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what happens if you tow an AWD improperly?


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21 replies to this topic

#1 grossgary

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Posted 29 January 2005 - 10:04 PM

i've towed 3 subaru's, i know to disconnect the driveshaft and you should use a flat bed...blah blah blah, i'm not asking any of that.

what would actually happen if an AWD manual or automatic were towed with the back wheels on the ground and the front wheels secured? will something definitely break? maybe break? should break? sometimes? all the time? immediately? new transmission will be needed right away, eventually?
anyone ever actually ruined a transmission by doing this? i haven't actually ever heard from someone who had to replace a transmission because of this.

#2 mudduck

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Posted 29 January 2005 - 10:06 PM

I'm not sure if I would want to find out using my car. :lol:

#3 stngllhm

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Posted 29 January 2005 - 10:14 PM

i can't say for sure. but i would think it would just work the spider gears in the center diff hard.
at the same timeyou know it ca't be good for it even if it doesn't screw it up the first time. it will shorten its life span

#4 grossgary

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Posted 29 January 2005 - 10:25 PM

with all the emphasis on towing an AWD properly, i'm surprised at the lack of anyone who's actually had a problem with this.

#5 freedster

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Posted 30 January 2005 - 12:22 AM

I seem to remember reading that you could tow a 4WD suby Manual Tansmission by just putting it neutral if you kept all 4 wheels on the ground. Does that fly?

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#6 85Sub4WD

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Posted 30 January 2005 - 12:27 AM

I have a friend who owned a transmission shop and he has made a lot of money by fixing automatics that were towed with their wheels on the ground, so I KNOW you cannot tow an automatic (even in neutral) if the wheels are on the ground. If you have the AWD you cannot tow with the wheels on the ground either because it will overload the center diff (even a MT in neutral), and you will not have much left (plus there can be stability issues).
You CAN tow a 4WD MT car with its wheels on the ground because you can completely disconnect the driveaxels by putting it in 2WD mode and by putting it in neutral, so yes you can do that, but ONLY with that type of drivetrain. (On certain late 80's automatics yoy can insert a fuse so that you can tow it with the rear wheels on the ground, but there are specific instructions for those cars.)
In general, eventhough I have a 4WD MT car, I still put it on a flatbed tow truck if it has to be towed anywhere.

#7 felipe01forester

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Posted 30 January 2005 - 12:37 AM

If the car has a manual t-case, you can put the t-case in neutral, then put the gearbox in neutral, totally disconnecting the engine from the complete drivetrain. That's the only way you can tow a 4WD vehicle. But, since AWD is completely automatic and requires no operator intervention, there's really no way to completely disconnect the drivetrain from the transmission, I wouldn't try it. Subaru does make pretty heavy emphasis on this point in the owner's manual. Either way, most tow trucks sent out are flatbets, so that shouldn't be a problem.

#8 freedster

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Posted 30 January 2005 - 12:53 AM

Well, as light as my GL is, I could probably tow it myself somewhere behind my S-10 with on of those little RV yokes if I needed to take a second car with me sometime. Sounds like I can put it in 2wd and neutral and I'd be good to go. Thanks for the info.

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#9 calebz

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Posted 30 January 2005 - 01:19 AM

5 speed manual:

All four down ok
flatbed ok
towdolly with rears on the ground ok when driveshaft removed

Auto :
Flatbed ok
towdolly with driveshaft removed ok


Any deviation from the above will result in destroyed center diff

#10 RavenTBK

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Posted 30 January 2005 - 10:32 AM

<-- is the towman. I've asked similar questions in the past, and I dont blame the board for telling me "No, just dont do it" in every case. I ended up hitting several dealerships and speaking with the lead mechanics for real information on this subject.

All in all, its not good regardless, but in my case, it had to be done now and then, so I had to know what are the real limits.

For the latter AWD designs (OB, WRX, IMP):
Manual - 2 up 2 dn = destruction of the center lsd if pulled any more than 1/2 mi or so.. or over 15mph. tranny can be in any gear and/or neutral.

Auto - 2 up 2dn = destruction of the center diff if pulled any more than 4 miles, or at over 35mph. inserting FWD fuse extends the range to 6mi but speed requirements are the same.

Either way, dont do 2up if you dont have to. When I finally had to tow that bastard in the blue WRX for parking on the grass again, it helped to know a soft "limit" to where I wouldnt screw anything up.

If you pull it 2up, you'll definately feel the drag of the center section on your towing vehicle. You can ignore it, but dont ignore it if you know what I mean.

#11 subyrally

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Posted 30 January 2005 - 10:43 AM

other than granading the center diff, if you put an awd car on a tow dolly or on the hook, so to speak, you also will have th car jump out of the dolly that the front wheels are in. i think that its best to just not risk it and spring for a flatbed.

#12 calebz

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Posted 30 January 2005 - 11:22 AM

other than granading the center diff, if you put an awd car on a tow dolly or on the hook, so to speak, you also will have th car jump out of the dolly that the front wheels are in.


That won't happen if you secure the wheels properly.

