AKSoob Posted August 26, 2012 Share Posted August 26, 2012 I recently had a breakdown (timing belt issue) and I attempted to tow the car back home using a tow dolly (I know the error of my ways now) that I rented from uhaul. The tow dolly had the front two wheels up off the ground, and the rear wheels on the ground. I got about 100 feet down the road and my back tires locked up. Luckily I was taking it slow and was able to quickly stop leaving about 10 feet of tire marks from dragging. I waited about 2 minutes and drove about 20 more feet to get off the road, going really slow, with no lock-up problem. I have no idea what kind of damage I did, and am looking for advice on diagnosing anything or if anyone has had experience with something like this. I drive an 02 forester, 2.5L SOHC Manual Trans. Thanks. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted August 26, 2012 Share Posted August 26, 2012 check your manual = I believe on your MT you 'may' be able to tow all 4 down (perhaps with some distance/speed limitations and assuming tires are intact and all the same size) or on a flat bed. Quote Link to comment Share on other sites More sharing options...
AKSoob Posted August 26, 2012 Author Share Posted August 26, 2012 I ended up using a flat bed trailer, so all four wheels were off the ground. I just concerned that somehow I've done something bad to my car. I'm in the process of replacing several valves and so I can't drive it to see. Quote Link to comment Share on other sites More sharing options...
nickb21 Posted August 26, 2012 Share Posted August 26, 2012 (edited) Not to go too much off-topic, but for reference my 2002 OBW Manual states: Towing Vehicle with 4-wheels on the ground- Vehicles with Automatic Transmissions the traveling speed must be less than 20mph, and the distance less than 31 miles. [i think the general rule of thumb is don't do this regardless with an AT]. It does not give any speed or distance limits for a Manual Transmission (for 4 wheels down). Back on topic: I'm 1/2 surprised that the rear wheels actually locked up completely, I guess when the liquid in the viscous coupling gets hot enough it will basically seize. From reading the posts on this board there are two possible bad outcomes. 1) Liquid in the VC is "worn out" and will never really provide any "limited slip" between the front and rear. 2) Liquid in the VC is now a solid more or less, so when taking turns there won't be any give between the front and rear axles (eg. torque bind). I would argue there is still a good chance, that since you stopped almost immediately and let the VC cool down, you might have been able to save it, maybe just reducing the lifespan a bit. Is there a good way to diagnose while the motor is getting worked on other than to drive it? Edited August 26, 2012 by nickb21 . Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted August 26, 2012 Share Posted August 26, 2012 the viscous coupler that acts as the center diff sending power to the rear wheels ''grabs'' more when there is a speed difference between the front and rear wheels. since you stopped almost immediately you probably didn't do any real damage. if you had driven it home you would have killed it. but there is no way to tell until you drive it. if you feel binding in tight turns on dry pavement then you have damaged the viscous coupling. if it drives fine in tight turns you are ok. Quote Link to comment Share on other sites More sharing options...
1-3-2-4 Posted August 27, 2012 Share Posted August 27, 2012 Happened to me like 2 years ago.. my fuel pump froze up.. so the small city/town of Port Chester was was in only had ONE tow truck and all he had was the non flatbed.. So we was like lets try towing with two wheel up.. I told him it was not going to work.. And sure enough maybe 100-300 Ft you could hear the rear tires locked up.. So I had to wait another hour for him to get a flatbed.. in the dead of winter.. Why don't they just use a flatbed in the first place?? Anyways no damage was done and I drove it around when daylight came but being 24 F outside sucked with dress shoes on! Quote Link to comment Share on other sites More sharing options...
edrach Posted August 27, 2012 Share Posted August 27, 2012 Happened to me like 2 years ago.. my fuel pump froze up.. so the small city/town of Port Chester was was in only had ONE tow truck and all he had was the non flatbed.. So we was like lets try towing with two wheel up.. I told him it was not going to work.. And sure enough maybe 100-300 Ft you could hear the rear tires locked up.. So I had to wait another hour for him to get a flatbed.. in the dead of winter.. Why don't they just use a flatbed in the first place?? Anyways no damage was done and I drove it around when daylight came but being 24 F outside sucked with dress shoes on! Amazing how the tow drivers don't seem to understand the issue. I had a "difference of opinion" with a driver that showed up without the flatbed I had ordered. After he left I called another tow driver and he showed up with the proper equipment. First company tried to bill me for the tow; didn't happen after I spoke with a manager. Quote Link to comment Share on other sites More sharing options...
AKSoob Posted August 27, 2012 Author Share Posted August 27, 2012 I have the front of my car on jack stands while I'm working on the engine. The rear wheels are on the ground with the emergency break on. One thing that I've noticed that seems weird but may be normal is that when I put the car in gear, I can turn the crank shaft with no resistance. Front wheels spin freely. This makes me think that somehow the rear wheels are not connected properly. If I apply the brakes and lock up the front wheels with it in gear, I can't turn the crank at all. I don't think I should be able to turn the engine (crank) with the car in gear and the E-brake on. Any thoughts? Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted August 27, 2012 Share Posted August 27, 2012 turning the engine over by hand is so slow that there isn't really any speed difference front to rear. maybe if you did it for a long time the fluid would heat up and get ''grabbier''. so i would not worry about it. but I WOULD NOT try running the engine with the trans in gear, front wheels up and rear wheels down. unless you want to buy a new garage and spend some time in the emergency room. if you want to test it try lifting the rear wheels too. Quote Link to comment Share on other sites More sharing options...
