Possible damage from over rev in 4 Low?

Greetings everyone, I’ve read many a thread here but never posted. On a recent ski trip the house we rented had a very steep windy driveway covered with snow/ice. I put the 4Runner in 4 Low thinking I needed max traction (in hindsight more initial speed and 4 high might have been better)…but long story short I got half way up and starting slipping backwards. I realized I needed to slow the tires down and was able to gain a bit of traction and eventually made the climb up to the main road…but not before I spun tires and probably over revved the engine in 4Low for a good 30-60 seconds a few times. I did not happen to check the tach in the heat of the moment but I’m sure it was faster than intended for 4Low. This was probably a month ago now, I’ve never had any warning lights on the dash and vehicle seems to run fine, but I do feel like I’m getting a faint burnt smell now when I turn off the vehicle. Did I toast the transmission fluid? Not sure if I need to flush it and replace or if I may have done other damage? I realized one thing thru this that I definitely needed to educate myself more on 4High/4Low. Appreciate your feedback! Thanks.

 

My guess is that you’re probably fine because you were going uphill, so engine revs were “under control” of the throttle. That means, if you actually did hit redline, the engine would have been able to protect itself with the rev limiter. You should have heard the engine bounce of the rev-limiter if you think the revs went too high.

It may have been a different story if if you were going downhill in 4lo. Downhill, the wheels speed could potentially force the engine to over-rev, regardless of any rev-limiter activation. Kind of like if you were in a manual transmission car and shift from 6th to 2nd…the engine would over-rev because of wheel speed, not throttle.

That said, no harm in changing out engine oil and doing a pan drain/refill on the transmission. It was well earned It also would give you a chance to look at the engine oil filter, and see/smell the transmission fluid.

 

The limiter protects the engine but if you live on it you will eventually cause damage but that's like ricer style.

It's fine.

 

First, I highly doubt you did any damage to the engine. The ECM will prevent you from over-revving it.

As far as 4Lo providing "more traction" though, that is incorrect. You have just as much traction in 4Lo as you do in 4Hi. You have more wheel (and usually vehicle) speed in 4Hi. 4Lo is a gearing change only.

 

Rapidly spinning your wheels will not get you unstuck. The friction actually melts the snow or ice a little and it’s like you’re riding on watery ball bearings.

 

This! Man this is a perfect illustration

 

Welcome from Arizona!

 

Absolutely agreed. But when you need to have some vehicle speed - say, like taking a run up an icy hill - 4Hi will give you the speed you need to make it over. Of course, this also assumes that you're smart enough not to break traction and keep it firewalled on the way up.

 

Yes, in the case of uphill on slippery deep surfaces, like snow or sand, momentum is your friend.