Converting Loyale to 2WD

[Tom63050]

Thinking of taking a long road trip in my Loyale. To save gas, I want to convert it temporarily to 2WD. I think I can do this by simply detaching the rear axles. As I understand it, when the car is in 2WD, the rear wheels drive the axles, which drives the rear diff, which drives the driveshaft going to the transmission. Lotsa unnecessary friction, using up gas. With the rear axles off, as long as I don't put the trans in 4WD, the driveshaft won't spin, right?

 

For that matter, I might as well leave it as 2WD except for in the winter. Feedback please.

[subarunuts]

Sure - you can remove them. Won't save you a single gallon of gas tho. The savings the 2WD's see is from their gearing - mostly the 3.7 final gear ratio - and to a lesser extent weight reduction from not having all that stuff. Also the 2WD's used 175 tires instead of 185 series. All that combined got them about 7 to 8 more MPG or so.

 

Just removing the gear friction from the diff will get you less than nothing. Seriously. Plus if you really need 4WD, you won't have it.

 

By all means test the theory tho - remove them both and drive it through a tank of gas before you go. Only takes 20 minutes to pull both of them assuming they aren't rusted to the stubs (common).

 

Besides... if it really were that simple don't you suppose that some engineer would have thought of this years ago and put locking hubs on the rear wheels?.... if it meant being able to advertise 5 more MPG you bet your arse it would have been done.

[Tom63050]

Sure - you can remove them. Won't save you a single gallon of gas tho. The savings the 2WD's see is from their gearing - mostly the 3.7 final gear ratio - and to a lesser extent weight reduction from not having all that stuff. Also the 2WD's used 175 tires instead of 185 series. All that combined got them about 7 to 8 more MPG or so.

 

Just removing the gear friction from the diff will get you less than nothing. Seriously. Plus if you really need 4WD, you won't have it.

 

By all means test the theory tho - remove them both and drive it through a tank of gas before you go. Only takes 20 minutes to pull both of them assuming they aren't rusted to the stubs (common).

 

Besides... if it really were that simple don't you suppose that some engineer would have thought of this years ago and put locking hubs on the rear wheels?.... if it meant being able to advertise 5 more MPG you bet your arse it would have been done.

 

Interesting reply, thanks, but not what I expected. Really, this won't save gas? I believe the 3.7 and the 175 tires would about cancel each other out. The shorter 175 tires will spin a llittle faster than 185s, and the 3.7 will spin a little slower than the 3.9. The weight of a rear end, axles and a driveshaft is less than an adult, so that alone shouldn't account for any significant gas savings on the 2WDs.

 

Any other replies?

 

As far as not putting on locking hubs, I think that's more likely a cost-cutting measure, since these cars were never intended to be driven off-road by the factory.

[subarunuts]

As far as not putting on locking hubs, I think that's more likely a cost-cutting measure, since these cars were never intended to be driven off-road by the factory.

 

So is that why Subaru didn't sell brush guards, winches, roll bars, and factory lift kits?? Oh wait - they did.

 

It's not just the 3.7 - it's the gearing of the 2WD 5 speed trans too.

 

I'm not just spouting hot air - I own an 84 wagon that I converted from 2WD to 4WD, and I know the numbers from before and after. I loved getting 35 MPG with the Weber when it was 2WD. Same engine, same carb - with 4WD gearing and larger 29" tires I get 20 - 22 MPG.

 

Larger tires do indeed decrease your RPM - but they also are heavier, and their larger mass requires more power to reach and maintain the same speed as smaller tires. At any rate, it's a bell-curve of sorts. One cannot say that no matter what, larger tires will ALWAYS result in better mileage. It's useful when considering problems such as this to look at the boundary cases - on one extreme you have tires of 0 size, or 1" even if you like. Obviously it can be easily understood that this would be a bad idea. Take the other extreme - tires of say 50" in diameter.... The engine would never be able to drive them, so.... it's a balancing act, and the idea is to run the engine at it's optimum RPM to get the best mileage. The 2WD gearing is very effective in this respect.

