchangeably and was unaware of any difference. They are the same part number.
If you are talking about the long side shaft out of the diff, then maybe but I would think the CV's would be the weak link.

aviator

the winter gas is the biggest issue... my mileage went from around 570km a tank to 500km give or take... my old 87 with Aisins took a small hit when I kept the hubs locked in winter maybe 2-3kms difference...
Got everything to switch my ADD to Aisins (a couple yrs. ago lol) just have'nt got of my duff to do her... have to fix a new power steering issue first then I'll throw them on... hopefully I'll get back a few kms of range.

RustBucket

iTrader: (1)

Flash, I mean the solid half-shafts. But you're right, either way they wouldn't be the weak link. Who's heard of people breaking those?

RobD

After I did my 3.4 swap, I couldn't be bothered tracing all the wiring and vacuum lines necessary to keep the ADD working properly. I had a store credit at Lordco Autoparts and decided to go with the Warns, since they were pretty cheap. Personally, I would have gone with Aisins, but I'd have better luck finding Jimmy Hoffa versus a good used set of Aisins around here.

91 4Runner

Too bad you weren't closer, I could shoot you a set.... They show up all the time in one yard here....