Ask the Car People.SM


4WD & AWD systems explained

1460 messages,  Last post on Sep 21, 2012 at 9:29 AM

You are in the SUVs Forum.

What is this discussion about? Chevrolet Suburban, Jeep Grand Cherokee, Subaru Outback, Ford Explorer, Nissan Pathfinder, GMC Envoy, Performance Mods, Tires, Suspension, Transmission, Truck, SUV

Messages Page 102 of 147

#1007 of 1460 AWD Noise by knobbyrobby

Dec 05, 2007 (5:38 am)

I have a 1998 Ford Explorer and it makes a weird winding noise when turning. At first I was thinking it was the power steering but my mechanic thinks its the AWD unit. It seems like my gas mileage has drastically dropped so I am also thinking its the same. It almost seems as though the AWD is constantly locked in because when you turn it also gets very rigid. Have you ever heard of this happening and is this possibly a recall item I dont know of. I'm sure it will be astronomical to fix this if it is the AWD...and the noise is driving me nuts. Not to mention I dont know if it dangerous to keep driving it like this or if it is doing more damge.

#1008 of 1460 Re: AWD Noise [knobbyrobby] by xwesx

Dec 06, 2007 (2:46 pm)

Replying to: knobbyrobby (Dec 05, 2007 5:38 am)
One easy way to distinguish between the steering or the AWD "whining noise" is to turn your wheels side to side while stopped. If you get the same whining, it is the power steering pump. Aerostar vans are notorious for whining power steering pumps. The pumps work fine, but they sure to whine about it!
 
As for AWD, I expect that the Exploder probably has a part-time, electronically controlled system. The Ranger has a switch-controlled electronic 4WD system that has all sorts of problems with the electronics. If the Explorer shares components in its system, it could be that the AWD is engaged all the time due to some system failure. Is there a light on the dash that will typically let you know when the system is engaged? As the system is part-time, it is likely hard on it to be running on dry pavement, etc., due to the lack of slippage available. If you turn hard at slow speeds, you should be able to feel the truck "binding" a bit and likely hear wheels slipping as the system relieves pressure. Try it on a gravel surface so the wheels will let loose easier.

#1009 of 1460 Re: AWD Noise [xwesx] by knobbyrobby

Dec 06, 2007 (8:08 pm)

Replying to: xwesx (Dec 06, 2007 2:46 pm)
What really happens is when you're driving it feels like the feeling you get when engauged in 4 wheel drive. The steering gets rigid and jumpy. Especially when on the highway and you hit a bump doing like 55-65 MPH. The whole front end gets a massive vibration and pulling. It also feels like the steering wheel is drifting side to side. I firmly believe its the AWD locked in constantly....although it started gradually happening and stopping but now doing it all the time. It feels very dangerous and my gas mileage is terrible. I'm sure this is a ridiculous price tag to fix if not a reacll item.

#1010 of 1460 Sienna AWD by ateixeira

Dec 07, 2007 (9:54 am)

I know they used to have a viscous coupling, but can anyone tell me what Toyota is using for the current models?

#1011 of 1460 1996 Jeep Cherokee Won't Disengage 4WD by chris301

Dec 08, 2007 (4:08 pm)

I have a 96 Cherokee. Only recently have I had the need for 4WD. I have heard a faint whining sound when engaged in 4WD and driving, that stops when the car stops. Now, the car seems to be in 4WD, even when I switch it back to 2WD. After a bit, I'll hear a "thud" and can feel it disengage, and then I am definitely back in 2WD. What's happening here? It's only happened twice, both today. Its cold and snowy where I am. I don't want to ruin anything. Any thoughts?

#1012 of 1460 Re: 1996 Jeep Cherokee Won't Disengage 4WD [chris301] by xwesx

Dec 08, 2007 (6:47 pm)

Replying to: chris301 (Dec 08, 2007 4:08 pm)
It is probably worth your while to check the fluid levels in both the transfer case and the front differential. If you have never replaced it, consider doing so now. It sounds to me like something is binding a bit - probably in the transfer case - and preventing the system from disengaging. Also, are you engaging and disengaging it properly? Some of the "older" shift-on-the-fly systems (not sure if Jeep falls under this classification) required a short jaunt in reverse to allow the transfer case to disengage, even though you can shift into 4WD while traveling forward.
 
Any problems with it engaging at the time you request it?

#1013 of 1460 Re: 1996 Jeep Cherokee Won't Disengage 4WD [xwesx] by chris301

Dec 08, 2007 (7:11 pm)

Replying to: xwesx (Dec 08, 2007 6:47 pm)
Thanks much for the reply. I've had no problem engaging whatsoever. I'll replace the fluid tomorrow. I'll try reversing first to disengage as well and will post results.

#1014 of 1460 Good place to discuss AWD differences by kurtamaxxxguy

Dec 11, 2007 (10:27 am)

Glad to have found this forum as I have some AWD queries:
 
1. Is it possible to change the Subaru Outback auto-trans AWD bias ? I understand it is RWD-biased and perhaps that is why the car has a reputation for spinning out (per CU and some other tests I have read) ? Would be nice to be able to readjust it to prevent that.
 
2. How does the RAV4's AWD compare to the Outbacks? It seems the RAV4 is reactive, save for a user setting that offers full AWD for speeds below 20 mph.
 
I'm also curious if VW has abandoned the torsen based Quattro and is now relying on Haldex, and how the Haldex system compares to that used in the Subaru.
 

#1015 of 1460 Re: Good place to discuss AWD differences [kurtamaxxxguy] by ateixeira

Dec 11, 2007 (2:25 pm)

Replying to: kurtamaxxxguy (Dec 11, 2007 10:27 am)
I'll take a shot at trying to answer each question.
 
1. Not really, though you can insert a FWD fuse to send all power to the front axle. Note that this is for temporary use only, such as when you get a flat tire.
 
2. I was bummed that Toyota took away the full-time system that existed in prior RAV4 models. The new one is part-time, on-demand. At an event Toyota hosted themselves, the AWD system failed to climb a hill they had picked for their press demo:
 
http://www.drive.com.au/Editorial/ArticleDetail.aspx?ArticleID=11004&vf=23
 
VW: Haldex makes what is probably the quickest reacting AWD system on the market, but it's still reactive. Volvo and Ford also use the same supplier for their systems.

#1016 of 1460 Re: Good place to discuss AWD differences [ateixeira] by xwesx

Dec 11, 2007 (6:17 pm)

Replying to: ateixeira (Dec 11, 2007 2:25 pm)
The AWD on the Subaru automatic actually defaults to a FWD bias, though it can shift to rear depending on the traction situation, as much as 80-20 either way. But no, it is not driver controllable. The STi has a driver-adjustable system, at least on the new model.

Messages Page 102 of 147

To POST a message, please Sign In.

Advertisement

Browse by Category

Browse by Vehicle
   View All Vehicles

Browse by Board
Browse by Topic
View All Topics

Edmunds Community

Advertisement