If you don't secure the wheels properly, any car can hop off the wheel lift.


One other option I haven't seen covered here. Rear wheel dollies. Car goes on wheel lift like normal, but there are individual little rollers that go under the rear wheels. They have been very useful to me in the past for reposessions.

#13 subyrally

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Posted 30 January 2005 - 11:44 AM

there was a thread on nasioc where a guy in detroit , i think, that had his car towed to an impoundfor speeding. the cop called for a truck to take the car. they sent out a normal truck. within a few hundred yards of where they hooked the car, securing it proprly, it jumped the dolly and went into a jerseywall and destroyed the front end of the car.



That won't happen if you secure the wheels properly.

If you don't secure the wheels properly, any car can hop off the wheel lift.


One other option I haven't seen covered here. Rear wheel dollies. Car goes on wheel lift like normal, but there are individual little rollers that go under the rear wheels. They have been very useful to me in the past for reposessions.



#14 RavenTBK

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Posted 30 January 2005 - 11:46 AM

there was a thread on nasioc where a guy in detroit , i think, that had his car towed to an impoundfor speeding. the cop called for a truck to take the car. they sent out a normal truck. within a few hundred yards of where they hooked the car, securing it proprly, it jumped the dolly and went into a jerseywall and destroyed the front end of the car.

then it wasnt tied down correctly. its that simple.

#15 bushbasher

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Posted 30 January 2005 - 11:57 AM

another thing to consider is heat buildup. When you are spinning the rear output on the transmission, especially on an automatic, you wont be getting any oil to that area to cool it down. So at high speed or long distances you could be dealing with annealed bearings/output shafts, or even having it seize up on you.

#16 85Sub4WD

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Posted 30 January 2005 - 08:02 PM

bushbasher hit it on the nose -
MT are OK, as there is no oil pump in them (the oil is picked up by the moving gear teeth, however, AT has a pump driven by the engine, and if the engine is off, then it is not circulating oil. It's as simple as that. And transmission seizure is not unheard of.
There IS a MUCH better chance of a MT Soob with a center differential jumping off a wheel lift b/c the spinning rear/front wheels will transmit power through the CD to the wheels on the wheel lift, so you will either rip the CD, jump off the lift, or break the lift. One of the three is inevitable with CD cars, period. If you go SLOWLY (under 25mph) you MAY be fine, but it is still best to put it on a lift, and simply not risk it.

#17 WJM

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Posted 30 January 2005 - 08:09 PM

i've towed 3 subaru's, i know to disconnect the driveshaft and you should use a flat bed...blah blah blah, i'm not asking any of that.

what would actually happen if an AWD manual or automatic were towed with the back wheels on the ground and the front wheels secured? will something definitely break? maybe break? should break? sometimes? all the time? immediately? new transmission will be needed right away, eventually?
anyone ever actually ruined a transmission by doing this? i haven't actually ever heard from someone who had to replace a transmission because of this.


Did you buy crazyhorse's XT6?

One thing thats interesting is...the center diffs on the FT4WD EA82/ER27's are OPEN. There is no LSD or clutchplates (auto) to screw up.

However, there is the severe speed difference from one side of the diff spinning...and one side NOT.

So on a regular diff, open....if you sat there in...say a ford mustang, and did a one wheel burnout, would that destroy the open rear diff?

#18 85Sub4WD

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Posted 30 January 2005 - 08:15 PM

Have you read the section in the FSM on checking speedo calibration for on 1989 FT4WD cars? Subaru says yes, you will burn the CD on those cars if you spin one set of wheels and not the other for any length of time over 35mph, even for speedo testing. I know people who have ripped diffs on classics by doing burnouts on one wheel (or overheated them and locked the rear end so that it was basically a welded diff). The difference between that and running tires off the ground on a lift in a shop is that there is no resistance on them, whereas there is on the road.

#19 grossgary

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Posted 30 January 2005 - 09:12 PM

yes, i picked up crazyhorse's XT6. drove it around yesterday, runs great. how did you know?

i know of XT6's that have been towed improperly for some distance most likely over 35 and have yet to experience any problems, that's why i ask. one guy even took it to a trans shop and they said all looked well, but of course what can they really check without removing anything? (that was a MT).

#20 Seahag1978

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Posted 30 January 2005 - 09:39 PM

My owner's manual also tells me that for emissions testing, they can't put it on a 2 wheel dynamometer because it can cause serious transmission damage. My state uses them and Subarus are exempt from that portion of the test and perform only the basic two-speed idle tailpipe test. 4-wheel dynamometers are ok and won't do any damage.

#21 WJM

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Posted 30 January 2005 - 09:39 PM

I'd just drive it.

I talked to him...about 3 days after you got it as I was >< this close to buying it for the ER27T project. I know Tim personally.

#22 stngllhm

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Posted 30 January 2005 - 11:25 PM


So on a regular diff, open....if you sat there in...say a ford mustang, and did a one wheel burnout, would that destroy the open rear diff?


if you did it long enough yes. i know of quite a few diffs from trucks that people got stuck and sat in the mud pit with one tire spinning and toasted the diff




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