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problem with four wheel drive

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On slick surfaces, if I put my 91 Loyale, manual transmission into four wheel drive, it begins to skid if I go above say 30 mph.

 

It kind of feels like to me that the rear is trying to pull to the right, looses traction and swings back to the left and repeats. But I might be wrong. If I disengage four wheel drive, it drives straight, much different feeling and can drive faster, up to the limit of my caution.

 

What could be going on here? The only time I can use four wheel drive is in deeper fresh snow before it gets packed down when I am limited to slower speeds anyway.

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define "slick surfaces" rain? or ice?

 

are the tires all the same, with tread depth that is the same?

it sounds like the rear tires are a little smaller than the front's causing it to drag the back end.

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Slick surfaces - Ice, or packed snow. Slick enough to spin the tires moving forward from a stop.

 

I think the tires are two different sizes front and back - I don't recall which is smaller. But I've rarely had tires that are the same front and back and have not seen this happen before. The worst that I've seen before is that four wheel drive just doesn't show much if any of an improvement over front wheel drive.

 

Should I try switching front and back to see what happens?

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Larger tires in the back would make the back "push" more.

 

Check the condition of the rear trailing arm and swing arm mounts. The rubber bushings can shift moving the rear wheel alignment.....if the mounts have shifted outward....this will cause outward toe on the rear wheels....another contributor to the "pushing" feeling.

 

Alignment of the rear wheels can help, but replacing the bushings is usually the only full solution

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No, you should put the same size tires on ALL 4 corners. :rolleyes:

 

+1

The 4x4 wont work properly if the tire's are different sizes, because if the fronts are bigger or smaller than the rear, they are trying to travel at dfferent speeds. This is also very bad for the 4x4, if you were in 4x4 and hit a dry surface at speed, you will break something. If you're lucky it will just be a C/V if you're not, it will be the transfer gears inside the transmission.

 

Luckily R13 tires can be pretty cheap on Craigslist, I see full sets with good tread for around $50 all the time.

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And if it still persists once you have all tires the same, you then need to find yourself another rear differential. An open slip differential will be more flexible to different sized tires between left and right. You won't be able to find a limited slip differential anyways.

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And if it still persists once you have all tires the same, you then need to find yourself another rear differential. An open slip differential will be more flexible to different sized tires between left and right. You won't be able to find a limited slip differential anyways.

 

Why would he need a new diff? And If he did, why couldn't he find a limited slip? There were many made, both viscous and clutch type. Not really an issue though, since he doesn't need a new rear diff.....not at all.

 

IF it's not the tires, it's the rear alignment. I've had it happen to my car before, and corrected it by installing new bushings, and realigning the rear end.

 

Sometimes the 3 bolt holes on the trailing arm need to be "ovaled" a bit to get the proper alignment.

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I know that the accepted wisdom is that all four tires must be the same, and perhaps that's ideal, but I have run different tires front and back with no problem before, as I mentioned and since I use four whell drive sparingly, I'm not likely to go out and buy another set of tires. I usually buy used tires in pairs from the junkyard - if i could find a full set of good used tires .. but I never have.

 

I'm tending towards the bushings and alignment theory, but i don't know whether I will be able to work on it before the weather gets better. If I do, I'll let you know how it comes out.

 

Thanks for the thoughts.

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The two tires in front are the same, as are the two in the back? For testing, you could swap one front and one rear tire, as long as you don't have a LSD rear end. This will make the front to rear ratio the same. The car might pull to the side a bit.

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Why would he need a new diff? And If he did, why couldn't he find a limited slip? There were many made, both viscous and clutch type. Not really an issue though, since he doesn't need a new rear diff.....not at all.

 

IF it's not the tires, it's the rear alignment. I've had it happen to my car before, and corrected it by installing new bushings, and realigning the rear end.

 

Sometimes the 3 bolt holes on the trailing arm need to be "ovaled" a bit to get the proper alignment.

 

When he disengages the rear differential, then he says that there is no problem. If it was just a rear wheel alignment issue, it would seem like the problem would persist when the rear differential is disengaged.

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it doesnt engage the rear diff, in engages in the trans. he wouldnt notice it in 2wd since they can spin at whatever speed the car needs. once he engages the front and rear must spin the same or one will have to slip.

 

limited slip wouldnt be any different than open, its still (generally) 1 tire that spins, just the traction tire instead of the slipping tire like an open.

 

it could be a diff problem if he has one of the different gear ratio rears, but its unlikely (that said, might be worth checking the sticker on the rear...)

 

my votes for tires. they are the biggest performance upgrade you have, at least go to a decent used tire shop and get some matching ones.

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Tires that are different front to back combined with the natural tendency for a 4WD to slide out on ice in tight corners are the likely causes.

 

A centre diff makes all the difference on ice.

 

Rob.

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When he disengages the rear differential, then he says that there is no problem. If it was just a rear wheel alignment issue, it would seem like the problem would persist when the rear differential is disengaged.

 

When they aren't driven, the rear just trails behind, doesn't try to do walk out from behind. Just by nature the rear end can't "push" out, because it's being pulled.

 

Also, there is another layer to the condition.

Disengaged, the rear wheels aren't putting any power down to the road, they are just trailing behind, "pulling" on the rear arm bushings.

 

When powered, thy trailing arm "pushes" into the bushings, thus pushing the vehichle forward. When the bushings are very worn and shifting, It changes the actual alignment slightly, and could multiply the effect of the "ghost walk".

 

This same issue is actually a problem in the newer 05-08ish model Outbacks. In that case it's also an alignment issue in the rear end, corrected by different specs/bushings in late production.

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The two tires in front are the same, as are the two in the back? For testing, you could swap one front and one rear tire, as long as you don't have a LSD rear end. This will make the front to rear ratio the same. The car might pull to the side a bit.

 

Yes, the two in front are the same and the two in back are the same. I could try this and see what happens; how do you know if you have a limited slip differential?

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Yes, the two in front are the same and the two in back are the same. I could try this and see what happens; how do you know if you have a limited slip differential?

 

This works for part time 4WD trannys. Make sure it's out of 4WD, then jack up one rear tire and try to turn it by hand. If it offers little resistance you have a regular (not LSD) diff. If you can only turn it a little way, try putting a wrench on a lug nut and turn it more. If I recall the stock LSDs are set to slip at around 60 ft-lbs. If you still can't turn it maybe you're in 4WD or you have a full time 4WD tranny.

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I would look at tire size and condition. Secondly, alignment. I have seen it before. You will never get the full potential without out those tires trued up and accurate. You may have to replace parts to get the alignment accurate at times.

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easiest way to tell if you have an lsd (besides the sticker) is to jack up the back end and spin a tire by hand. if the other side tire spins in the opposite direction then its open, spins int he same direction then its limited slip.

 

always good to know, but unlikely to make a difference in your issue.

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