 

There are yet even more issues to contemplate too - the flywheel is heavier, and the clutch is smaller on 2WD's - that changes the target RPM. The distributor curve is different for some models..... etc, etc.

[Tom63050]

So is that why Subaru didn't sell brush guards, winches, roll bars, and factory lift kits?? Oh wait - they did.

 

It's not just the 3.7 - it's the gearing of the 2WD 5 speed trans too.

 

I'm not just spouting hot air - I own an 84 wagon that I converted from 2WD to 4WD, and I know the numbers from before and after. I loved getting 35 MPG with the Weber when it was 2WD. Same engine, same carb - with 4WD gearing and larger 29" tires I get 20 - 22 MPG.

 

Larger tires do indeed decrease your RPM - but they also are heavier, and their larger mass requires more power to reach and maintain the same speed as smaller tires. At any rate, it's a bell-curve of sorts. One cannot say that no matter what, larger tires will ALWAYS result in better mileage. It's useful when considering problems such as this to look at the boundary cases - on one extreme you have tires of 0 size, or 1" even if you like. Obviously it can be easily understood that this would be a bad idea. Take the other extreme - tires of say 50" in diameter.... The engine would never be able to drive them, so.... it's a balancing act, and the idea is to run the engine at it's optimum RPM to get the best mileage. The 2WD gearing is very effective in this respect.

 

There are yet even more issues to contemplate too - the flywheel is heavier, and the clutch is smaller on 2WD's - that changes the target RPM. The distributor curve is different for some models..... etc, etc.

 

You may be right about what you wrote above. When spring comes, I will unhook the rear axles and see what happens, and let the Board know the results. BTW, when I put the PK lift on the Loyale and put on the heavier 14" steel rims with 27" tires, my highway mileage stayed the same at 28. The slower revs canceled out the greater weight the axles were pushing.

[joenik]

u wont save any gas. i ran an 92 loyale wagon with the rear drive shaft removed for about 6 months and it made no difference.

[subarunuts]

All things being equal, a mild tire size change technically shouldn't have a lot of effect on hiway mileage. The massive decrease in *overall* mileage that I experienced I think is because I'm running heavier chevy rims, 29" tires, and an '82 D/R trans that has lower gearing than any other year of the D/R. It makes 4th gear somewhat usable, but the higher revs aren't nice to the mileage....

 

Around town mileage has almost got to decrease tho due to the increase in weight, and inertia. Getting those big tires moving takes a lot of power, and running through the gears is painful on the RPMS. In order to achieve useful acceleration I have to rev it higher before switching gears knowing that my next gear will bog unless I get it up there. Could just be the way I drive it, but I like to be able to get out of my own way at least.

 

You have the advantage of SPFI too - that's nice. Although I do get about 25-28 with a Weber on my stock Brat, so not a lot different I guess. Still nice to run at any angle.

 

Weber on my 2WD wagon - 32-35 MPG

Weber on my 4WD Brat - 25-28 MPG

Weber on Lifted 4WD Wagon - 20-22 MPG

[Tom63050]

u wont save any gas. i ran an 92 loyale wagon with the rear drive shaft removed for about 6 months and it made no difference.

 

OK, but the main source of friction probably isn't the driveshaft itself, it's the right-angle turn the rotation makes when it goes through the diff. I'll give it a good fair test--150 highway miles with and 150 highway miles without the rear axles on, and report the results.

[subarunuts]

No doubt about that - there is definately friction there..... I'm just saying that it's in the same ball park as the FDA attempting to elliminate over-the-counter inhalers because they destroy the ozone (no joke). My point being that any benifit comming from the practice will almost certainly be outweighed by a very large cost in the end. IE - stuck in the mud/snow/ice/poop with no 4WD, and no way to install the axles.

 

I think the 1 or maybe 2 MPG that you get from checking your tire pressure regularly would be more worthwhile.

