Disable AWD?

[TIMINTEXAS]

Got a 99 legacy SUS and want to know if disabling AWD to save gas is OK to do long-term. (don't need it in Texas too much)

[Manarius]

Got a 99 legacy SUS and want to know if disabling AWD to save gas is OK to do long-term. (don't need it in Texas too much)

It doesn't save gas. The weight is there regardless of the AWD being disabled and that's the mpg killer.

 

This has been covered many many times.

[nipper]

It doesn't save gas. The weight is there regardless of the AWD being disabled and that's the mpg killer.

 

This has been covered many many times.

 

Many many many many times. You want better gas mileage, get a honda.

 

(odd how we always suggest a honda).

 

nipper

[SUBARU3]

or a 2WD Subaru. The last of the 2WDs were 1996 and I have noticed they are getting harder and harder to fine and the price is going up on them too.

 

Impreza 93-96

Legacy thru 1996

 

I return mid 30s-high 30s on a 95 Impreza FWD 1.8 "L"

 

Todd

[audio_file]

(odd how we always suggest a honda).

nipper

 

just sounds better than, "find a used Neon" (36mpg in it's last config) or "go pay way too much for a TDI VW" (40+ mpg's, but overpriced and unreliable)

 

my answer, find an old import from the main four . . . honda, toyota, subaru, nissan/datsun . . . it amazes me that with 25-30 years of "development" cars today have worse fuel economy than their predecessors (almost all models from any of the above were rated at 30+mpg's in the 70's!)

 

that conversation though =

 

chris

[idosubaru]

yep it won't make a difference. i've done it on manual and automatics before and zero difference. not worth the trouble. but the answer to your question is "no" it won't hurt anything in my opinion. but i would also say you're better off keeping the car running as it was designed verses like that.

 

have it converted to FWD 5 speed if you want better gas mileage.

[Bucky92]

Alot is how you drive it also...I have gotten 34 mpg out of my 08 Impreza 5 door 5 spd..took nursing to do it...but now I am a regular steady 30-31mpg.

[1997reduxe]

Yeah but that FWD fuse feature is sure something.

Speaking from personal experience this week, I

have been driving my 97 Legacy AWD for a while with

varying levels/types of noise coming from directly

under the car. I believe (hope) it's a u-joint, and

on thursday it was getting much worse. (It seems

like it happens mostly under early acceleration).

but anywho, i put the FWD fuse in to check if it would

change anything, and the noise pretty much disappeared.

Wow, they made these cars with forward-thinking.

[CNY_Dave]

Just to examine this issue to the fullest degree possible- how much weight would be shed, and how much would mileage go up, if you pulled the rear driveshaft, the pumpkin, and the rear half-shafts?

 

You could just use the shells from a pair of outers to keep the wheel bearings together.

 

Would you get 1? 2? 3 more mpg?

 

All that stuff weigh 50 lbs?

 

 

Dave

[Gloyale]

Would you get 1? 2? 3 more mpg?

 

All that stuff weigh 50 lbs?

 

 

Dave

 

 

hmmm.... rear section of driveshaft, 2 half shafts, rear diff......more like 200 Lbs.

 

If you were to use a 2wd trans you could shed even another 50-100 lbs.

 

I know my 2wd (carbeurated) 85 GL gets 33+. My 4wd 86 GL (carbed) got 25 with a light foot.

 

So 8 mpg improvement???

[johnceggleston]

Just to examine this issue to the fullest degree possible- how much weight would be shed, and how much would mileage go up, if you pulled the rear driveshaft, the pumpkin, and the rear half-shafts?

 

You could just use the shells from a pair of outers to keep the wheel bearings together.

 

Would you get 1? 2? 3 more mpg?

 

All that stuff weigh 50 lbs?

 

 

Dave

the problem is not converting you AWD to FWD and increasing you mileage, it's that you can't convert it back with out a LOT of work. so once you do it it's not like you can change it back for the wekend. also, i suggest you put in the FWD fuse under the hood, if it's an auto, and try driving it in FWD. if you've had your subaru for any lenght of time, you won't like it. there is a very noticable difference in how it handles.

 

so as stated above, get a honda, or a 96 FWD subaru.

