Auto speed steep downhill in L4 1st gear feels unsafe

[spacejase]

hello
I have a 2013 auto hilux which I noticed in very steep descents in l4 1st gear there was always quite a delay in the torque convertor locking up and it seemed to do so only after rolling without any braking for some metres (ie had to get the revs up) and once there was lockup there was still much less engine braking than manual 4wds I was driving with.

I found that I was rolling a lot faster than other cars in front of me and there were many sections where I had to use the (foot) brake, engine brake as well as the rear diff locker and was still rolling reasonably fast- is this normal? This felt unsafe

looking for possible solutions also

my hilux is low km and never towed, don't have any other issues with auto changing on the bitumen etc

thanks in advance

[Rob_Wood]

WOW, my 2004 model is way outta date. I didn't realise that hiluxs even had engine brakes, I thought that was reserved for heavy vehicles, and the diff locks I thought was only for use when playing a sticky wicket off road. I guess I'll have to do some more homework.
I hope you get some direction from those in the know, there seems to be a few knowledgeable people hanging around the forum.

[dave g]

Are you putting the auto in 1st before you start to go down the hill


I think he talking about engine compression ( don't touch the throttle)
Diff lock is to put more drag on the drive live if it picks up one wheel

[ptrl1600]

hello
I have a 2013 auto hilux which I noticed in very steep descents in l4 1st gear there was always quite a delay in the torque convertor locking up and it seemed to do so only after rolling without any braking for some metres (ie had to get the revs up) and once there was lockup there was still much less engine braking than manual 4wds I was driving with.

I found that I was rolling a lot faster than other cars in front of me and there were many sections where I had to use the (foot) brake, engine brake as well as the rear diff locker and was still rolling reasonably fast- is this normal? This felt unsafe

looking for possible solutions also

my hilux is low km and never towed, don't have any other issues with auto changing on the bitumen etc

thanks in advance

Hi spacejase,
I will assume that your Hilux is a diesel with the 4 speed auto? If so you have a A340 with a 2.8:1 1st gear, which is typical for a 4 speed. The manuals are 5 speed, so use a 3.8 to 4.4:1 1st gear depending on the gearbox, so will definitely have much better down hill engine braking. My V6 petrol Hilux also uses A750 5 speed transmission which has a 3.5:1 1st gear which I find ok for most down hill descents, but occasionally applying the brakes is necessary on the very steep hills. The best and probably most popular option is to fit aftermarket reduction gears in the transfer, but that’s not a very cheap alternative.
My last 4BY was a GU Patrol with 4 speed auto and it had the same issue, but I found that going down very steep descents was best done by rolling forward in reverse gear and controlling the descent with the throttle. This worked surprisingly well and provided I didn’t do it for a very long time, the transmission didn’t get too hot. However, I haven’t tried this method in the Hilux to date because the 5 speed seems to give enough engine braking to control the descent with minimal foot braking. I do know that in some cars, the Pajero in particular won’t allow you do it as the TCU goes into alarm, but it worked ok in the Nissan.

[spacejase]

I've a diesel 5sp auto

definitely in first gear

engine compression sorry not engine braking

diff lock in the rear

rolling forward in reverse gear amazing - I've never heard of that

I can measure my temps as I have an OBD scanner

[Gipsy]

Are you sure it's 5speed auto? Not sure they were in 2013 hilux diesel???

Anyway 1st gear won't have much engine braking at idle... The transmission needs a few engine revs to lock the torque converter

[ptommo59]

Hi spacejase,

Check but I believe the A750 autos only lock the torque converter in 4th and 5th and under specific conditions, so in your situation of 1st downhill any engine braking will be reduced by the amount of torque converter slippage.

On my 2012 SR-5 4sp I had a Wholesale Automatics Nomad Heavy Duty Valve Body and Lock Up Kit fitted for towing but one of its sales pitches was is it gives full engine braking downhill in all gears including 1st (With the Lock Up Kit only it will only maintain lock in 2nd up). Only issue I had with this setup is that it does not auto unlock so you have to remember to always press the button before coming to a stop or it either stalled the engine or made a horrible noise until you did.

[spacejase]

4sp

anyway terrible engine braking even when torque converter engaged

[Gipsy]

The joys of auto transmission, learn to live with it... So you have brakes for that
Auto is still the best for most other useful hilux purposes.

[Rob_Wood]

The joys of auto transmission, learn to live with it... So you have brakes for that
Auto is still the best for most other useful hilux purposes.

Always tried to stay in a manual for this reason. Also not a fan of the cost of annual service (auto vs manual).

[Gipsy]

Rob, annual service?? Why is an auto more expensive??

[Rob_Wood]

Rob, annual service?? Why is an auto more expensive??

I was always told that an auto needed to go (annually) to an Auto-Trans' specialist for a service (replace fluid, filter and check seals band tensions etc.) as well as having a general vehicle service every ten thou' or 12 months or so. A manual only needed to be looked at to check oil colour (viscosity etc) during the general vehicle service.
It'd be great to be told something different now after 40 something years of driving.

[ptrl1600]

Automatic transmissions have come a long way in the last 20 years or so with the advent of electrical control, overdrive and lock up torque converters and many models today have a "sealed" transmission that supposedly lasts the life of the car. Generally in heavy duty applications such as a Hilux for instance the transmission oil does need to be replaced or at least the pans contents replaced which may only be half of the total fluid contents. Not too many now even come with a dip stick to check fluid levels, so assuming you have no leaks and no issues, the fluid should last in excess of 50K km.
Late model transmissions generally use better synthetic fluids and run much cooler as a result of the lockup system, but I still like to replace mine at least every 40K km where as the older non overdrive units using "F Type" or Dextron ATF should be replaced every 20K, which for most people would be every 2 years or so.
With a manual gearbox, we would just check for water and the colour of the oil and in many cases it would last the life of the gearbox, just like the diff, so generally an auto is slightly more expensive to maintain, but I would argue that the fact we don’t need to replace the clutch and or duel mass flywheel during the life of the transmission compensates for that.