Be Careful! It may not downshift to first.

[OsoCruiser]

I just discovered a quirk in the transmission that everyone should be aware of. I was pulling my 23 foot, 5000 lb travel trailer in the southwestern Colorado mountains. On a long, straight, steep downhill grade at 40 in second gear, I approached a 25 mph curve. When I tried to shift into first, all I got was a beep. It would not go into first until I braked to 23 mph! This speed corresponds to only about 3100 rpm in first. When towing on long downhill grades I like to use engine braking as much as possible to save the brakes.

None of the other gears behave this way. Use of power mode on the transmission did not help. It performs the same in low range, but did not seem to be as much of a problem there.



Otherwise the truck was an excellent tow vehicle and performed great on 4x4 trails too.

 

[bjowett]

Time for Tundra rotors and calipers, perhaps?

 

[2000UZJ]

it's not a quirk, it saves the engine from downshifting into a lower gear and blowing up. My 100 Series wont't go into 1st gear until I hit 33mph/3100 RPM. Best way to figure out your gearing it to manually shift it in town and familiarize your self with the sounds,revs, and shift points. therefor when you tow you know what speed you need to be at going into another gear and where your power band is to stay in it as long as possible.

 

[JBHorne]

This is in the manual and it will not shift unless the lower gear will be under 3100RPM.

 

[Carl L]

Time for Tundra rotors and calipers, perhaps?

Would be a pointless change, they're practically the same. 100-series would see the benefit.

 

[OsoCruiser]

JBHorne, it seemed like it only happened when trying to downshift to first. I'll have to check it again.

 

[pman]

it's not a quirk, it saves the engine from downshifting into a lower gear and blowing up. My 100 Series wont't go into 1st gear until I hit 33mph/3100 RPM. Best way to figure out your gearing it to manually shift it in town and familiarize your self with the sounds,revs, and shift points. therefor when you tow you know what speed you need to be at going into another gear and where your power band is to stay in it as long as possible.

I thought 29 was the magical downshift speed on the 100.

FWIW every late model Toyota/Lexus that i have driven behaves similarly. They wont shift into first until you drop below a certain speed/rpm........it really pisses me off sometimes, especially since i drive a real manual regularly.

 

[2000UZJ]

I thought 29 was the magical downshift speed on the 100.

FWIW every late model Toyota/Lexus that i have driven behaves similarly. They wont shift into first until you drop below a certain speed/rpm........it really pisses me off sometimes, especially since i drive a real manual regularly.

29 is upshift/maximum kickdown speed in "D"

 

[bjowett]

13.9" vs 13.4". More is more.

 

[GordJ]

I just discovered a quirk in the transmission that everyone should be aware of. I was pulling my 23 foot, 5000 lb travel trailer in the southwestern Colorado mountains. On a long, straight, steep downhill grade at 40 in second gear, I approached a 25 mph curve. When I tried to shift into first, all I got was a beep. It would not go into first until I braked to 23 mph! This speed corresponds to only about 3100 rpm in first. When towing on long downhill grades I like to use engine braking as much as possible to save the brakes.

None of the other gears behave this way. Use of power mode on the transmission did not help. It performs the same in low range, but did not seem to be as much of a problem there.



Otherwise the truck was an excellent tow vehicle and performed great on 4x4 trails too.

With the engine braking increase in efficiency in low gear the possibility of pushing the tow vehicle is greatly increased. With the brakes, the ABS and traction control would be active and your wheels would not be locked up. The engine braking could have the effect of locking your wheels and you would have no control over your truck.
Its not a diesel, there is no engine brake, so you have to use the brakes when you have to slow down.

 

[pman]

With the engine braking increase in efficiency in low gear the possibility of pushing the tow vehicle is greatly increased. With the brakes, the ABS and traction control would be active and your wheels would not be locked up. The engine braking could have the effect of locking your wheels and you would have no control over your truck.
Its not a diesel, there is no engine brake, so you have to use the brakes when you have to slow down.

One of the greatest things about engine braking is its impossible to get the wheels to lock up......unless you stall the engine, but the torque converter will prevent that. You can make them skid on a slippery surface, like ice, but the wheels can't fully lock like they can with the actual brakes. In this case though, there is no way to get the wheels to lock up while engine braking......maybe skid a little on ice, but since he's in AZ, not really a concern and still not likely nonetheless.

Also gas engines have better engine braking than diesels.......that is unless you add jake brake......which the 1VD does not have......it doesn't have an exhaust brake

Compression release engine brake - Wikipedia, the free encyclopedia

 

[Tucan viajero]

You can make them skid on a slippery surface,

Which is precisely why the target rpm in 1st must be quite low.

The reason why the automatic transmission doesn´t allow for downshifts that would result in very high rpm in 1st gear, is precisely because skidding is a possibility, and a quite dangerous one, if it happens at the wrong place or time.

This problem is a lot more serious in vehicles equipped with automatic transmissions than in vehicles with manual transmissions, despite the fact that these can downshift at any speed. This is because their drivers usually are not as aware of what is going on or what they are doing. It is just too easy to mindlessly pull on the lever to downshift not knowing what will come next. Driving a manual invokes more driver involvement.

UA, with almost 100% automatic transmission driver error occurrence, is a good example of that.


tv

 

[GordJ]

One of the greatest things about engine braking is its impossible to get the wheels to lock up......unless you stall the engine, but the torque converter will prevent that. You can make them skid on a slippery surface, like ice, but the wheels can't fully lock like they can with the actual brakes. In this case though, there is no way to get the wheels to lock up while engine braking......maybe skid a little on ice, but since he's in AZ, not really a concern and still not likely nonetheless.

Also gas engines have better engine braking than diesels.......that is unless you add jake brake......which the 1VD does not have......it doesn't have an exhaust brake

Compression release engine brake - Wikipedia, the free encyclopedia

I always get effect and affect confused. I was trying to say that the result of the tires turning slower than the truck was travelling could be a loss of traction.
I agree completely that the wheels will not "lock up" but going into low gear with a trailer pushing you around a tight corner could possibly cause a lack of control.
The OP was commenting on what he thought was a quirk in the transmission and I don't think the fact that he is in AZ is relevant as Toyota can't program the transmissions differently for AZ and AK.
I am not sure what it is like in AZ but we find that with sand or gravel under the tires, on or off the pavement, traction can be compromised and a loss of control can result.
As far as engine braking, to slow 9000 lbs from 40 to 25 MPH on a steep incline with the engine seems to be beyond the realm of common sense, whether it is gas or diesel.