 

the parts interchange software that all the junk yards use actually lists a FWD auto trans for 97, but i've never heard of anyone actually having one. i wonder if the option will come back wit hgas prices going up.?

 

the weight you save by removing all that hardware is like not having an extra passenger. there will be some savings in gas, but i suspect the real savings come from not wasting engine power pushing all the mechanics, not the 200lbs or so.

 

the other way to acomplish this would be to install thoses axle disconnects that they sell for cars w/ auto trans towed behind an RV. then you could put in the FWD fuse, disconnect the rear axles, and as long as the duty c holds out you are FWD, w/o the weight savings. now calculate the cost of mods vs. the gas savings .....

[frag]

Maybe bearing and gear friction could also be taken into account ?

Less weight, but also less friction.

[nipper]

hmmm.... rear section of driveshaft, 2 half shafts, rear diff......more like 200 Lbs.

 

If you were to use a 2wd trans you could shed even another 50-100 lbs.

 

I know my 2wd (carbeurated) 85 GL gets 33+. My 4wd 86 GL (carbed) got 25 with a light foot.

 

So 8 mpg improvement???

 

Not to mention that is force directly applied to 50-100 lbs worth of mass, plus the viscocity of the rear diff lube.

 

Its not the same as having a 200 lb passenger in the car. My guess would be 3-4 mpg improvement, but like i said get a honda. If your not using the RWD part, then there is no reason for all the extra supporting structure in the body either.

 

nipper

[idosubaru]

Just to examine this issue to the fullest degree possible- how much weight would be shed, and how much would mileage go up, if you pulled the rear driveshaft, the pumpkin, and the rear half-shafts?

 

You could just use the shells from a pair of outers to keep the wheel bearings together.

 

Would you get 1? 2? 3 more mpg?

 

All that stuff weigh 50 lbs?

 

i've done all of this and more. i'd guess it's around 150 pounds reduction.

 

i haven't seen much difference between having all the rear drive train in place verses removing it for highway driving. i don't track city driving enough to comment on that, but i would guess it's more noticeable there.

 

weight doesn't make much...actually any noticeable...difference for highway driving. i can carry lots of weight or passengers and get the same highway mileage either way. so weight isn't much of an issue for those incurring high mileage and fuel costs. i'm sure large loads would make a difference but a passenger or two worth of weight doesn't make any noticeable difference in my experience for highway mileage.

 

the cheapest car is the one you own so if it's a financial decision then do a cost benefit analysis and make your next purchase reflect nippers sentiments.

[CNY_Dave]

I'm just looking at it for the fun of looking at it.

 

Disable my AWD and I won't be able to confound the sporty cars by stomping on it on the on/off ramps.

 

 

Dave

[hankosolder2]

Interesting. I just looked at fueleconomy.gov and compared the EPA figures for a '95 Legacy (FWD, 5MT) 21 City / 29 HWY and '95 Legacy (AWD, 5MT) 19 City/ 26 HWY.

 

The large spread in highway driving can't be accounted for by weight (I agree with grossgary on this point) so it must be due to something else- either additional drivetrain friction or gear ratios (or a flaw in the EPA's procedure!)

 

Any thoughts?

 

Nathan

[johnceggleston]

Interesting. I just looked at fueleconomy.gov and compared the EPA figures for a '95 Legacy (FWD, 5MT) 21 City / 29 HWY and '95 Legacy (AWD, 5MT) 19 City/ 26 HWY.

 

The large spread in highway driving can't be accounted for by weight (I agree with grossgary on this point) so it must be due to something else- either additional drivetrain friction or gear ratios (or a flaw in the EPA's procedure!)

 

Any thoughts?

 

Nathan

 

is my memory right, does the 95 FWD have a 3.7 final drive ratio?? higher, more economical than the AWD.

[CNY_Dave]

Interesting. I just looked at fueleconomy.gov and compared the EPA figures for a '95 Legacy (FWD, 5MT) 21 City / 29 HWY and '95 Legacy (AWD, 5MT) 19 City/ 26 HWY.

 

The large spread in highway driving can't be accounted for by weight (I agree with grossgary on this point) so it must be due to something else- either additional drivetrain friction or gear ratios (or a flaw in the EPA's procedure!)

