mjwalfredo

I've got a 97 4Runner limited getting up there in the mileage department. It's got the A340F transmission. For the past 2-3 years it has been reliable but hadn't felt very "drivable". I thought maybe my transmission was getting ready to kick the bucket but it was strange because the "drivability" issues did not get worse over time.

Fast forward to yesterday. I finally got around to doing a drain and fill of the transfer case oil and I am so glad I finally got around to it. Afterwards, there was a noticeable improvement in the "drivablity" issues. I didn't do any other maintenance accept for the transfer case. Here is what improved:

1. Going from coasting to getting on the gas and vice versa is much smoother now.

2. A clunk that would happen when coming to a complete stop has almost gone away completely.

3. Shifts and general acceleration are both smoother. The truck used to surge forward when shifting to the next gear gear and that has almost completely gone away. The shifts don't feel nearly as jerky anymore.

4. Going from drive to reverse and vice versa is much smoother.

So, I find this all very interesting as it was pretty much dumb luck that a drain and fill all but cured the truck's issues. The oil level might have been low but I didn't think to check the level before the drain and fill. Would a low transfer case oil level cause the problems I had experienced? It also could be that I had used walmart brand 80-90 synthetic gear oil. What seems more likely to have been the cause of the problem?

Also, I was amazed that doing something to the transfer case would have such an effect on 2wd mode. I was wondering if someone could explain what goes on in the transfer case when in 2wd mode. Why would the oil make such a difference in 2wd mode and what exactly happens in the transfer case when going from 2wd to 4wd with this truck?

Thanks!