Keith Browning Posted April 29, 2008 Share Posted April 29, 2008 A few years ago I heard about removing the front driveshaft on an AWD Explorer to improve gas mileage. I know that all AWD vehicles take a hit in fuel economy so this sounds plausible. I don't think that this would cause any harm to the transfer case but I really have no experience with them other than I own one... can anyone think of a reason I shouldn't try removing my front driveshaft until the winter? Quote Link to comment Share on other sites More sharing options...
OHNO60 Posted April 29, 2008 Share Posted April 29, 2008 KEITH FORGIVE ME FOR SOUNDING LIKE AN IDIOT BUT TRIED THAT FOR CUSTOMER WITH A CHEVY AWD VAN .ACTUALLY WOULD ROLL IN PARK. NOT SURE EXACTLY HOW BUT MIGHT BE SAME RESULT WITH THE FORD EXPLORER. MAYBE LIKE 4X4 TRANSFER CASE BEING PULLED INTO NEUTRAL. /forums/images/%%GRAEMLIN_URL%%/shrug.gif. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted April 29, 2008 Author Share Posted April 29, 2008 The rear axle is always engaged in this AWD transfer case. The front axle is connected via a chain drive and the shaft is engaged automatically... well, here is the description from the manual: The constantly activated, automatic, all-wheel drive transfer case has no external controls. A two-piece aluminum case houses the assembly. The unit is chain driven. A non-repairable viscous coupling provides torque distribution to the front and rear transfer case outputs. The viscous coupling contains slotted alternating plates through which a high viscosity fluid flows. The resistance of the fluid shear causes the plates to transmit torque at the approximate ratio of 35 percent to the front output and 65 percent to the rear output. I don't see how disconnecting this would cause any damage but I just want to know is if anyone has done this and if they had any problems. There is a planetary gear set that acts like a differential between the axles and it couples the input shaft with the output shaft... looks like it is locked together, but I cant tell by the picture. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted April 30, 2008 Share Posted April 30, 2008 Keith, I think you would destroy the viscous coupling. It's a older explorer with a 5.0L? Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted April 30, 2008 Author Share Posted April 30, 2008 Its a 2001 5.0L. Do you think the viscus coupling would have problems being unloaded? Maybe. But it would just be going for a free ride, kinda like a torque converter with the trans in neutral. I better read the entire section in the manual. Quote Link to comment Share on other sites More sharing options...
Jeff_E Posted April 30, 2008 Share Posted April 30, 2008 This might be totally out in left field (I usually am). But I'm wondering - If the viscous coupling always diverts about 35% of the engines torque to the front T-Case flange, and you remove the shaft that transmits that torque to it's respective wheels, Aren't you then left with only 65% of the torque being utilized to actually propelling the vehicle. And if so, wont that 35% efficiency loss end up being worse for fuel economy than what the extra drag of the front driveline causes in the first place????? Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted April 30, 2008 Share Posted April 30, 2008 The planetary gearset is for HI and LO range.... It isn't used to couple front and rear... From memory - the rear output shaft is connected mechanically all of the time. When the speed of the front driveshaft differs from the speed of the rear, the viscous coupling will start to "drive" the front wheels through the chain and the lower sprocket. Removing the front driveshaft will have the front output simply "along for the ride" but the added stability offered by full time all wheel drive will be lost. Since you will still be changing the speed of a considerable amount of iron (axles, CV joints, cage, gearset), I'm unsure of what kind of mileage gains will be found. Not to sound like a dork, but the system has been positively identified as the AWD system and not the more common (from my experience, anyway) A4WD system? Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted April 30, 2008 Author Share Posted April 30, 2008 The planetary gear set is for HI and LO range.... It isn't used to couple front and rear... From memory - the rear output shaft is connected mechanically all of the time. Since this is AWD it does not have "Hi" and "Low" and there is no shifting or controls because it's All Wheel Drive - not 4X4. That would be A4WD. Since I never had one of these apart I did read the manual including disassembly and assembly. It is the second part which I left out that explains the power flow but I must be too tired to "get it" right now. OPERATION Torque flows through the input shaft to the front planetary gear assembly outward to the ring gear to the upper output shaft. Torque also flows through the front planetary gear assembly to the overdrive sun gear outward to the upper drive sprocket. The torque flow continues from the upper drive