4wd-2wd questions

[dennyt]

Howdy,

I'm the proud owner of a '94 Loyale wagon with 211k on the clock. My mods are more in the direction of fuel economy than performance, so next spring (after ski season!) I'm thinking of removing the driveshaft, rear diff, and rear halfshafts.

 

Some obvious questions:

-Will the transfer case leak if I pull the driveshaft?

-Will I need the outer CV stubs to hold the rear wheels together? I'm guessing yes, so I'll probably grab some from a junkyard so I can take them apart & run just the outer stubs.

 

I've had fun reading some of the posts here, thanks for being a great resource.

 

[skishop69]

Is it Ft pr PT 4wd? If it's part time (and it should be) you will see no gains in fuel economy and would be wasting your time pulling everything. Should you want to continue, yes, the rear output shaft will leak. You can't just stuff a plug in it as there is nothing to keep it from popping out. Yes, you will have to install rear stubs to keep the bearing preload. IE, stop them from flying off the car while you drive. Either way, if it were FT, you might see maybe 2mpg. Still not worth the effort in my opinion.....

[dennyt]

Thanks for the info. Yes, this is part-time 4wd, with a manual transmission.

 

I still think I would see an improvement from pulling these parts. Stirring up that diff oil, accelerating / decelerating the rotational parts, and dragging the whole thing around (50-100 lbs?) adds up.

 

I started at 24mpg, getting 36 now, and going for 40. Several 2% improvements can add up. Just as much fun has been learning & finding a reason to play around with a "non-performance" car.

[Subruise]

your biggest gain would be to remove the hatch and replace with clear plastic, those things weigh alot. ive also heard you get better mileage with an ej swap, yes even with higher displacement. a motor that works less burns less

 

 

RV

[notliving]

What are some of the things you've done to achieve 36mpg? I'm getting about 25mpg right now and would love to be in the 30's.

[dennyt]

What I've done so far:

• Higher tire pressure (44-50psi)
  
• Installed a kill switch on the injector ground wire, so I can coast with the engine off (down hills, to stop lights, etc) without turning off the headlights. The brake booster works for 3 pushes of the pedal, after that I bump-start the engine to refill it. On long down-grades I leave it in gear.
  
• Removed the clutching fan, kept the electric fan
  
• Covered up the lower grill opening with coroplast for the winter
  
• Upgraded to a heated O2 sensor
  
• Put a potentiometer in parallel with the coolant temp sensor to trick the engine into thinking it's warmer, which reduces cold startup enrichment
  
• Removed the power steering pump, drained & capped the lines (it's not that difficult to park it). Put a shorter belt on, removed the AC belt.
  
• Removed the AC fuse so I can run the windshield defogger without turning on the AC. I put it back in during the summer.
  
• Removed passenger side mirror. Tests show these are ~1% each. Installed a wide-angle rearview mirror, but if the car is full of gear, I really miss the right sideview. Looking into lower-profile mirrors.
  
• Swapped out the hubcaps for some 4-slots from '86, and filled the slots in with coroplast.
  
• Moved the front turn signals flush with the bumper (better visibility at intersections, too - they used to be buried)
  
• Synthetic oil in the engine, tranny, and rear diff
  
• Installed a vacuum gauge to monitor engine load, and to avoid "flooring it". Keep the needle above 2 to avoid open-loop enrichment.
  

 

My next big project will be a front bellypan, similar to this: http://autospeed.com/cms/A_2456/article.html

 

There's a general list of mods here:

Ecomodder.com

 

The biggest change you can make is in your driving style. Avoid idling, combine trips to keep the car warm, etc.

Driving Techniques

Edited November 29, 2010 by dennyt

[Subruise]

wow.....thats a lot of homework done, bravo. maybe a coroplast hatch then.....

[MilesFox]

Even in FWDmode, the rear axles and diff and driveshaftare still rotating anytime the car is moving.

 

If you remove the rear axles, the driveshaft anddiff will remain stationary.

 

You can remove the entire rear axles, since the bearings are contained on its own stub. There are roll pins to remove on the outer ends of the rear axles, same as the insides.

 

you can remove the rear half of the driveshaft with the diff, and leave the front half of the driveshaft mounted with the carrier bearing and into the trans. The driveshaft will be stationary sonce its not being driven in FWD, and there is no rear axles or diff to turn it.