 

Any thoughts?

 

Nathan

 

 

Well, it takes *some* extra fuel to accellerate the extra mass, but yeah, that's a "one time" thing on the highway. More loss if its hilly.

 

Don't under-estimate the powerloss in the rear shaft U-joints, rear pumpkin, and rear CV joints. And if its slipping, the powerloss in the front/rear clutch.

 

Dave

[Gloyale]

is my memory right, does the 95 FWD have a 3.7 final drive ratio?? higher, more economical than the AWD.

 

Final Ratio differences FTW.

[1997reduxe]

Well, it just so happens I have been considering this very much in the past few days.

I put the FWD fuse in due to serious rumblings and noise in my drive train, and I swear the car runs like it did when I first bought it (at 140K).

SMOOTH!!!

and it seems it puts much less strain on the engine, etc.

(Of course, this is probably subjective since it has 100K+ wear since I bought it.)

BUT. does anyone have a link to the actual process or parts to remove (aside from the above) where someone actually did this? and any success?

Thanks for any info.

Actually, it's just wonderful to see my baby run nicely again, without the necessary need to fix the train, as I already need to get a front axle replaced, inner tie rods, and I've had replacement used struts for the past year that I could finally consider having put on, given that I could dispense with the rear concerns.

Also living in Texas.

[CNY_Dave]

Well, it just so happens I have been considering this very much in the past few days.

I put the FWD fuse in due to serious rumblings and noise in my drive train, and I swear the car runs like it did when I first bought it (at 140K).

SMOOTH!!!

and it seems it puts much less strain on the engine, etc.

(Of course, this is probably subjective since it has 100K+ wear since I bought it.)

BUT. does anyone have a link to the actual process or parts to remove (aside from the above) where someone actually did this? and any success?

Thanks for any info.

Actually, it's just wonderful to see my baby run nicely again, without the necessary need to fix the train, as I already need to get a front axle replaced, inner tie rods, and I've had replacement used struts for the past year that I could finally consider having put on, given that I could dispense with the rear concerns.

Also living in Texas.

 

 

Well, if the rear driveshaft bolts in at both ends that's pretty easy and straightforwards. Take it out, and pull the FWD fuse.

 

Then you could go nuts and pull the pumpkin and the half-shafts at your leisure. Just remember (I think) you need to put in a half-shaft outer stub end to hold the wheel bearing together.

 

 

Dave

[Hocrest]

Unless you want to modify your transmission, you'll need to leave in the front half of the driveshaft, the section from the trans to the carrier bearing. There are 4 bolts at each end of the back half of the drive shaft. Remove the rear diff and axles and replace them with stub axles from a FWD Leg or Imp (less rotating weight than an empty CV cup)

 

Weight savings;

Diff - 60lbs

Axles - 24lbs

1/2 driveshaft- 12lbs

stub axles - add 3lbs

TOTAL - 93lbs

 

If you take apart the trans and convert it to FWD;

Previous - 93lbs

1/2 driveshaft - 16lbs

Transfer drum/tailshaft - 8lbs

TOTAL - 117lbs

[johnceggleston]

Well, if the rear driveshaft bolts in at both ends that's pretty easy and straightforwards. Take it out, and pull the FWD fuse.

 

Then you could go nuts and pull the pumpkin and the half-shafts at your leisure. Just remember (I think) you need to put in a half-shaft outer stub end to hold the wheel bearing together.

 

 

Dave

 

yes, you will need the splined shaft, wheel end, of the axle mounted in the wheel hub to keep the bearing from decentigrating. you wil also need to keep the first section of drive shaft attached to the rear of the trans, or modify the trans so it will not leak fluid. every thing inbetween can go.

[montana105]

I'm going with Nipper on this,why destruct a fully functional car when you could part with it modestly and use that money on a Honda or something more efficient.

[CNY_Dave]

I'm going with Nipper on this,why destruct a fully functional car when you could part with it modestly and use that money on a Honda or something more efficient.

 

Its, like, bench racing, man. Like, y'know?

 

Besides, you never know when info like this will come in handy.

 

Dave