AKSoob Posted August 27, 2012 Author Share Posted August 27, 2012 Hha. I imagine the front wheels would spin for about 10 seconds, and then I'd go through the back wall of my house. On the upside, I'd know that my AWD was still functioning properly. Quote Link to comment Share on other sites More sharing options...
1-3-2-4 Posted August 27, 2012 Share Posted August 27, 2012 I have the front of my car on jack stands while I'm working on the engine. The rear wheels are on the ground with the emergency break on. One thing that I've noticed that seems weird but may be normal is that when I put the car in gear, I can turn the crank shaft with no resistance. Front wheels spin freely. This makes me think that somehow the rear wheels are not connected properly. If I apply the brakes and lock up the front wheels with it in gear, I can't turn the crank at all. I don't think I should be able to turn the engine (crank) with the car in gear and the E-brake on. Any thoughts? Is this a auto or manual? I can pull my car forward I think I had it in 5th gear with the ebrake on when I had to take the crank pully off and the car started pulling forward a bit before the bolt finally broke free. Quote Link to comment Share on other sites More sharing options...
nipper Posted August 28, 2012 Share Posted August 28, 2012 Is this a auto or manual? . Thats what i was wondering, i couldn't tell be the posts. Quote Link to comment Share on other sites More sharing options...
AKSoob Posted August 28, 2012 Author Share Posted August 28, 2012 Its a 2002, 2.5L SOHC Manual Transmission. I'm just looking for a way to check to see if the AWD is still in tact besides driving it. I've got the engine pulled to replace the valves and head gaskets, and figured while I've got it like this, and am waiting for parts, I might be able to check the AWD somehow. Quote Link to comment Share on other sites More sharing options...
Subaru_dude Posted August 28, 2012 Share Posted August 28, 2012 Just throwing this out there although this is pretty much resolved... I believe you can remove the rear section of the driveshaft and tow it on a dolly. I've done that with a '95 Legacy 5spd. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 28, 2012 Share Posted August 28, 2012 The way the manual AWD trans works the fronts can spin independently of the rears, provided the speed difference is very little. With you cranking the engine by hand and the trans in 5th gear (as an example) your output ratio is going to be about 3.04:1 (assuming 3.90 FDR and .78 fifth gear). Which at the almighty hand-crank speed of lets say 15 rpm works out to... 0.1072935227269294 MPH. Roughly. If I did that right. :-p Point it, the difference in shaft speed from front to rear is not enough to create the fluid reaction needed to "lock" the center differential. The limited slip unit in the center diff is basically comprised of a series of plates with blades on the outer perimeter similar to a big windmill fan like this: The plates are put close to each other, and if they move the fluid around them (which is a heavy silicone based oil) moves with them. If they spin at different speeds the fluid is pushed by one set of plates, into the other set which creates resistance. The fluid reacts to heat and as it gets hot it actually thickens, which makes more resistance as the blades try to move through the fluid. If they move slowly, the fluid does not react, and doesn't push against the other sets of plates. So the wheels can spin and have the feeling of being separate from the rear wheels, even though they aren't. Howstuffworks.com has a page about Viscous couplings. http://auto.howstuffworks.com/differential5.htm Quote Link to comment Share on other sites More sharing options...
nipper Posted August 28, 2012 Share Posted August 28, 2012 http://www.autozine.org/technical_school/traction/tech_traction_4wd_2.htm (the viscous coupling) What fairtax4me is talking about with one correction. The fluid they use is silicon. the holes in the plates actually shear the silicon. When silicon heats up (from the shearing) it becomes thicker, which then creates the mechanical transfer of power to drive the wheels. Quote Link to comment Share on other sites More sharing options...
AKSoob Posted August 28, 2012 Author Share Posted August 28, 2012 Ok, thanks for the info Fairtax4me. That's a huge load off my mind. I thought I'd ruined the AWD. How fast would I have to turn it by hand in say first gear to see if it grabs the back wheels? Or is this a bad way to test AWD? Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 28, 2012 Share Posted August 28, 2012 That's pretty much how it works. One end spins faster than the other, makes heat, the other end gets more power as the fluid thickens. It's no so much about how many turns of the wheels it takes, but more how fast they spin. With 2 wheels off the ground (on the same side, drivers side for example) and the transmission in neutral the rear wheel (spun by hand) should turn the same direction as the front wheel at the same time and roughly the same speed or just slightly slower. With ONE wheel off the ground (doesn't matter which) the wheel should be able to spin but with a fair amount of resistance if you try to spin it fast. Quote Link to comment Share on other sites More sharing options...
torxxx Posted August 28, 2012 Share Posted August 28, 2012 you dont even have to remove the back half of the drive line. (not to mention a lot of the drivelines have the cv joint shaft in the middle not the flange to flange like the Loyales and what not) Take the 6 14mm bolts out of the rear diff bracket (ones that hide the driveline flange) pull the 4 12mm bolts that connect the driveline to the rear diff, seperate the flanges and then reinstall the cover. it will make some noises but it wont hurt anything. We've towed cars with a front wheel dolly from Canada to Alaska that way, nothing got hurt. And i wouldnt really worry about the center diff for now. Get your engine back in, and go drive the car. Thats the only REAL way to test it Quote Link to comment Share on other sites More sharing options...
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