sprocket through the drive chain to the lower drive sprocket to the front output shaft. The viscous coupling provides the connection between the ring gear and the overdrive sun gear. This is one of those things I need to see with my hands. Time for bed! /forums/images/%%GRAEMLIN_URL%%/sleep.gif Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted April 30, 2008 Share Posted April 30, 2008 EWWWWWWW... and here I thought I'd seen them all... Actually opening the book, looks like the planetary carrier is the driven member with the ring gear driving the rear shaft and the sun gear driving the from shaft... It also appears that the viscous coupling is splined to the input shaft... making it the reactive member - the one that "holds" the sun gear (remembering that one part of the gear set needs to be driven and one member needs to be held to get anything done)... The viscous coupling resists any speed difference between the ring gear and the sun gear... Without a drive shaft to the front, the viscous coupling is going to be working it's heart out all the time. Maybe I'll stick to more conventional 4WD systems /forums/images/%%GRAEMLIN_URL%%/grin.gif Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted April 30, 2008 Share Posted April 30, 2008 ... Without a drive shaft to the front, the viscous coupling is going to be working it's heart out all the time. That is correct, Jim. Don't do it, Keith, or you'll burn up your viscous coupling. Also, if you need tires, replace all 4 as just changing the two worst worn ones is going to do the same thing to the viscous coupling. It will overheat and burn out. Keep your tires rotated regularily to even out wear. Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted April 30, 2008 Share Posted April 30, 2008 Also, even with just the front driveshaft out, what are you really accomplishing anyhow, as the front axle/differential is still turning, and this is where most of the resistance in the front end comes from, not the transfer case or driveshaft. /forums/images/%%GRAEMLIN_URL%%/2cents.gif Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted April 30, 2008 Share Posted April 30, 2008 Hey Keith pull the whole front dif, doors, deck lid, hood, any seats not being used, spare tire that should help get this beast a little lighter anyways. The little woman wouldn't mind driving it like that right? /forums/images/%%GRAEMLIN_URL%%/grin.gif /forums/images/%%GRAEMLIN_URL%%/poke.gif /forums/images/%%GRAEMLIN_URL%%/cover.gif Quote Link to comment Share on other sites More sharing options...
Mekanik Posted May 1, 2008 Share Posted May 1, 2008 Yeah you don't really want to mess with these A4WD systems. I had one of these years ago that had 2 tires replaces with a different size. The complaint was that the front diff would start on fire. The funny thing is that another shop replaced the front diff, only for the new one to start on fire too. The coupler was trying to keep both driveshafts turning at the same speed. Keith, I really think you would destroy the coupler in the transfer case if you did this. /forums/images/%%GRAEMLIN_URL%%/2cents.gif Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted May 1, 2008 Share Posted May 1, 2008 S'funny this thread should come up.... I finally got the parts to finish what is hopefully the last thing on a long list for an 03 Expedition... Customer drove back from some Gawd awful place in 4HI... on bare roads.... We overhauled the front diff (burned up - even melted the rubber mount bushings)... next the transfer case was replaced (burned up) and now I am re-installing the 9.75 diff... (also burned up)... And all of this leaves me feeling "burned up"... Quote Link to comment Share on other sites More sharing options...
eastendpowerstroke Posted May 1, 2008 Share Posted May 1, 2008 KEITH FORGIVE ME FOR SOUNDING LIKE AN IDIOT BUT TRIED THAT FOR CUSTOMER WITH A CHEVY AWD VAN .ACTUALLY WOULD ROLL IN PARK. NOT SURE EXACTLY HOW BUT MIGHT BE SAME RESULT WITH THE FORD EXPLORER. MAYBE LIKE 4X4 TRANSFER CASE BEING PULLED INTO NEUTRAL. /forums/images/%%GRAEMLIN_URL%%/shrug.gif.YES it will roll in park.. it's funny the guys in the stalls on both sides of me have awd explorers that within a week blew apart the CV end of the front shaft,the immediate solution was to yank the shaft and order parts, one woke to find his had rolled and was bumper to bumper with the school bus his wife drives and the other was roused from his slumber by the police knocking at the door asking why his explorer was parked in the middle of the road. /forums/images/%%GRAEMLIN_URL%%/surprise.gif /forums/images/%%GRAEMLIN_URL%%/rofl.gif Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted May 1, 2008 Author Share Posted May 1, 2008 I know about the tires, we have had more than one customer with tire related bucking and jerking caused by mis-matched tires. I guess I will leave well enough alone as far as my AWD is concerned. Thanks for helping me figure this out guys! Quote Link to comment Share on other sites More sharing options...
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