general fwd question

[johnc]

Hope you experts won't mind a generic question [91 Tercel 207K, 4sp]:

 

Mechanic warned me to fix a front wheel bearing at inspection in Nov., so I stopped using the car until I could clear an indoor space to do it [Pocono winter]. Now that I'm ready, we've both forgotten which wheel it was!

To find out, I lifted each wheel separately but felt no 12-6 o'clock play. He had warned me sometimes you can't tell that way, and thought his diagnosos had been made after running the car on the lift. So next I put the front end on blocks and drove the wheels in 2nd gear, I think. Very localized, continuous noise immediately showed pass. side was the one to replace!

Strange thing [for me] was, however, that after about a minute, maybe less, as the engine speed dropped [engine was initially cold, so warming up a bit?] the driver's side wheel slowed and stopped altogether, while the pass. [bad] one continued to spin seemingly quite fast. I could rotate the driver's side wheel by hand, even spin it a bit, i.e., little resistance, but it soon came to rest again.

 

PLease can someone explain to me what's happening here?

[RallyKeith]

It's just the physics of an standard open differential. It only truely puts power the wheel with the least resistance. For what ever reason there is less resistance in the passangers wheel transmission path than the drivers. If you were to go and try to stop the passangers wheel you would easily get it to stop and the drivers wheel would start spinning. It's a matter of how "tight" all the components are, including the wheel axles shafts, bearings, and brakes. Bad bearings are usually loose and would would imagine that with no load on them should appear to spin more freely.

 

Hope this helps somewhat.

 

Keith

[idosubaru]

FWD = one wheel drive

and 4WD really only = 2WD

 

unless their are limited slip type systems involved that's the way it works as he just mentioned.

[CNY_Dave]

FWD = one wheel drive

and 4WD really only = 2WD

 

unless their are limited slip type systems involved that's the way it works as he just mentioned.

 

A 4wd-auto/awd-auto trick- if you hold the brakes on, apply throttle, and quickly take your foot off the brakes, then quickly take your foot off the gas and stomp back on the brakes, you get a brief moment of gen-u-ine four wheel drive. You get back on the brakes quick to keep that inch of progress you just made.

 

Essentially, the torque that it takes to drive the 'free' wheel up to speed (especially since when you lock one wheel of a differential the free wheel spins faster) is also applied to the wheel with traction, for that brief moment before the free wheel spins up.

 

Progress can often be made, but will be somewhat slow. This works really well if you are in a spot where rocking it will help, and you get a bigger gain each time you switch direction.

 

 

Dave