 

I think under properly controlled laboratory conditions the difference could probably be measured.... but in the field there are conditions beyond control - temperature being a big one - another being the seasonal formulations of fuel that change my mileage all the time without me doing anything.... To remove the inherent flaws in the test, at the very least you need a control set - something driven exactly the same way, at the same times, and the same distances. Preferably several of each - two test vehicles, and two control vehicles. Then you might get usable data - only after the variables were canceled out by properly filtering it tho.

[Tom63050]

No doubt about that - there is definately friction there..... I'm just saying that it's in the same ball park as the FDA attempting to elliminate over-the-counter inhalers because they destroy the ozone (no joke). My point being that any benifit comming from the practice will almost certainly be outweighed by a very large cost in the end. IE - stuck in the mud/snow/ice/poop with no 4WD, and no way to install the axles.

 

I think the 1 or maybe 2 MPG that you get from checking your tire pressure regularly would be more worthwhile.

 

I think under properly controlled laboratory conditions the difference could probably be measured.... but in the field there are conditions beyond control - temperature being a big one - another being the seasonal formulations of fuel that change my mileage all the time without me doing anything.... To remove the inherent flaws in the test, at the very least you need a control set - something driven exactly the same way, at the same times, and the same distances. Preferably several of each - two test vehicles, and two control vehicles. Then you might get usable data - only after the variables were canceled out by properly filtering it tho.

 

For sure about checking tire pressure. I'll take the axles off in spring and fill the car with non-winter gas. Both runs will be with the same type of gas, on two days that are as identical as possible regarding wind and temp. And of course I'll put the axles back on in the fall. I haven't used this car off-road, so no getting stuck in the mud.

[NoahDL88]

So is that why Subaru didn't sell brush guards, winches, roll bars, and factory lift kits?? Oh wait - they did.

 

Not on the same model though, and you can hardly call the outback struts a "lift"

 

Page 1 of the owners manual "your new Subaru is designed as an "all road" car and extreme caution should be used........"

 

Not to say they can't be offroaded either.

 

 

As far as MPG, slow down 5 mph, you'll notice a great deal of increase in your MPG.

[Tom63050]

Not on the same model though, and you can hardly call the outback struts a "lift"

 

Page 1 of the owners manual "your new Subaru is designed as an "all road" car and extreme caution should be used........"

 

Not to say they can't be offroaded either.

 

 

As far as MPG, slow down 5 mph, you'll notice a great deal of increase in your MPG.

 

Don't know of any of these mods for a Loyale, except maybe front mudflaps. Sounds like Brat mods more than anything.

 

Of course slowing down helps--gas mileage decreases exponentially, when air friction gets greater as speed increases. But I want to run a controlled (as much as possible) real-world test on the same car, with and without rear axles. If I find out there's no/very little improvement, that's fine too. It's not good science to want a certain result so much that you lose objectivity.

[subarunuts]

Not on the same model though, and you can hardly call the outback struts a "lift"

MPG.

 

SOA did offer some factory (well - probably "Dealer" install, but you get the idea) lft kits back in the Gen 1 Brat days.... Was only like 1", but still - the intention is obvious.

 

Brat owners manuals say that if you intend to go "off road" with people in the jump seats you really ought to get the optional roll bar... really - the EA81 owners guides say that.

 

Don't know of any of these mods for a Loyale, except maybe front mudflaps. Sounds like Brat mods more than anything.

 

The design and layout of the subaru platform has changed very little - especially between a Brat and a loyale. They are nearly the same in too many ways to list. At least in every way that counts, I'm sure most would agree their capability is quite similar.

 

It's true that most of those things have not been offered for the Loyale series... but that's largely due to marketing, and liability concerns. You don't actually find many truck makers offering extreme off-road equipment either (relative to the capability of the vehicle - winches and roll-bars are pretty extreme for an otherwise stock Brat. You never saw TRD offering stuff like that for their 4WD Tercel now did you? Let alone snow plows). They leave it to the aftermarket, and focus on just building the vehicles.