Couldn't reverse over a rock

I'm out on a trail.. I have a very heavy camper rig. Automatic transmission.

I had levelers behind my wheels, and was trying to back up on to them. (if you don't know what levelers are, think of it as a 4" tall rock.

I floored it, and it would not back up onto them. The engine spun up, though not to high RPM's. I didn't push it that way for long, but after several seconds of flooring it, it would not back up... I quit and drove forward onto them.

I'm worried though, that something might be wrong.
Is reverse very weak, and this is normal? And if not, any ideas what the issue could be?

If it is normal, would putting it into 4lo have helped? I was in 4hi.

thanks for any advice!

 

I don't know if it's normal ( I have a manual trans, not an auto.) Doesn't sound like it. But then, how heavy is "heavy"? 2,000 lbs overweight? How big are your tires?

4 LO certainly would have helped. Why didn't you try it?

Tell more about your truck -- what engine in it, 2.7L or 4.0L?
How many miles on that engine?
Any other drivetrain / driving-related issues come to mind in the past 25K miles / 2 years or so?
Maybe the ATF (transmission fluid level) is low or has gotten low for some reason.

 

4lo would have helped. These trucks aren't geared very low in 1st or reverse. Especially reverse. Pulling forward a few inches and hitting the levelers with a little momentum might have done it too. I'd have built up a ramp with rocks, boards etc. so the climb was more gradual.

 

https://www.caranddriver.com/toyota/tacoma/specs

 

Because passenger trucks have offset bevel differentials the force to reverse is much greater.

Basically it’s like opening a door by pushing by the hinge instead of by the handle.

This is normal and 4lo will fix it.

 

Thanks everyone, that was fast! Turned starlink back on for something else, and didn't expect the replies already.
Truck is 4.0 liter
125k miles
No other problems.. It has enough power in forward to tear the differentials apart (mistake I made once).
The weight...... Max I've weighed it is 7760lbs!!
But, this thing has been w/ me on very rough trails, steep mountain passes, etc. That's where I am now. And no other problems.. This is just the first time I've noticed this reverse issue.
My fear is that I'll be down a steep road and unable to turn around.. Then unable to reverse up it! But if 4lo would help... great.

I don't know why I didn't try 4lo.. Other than simply driving forward onto them was an easy option.

 

If that's a real scale weight it's the heaviest I've ever heard of a Taco being.

If I was you I would do some test runs in reverse 4LO up various grades w/ various soil/surface types to see what the truck's limitations are in that regard.

Bearing in mind as well that, as others have pointed out, the diff isn't quite as strong in reverse as it is in forward motion.

 

Gilbert, there's an overweight tacos thread somewhere here, and I'm surprisingly not the heaviest (but am definitely up there). The pop-up camper I have is basically made for tacos, and everyone w/ one has a truck of similar weight. (four wheel campers 'fleet' camper)
Good idea on testing various grades.

To anyone, I'm curious.... What is spinning in the transmission or engine, in this situation? The motor ran at about 1500-2k rpm's, sounding a bit weak.. But didn't bog down and die.
I know in a manual transmission, it would be the clutch.. is it basically the same sort of thing in the auto trans? some slip surface? And does it wear out?

 

Auto trans has a "torque converter" in it which is a fluid-filled mechanism with no direct contact between the torque-transmitting parts. I.e. it is the pressure of the fluid itself pushing against vanes/baffles inside the torque converter where the work happens. The consequence of forcing it to spin when the wheels can make only limited (or no) movement is that the fluid in it starts to heat up.

I'm not sure how long it takes the fluid in an automatic trans to overheat if the engine is driving, say, 3K rpms into it with the transmission basically locked up due to lack of wheel spin. I wouldn't gun it for more than 2-3 seconds max in that condition.

 

Here is all you could probably ever want to know about a torque converter, if you've got 45 minutes to spend:

https://www.youtube.com/watch?v=uXgSttKLsHs

 

Reviewing this video, around the 8:45 time mark, "stall speed," it would seem likely that the combination of your super-heavy truck & the steepness of the leveling block caused the engine to hit its "stall speed," i.e. the highest rpm the engine can achieve when the wheels + back half of the TC cannot move. Basically it's the max torque the TC can produce. Any additional torque requested of it beyond that just gets converted instantly to heat through massive turbulence in the fluid.

The narrator also suggests that the temperature rise in the ATF (trans fluid) inside the TC is around 10ºF per second when it is stalled (locked up) on one side but receiving max engine input on the other side. Normal operating temp for an auto trans might be somewhere between 190º-210ºF. Bad things start to happen when ATF exceeds 250º-ish F even for a short time, some people say above 240ºF.

 

Or just pulled in. I mean, you can’t see the lake at night when you’re sleeping anyway….

 

I think if you try this specific move -- backing up onto 4" tall levellers -- in 4LO, the truck will have no problem, even at nearly 8,000 lbs gross mass.

But yeah you are well outside a reasonable comfort zone being more than 2,000 lbs past the GVWR. I'm not saying this to harp on you, just to alert you that in that condition the truck is much closer to many of its component strength, performance, and handling safety margins than your average 5800-6000lb "heavy Taco."

 

Hi,
Back from the trip. No problems!

I know, the weight is not good. The weight I mentioned is fully loaded at the start of a trip, with passengers, with over two weeks of food and water and everything.. We lose over 1000 pounds over the trip. It's about 6000 lbs, unloaded. (But it's never 'unloaded'.. I only use this rig for camping)
A lot of the truck has been upgraded... Differentials, UCA, LCA, suspension, leaf springs, brakes, master cylinder... More I'm not thinking of at the moment.
And I do drive carefully.. Never over the speed limit. Plenty of distance between me and the vehicle in front of me.
On the trails, I crawl... I go way slower than I need to. I have my house on my back, and don't want to shake up all my belongings.
The weight of the vehicle is always on my mind.

 

I use 4lo in any reverse situation when towing or carrying a heavy load in the bed.
My friends and brother call it overkill, but I think it is worth the extra 10sec.