Unable to rev engine

So I was recently in Idaho on a hunting trip and was driving up a fairly steep dry road with a more rounded style rock golf-softball size I was in 4high and in first gear truck did fine. Got about half way up and there was a little bench in the road so I stopped and shifted to 4 low and first gear as the road ahead got really steep and rockier. I again stepped on the gas and at the worst spot in the road the tires were just spinning on the rocks and I lost my fwd momentum and came to a stop. As I assessed the situation I tried stepping on the gas to try to keep going forward but the engine would only rev up to 1200 rpm barely more than idle even though I even tried pushing the pedal to the floor. So then I tried turning the different nannies off one at a time and still won’t rev above 1200 rpm in any mode. I put the truck in park and neutral and it revs fine. I still don’t understand what was happening and am hoping to gain some knowledge on the subject. I ended up just backing down the hill and then tried revving in 4 low and everything worked fine but I didn’t try the hill again as I was alone and didn’t want to risk a breakdown. Thanks for your help
Bill

 

It’s normal, 4 Lo has throttle limits.

 

Doesn’t seem right to me. That rpm won’t even move the truck. It was going up the hill for about 100 yards at much higher rpm spinning the tires until I spun out. Then once I was sitting there stopped nothing worked to even spin a tire

 

HPTuners or OVT can remove that annoying safety issue...I agree, very annoying when you need it!

 

Well that explains why my RPM peaked yesterday at around 2,500 coming up my steep drive pulling a travel trailer in 4lo S3.

 

Is there a way to get around it in a bad situation? Maybe going to 4 hi then back to 4lo ? Thanks for any insights

 

Has anyone on here personally, successfully fixed this issue through a tune? OVT, HPT or other?

I have Overland Tailor's "Overland Torque Tune" on my '17 which did not solve the issue for me. I purchased it specifically to address this issue and let them know what I was trying to fix beforehand.

I know the tuning software has access to various 4 Low parameters but some have suggested that messing with those doesn't actually do anything.

 

Correct, the tunes do not do anything when you drop into 4Lo. I tried messing with all sorts of parameters with my HPTuner.

The only way I got around it was to make a device that tricked the 4WD ECU into thinking it was still in 2wd and then modifying the Tow/Haul button with a considerably more open throttle. Tow button is programmable but only works in 2wd.

Toyota put the limiter there so you don’t end up breaking shit. First thing to snap will be the CV axles and if you get lucky you’ll snap the stub shaft inside the front diff. At the end of the day the only real way to resolve this is with a lower geared aftermarket transfer case, which is the route I’m taking, which will crawl up with little help from the skinny pedal.

 

Odd, I’d thought that you could alter the rev limiter/speed limiter in Lo Range via HP Tuner. We increased my rev limit about 5% to 6,300 when dyno tuning my truck, but I haven’t messed with Lo Range specifically.

@snivilous has a lot of experience with HP, and I’d thought he mentioned something along these lines. Let’s see if he chimes in with some insight.

 

@Cruzer knows more than I. Besides maxing out all the throttle angle allowables, nothing else to do. And Cruzer has put his truck into situations requiring that much torque much more recently than I, so I have no doubt what he says.

The throttle angle limits are a maximum cap, doesn't mean the truck will actually use all of that though. At least that's my understanding. Other variables at play we don't have access to.

 

I recall OVT being able to remove speed limiters in 4Lo...it was an option if asked for...it can be done but as stated...you ain't sendin' it unless your bendin' sh!t! Same with reverse if I recall...limits can be removed.

Might be one of the limiting factors when comparing VHT to HPT...