 

the spfi injector shuts down when you are off the gas, and only comes back on once the car is at idle(during decel)

[WoodsWagon]

Biggest gain would be to remove the rear axles off of the hub stub shaft. You only have to pull one axle out to see good gains. Most trucks with ADD (automatic differential disconnect) only unhook one axle from the diff. The spider gears in the diff and the remaining axle will still rotate but that's way less power consumption than spinning the ring and pinion and the propeller shaft.

 

Pull one or both rear axles and you will see a decent gain in MPG. The weight loss of dumping the rear drivetrain is negligible compared to the convenience of just tossing a pair of axles in when you want to go camping for a weekend.

[GeneralDisorder]

If you really want improvment from going to 2WD then you need to install a 2WD transmission - the final drive ratio/tire size is much more favorable for mileage.

 

Losing the 4WD stuff is troublesome and only a half-measure that won't gain you nearly as much as changing to a more favorably geared transmission.

 

Take it a step farther and do all these mods to a 2WD 5 speed, non-turbo XT.

 

GD

[dennyt]

Thanks for all the tips. Yeah, a 2WD coupe would be better, I remember getting 30mpg without even trying when I had one of those. But I want to keep the wagon, it's what I've got, it's running well, and I use all of the space at least once a month. 3-4 people with backpacking / climbing / skiing / biking gear will fill the wagon right up.

 

How much higher is the 2WD final drive ratio?

[GeneralDisorder]

Hhhmmm - the chart I have doesn't show any differences in ratio between the two - but the tire size is definitely different. The 2WD's used 175/70R13's while the 4WD's used 185/70R13's - 2WD DL's ran 165 or 155 IIRC. Even smaller yet.

 

Tires have to match transmission or your speedo will be off - which will throw off all your economy calculations as well.

 

Installing a 2WD tranny is a much cleaner option than removing the 4WD components alone. It wil further reduce weight as well.

 

GD

[Scott in Bellingham]

I have a stock EA82 2WD tranny I would trade for all the 4WD stuff you remove , Im 1-1/2hrs away

[dennyt]

Thanks all, but I'm not ditching the 4wd parts. This would be a spring/summer/fall swap-out. I love the 4wd in the winter!

 

I'm liking the idea of just removing the rear axles, that sounds like it will accomplish most of what I want.

 

I checked my odometer on the highway, it reads +0.3 miles over 10 miles on my summer tires (165/80-13) and my snow tires alike (185/70-13), that's 3% high, so I'm getting closer to 35mpg.

[jdemaris]

-Will the transfer case leak if I pull the driveshaft?

 

 

I had a couple of late 80s Loyale wagons. One just front wheel drive (useless!), and the other 4WD. Both with 5 speed manual. There was no noticeable difference in fuel mileage, but 3/4 of my driving is on hills, dirt roads, and not highway cruising. I also don't know what the axle-ratio was for the front-wheel drive. My 4WD had 3.90 to 1 ratio. All my 4WD wagons have 3.90s (I've got over a dozen). Final-drive ratio can make a huge difference.

 

Now, Loyales with three-speed automatics were absolutely terrible on fuel mileage and also had an awful 4WD setup - but that's a different story.

 

I suspect that you're going to see very little gain by removing all those parts. Maybe 2 MPG in ideal conditions? For the back of your trans - you need to fasten a drive-shaft stub in there to keep the oil in.

 

As to unhooking rear half-shafts - if you're going to do it, remove both. I would not trust the differential side-gears to withand constant turning if you unhooked only one. Some rears are designed for that, but I doubt this one is. Many differentials have no bearings involved when those side-gears are turning, since they not meant to turn all the time.

 

On somewhat related conversion. I have a 1999 Dodge AWD Grand Caravan . So does a friend of mine. Same year, same axle ratios, same engine, same trans. He recently removed the entire rear drive. Both rear stub-shafts, rear driveshaft, etc. He gained absolutely nothing in regard to highway fuel mileage. In fact, mine does almost 2 MPG better, but I assume that's because of my tires . . . and the engine is maybe in better shape. I just drove 2200 miles at averaged 23 MPG going 75 MPH most of the time. His van with the rear guts removed is getting a best of 21 MPG.