The other day while driving in slush, I decided to try 4WD. But it seemed like the power was nearly cut in half. I haven't had a chance to drive in snow more than just an inch or so and the tires are getting to the pavement. So I was wondering if a difference in tire circumference could be the cause. The fronts are new, but the rears are a little more worn, but not too much more. The car is an 89 GL wagon with 4WD and SPFI. I haven't had a chance to check the circumference of the tires to see what the difference really is due to too much rain and slush. I wouldn't think the ECU would be programed to cut the power while in 4WD. What fun would that be?

Tire circumference can have an impact, but I wouldn't expect a minor difference to show up so pronouncedly in slush. Maybe the difference isn't minor, like different brand/models (same nominal tire size doesn't mean same circumferenece), or maybe wrong rear diff ratio...

Check the rear diff oil. If its low it could be causing some binding. Same with the tranny.

which 4wd system do you have? If you have a single range 5-speed, you could have a vacuum leak between the solenoid and the diaphragm.

It has high and low range and a five speed. It looks like it might snow today so I may get a chance to run in 4WD in at least deeper snow. This car has never been off road in its life. Not even a slight scrach on the skid plate. Maybe I should take it out in the mud someday.

maybe it wasn't enough slush for the tires to slip and you were feeling the transmission bind. if that were true, it would feel bogged down the more you turned the steering wheel, but should be fine driving straight as an arrow. was it all the time?

 

agree on tire check too.

tire check and also check alignment. Is it hard to get into or out of 4wd?

I checked the tire circumference and found the fronts to be 1 inch larger circumference than the rears. Then it started to snow. "YES" On the way home from work I got into about 2 inches of snow, not as much as I had hoped for, but things were fine as long as I stayed out of other tracks. I love my Subaru. I could have had a lot of fun if it weren't for the non Subaru oweners going so slow. So it looks like an inch of difference in circumference from front to rear is too much. However it goes really good in the snow. Thanks for your input.