Numpty Transmission Question:

[BobMurphy]

I don't have a User Guide for the 2001 HDJ-100 'VX' so maybe someone can enlighten me .

I have the 4-speed Auto, it also has an Overdrive.

I have no idea which gear is selected at any time so I was wondering if the Overdrive is actually the 4th gear ??

So, is it actually a 3-speed with Overdrive ??

Someone will know .

Thanks.

Bob.

 

[Gav Peter]

I believe that's right Bob - I seem to recall JW discussing this in the past... Bit surprised he hasn't been in to tell us by now; he must have another 'orse riding lesson

 

[Chris]

Yes, Bob. Correct.


Someone will know.

We all thought it was you!

 

[Jon Wildsmith]

So, is it actually a 3-speed with Overdrive ??

I believe so. www.mudtoys.com/manuals/100/05rm.pdf is the main repair manual with some gearbox basics and www.mudtoys.com/manuals/100/08erm.pdf for the diesel engines.

 

[BobMurphy]

Someone will know.

We all thought it was you!

Well, when I've finished repairing all the neglect I'm finding under the 'new' 100 I might be in a position to answer questions (It took a lot of work before I was familiar with the 95) .

Expensive things Learning Curves, aren't they .

Bob.

 

[BobMurphy]

Yes, Bob. Correct.

Thanks for the replies . . . .

So, it isn't an "Overdrive" at all, its a 4th gear.

On all the previous cars I've had with Overdrives (Sunbeam Rapier, Humber Sceptre Estate, Series III LandRover) the Overdrive is a separate gearbox that raises the ratio of the main box (only works on 3rd & 4th on the Chrysler cars as it needs oil pressure to work).

I guess there's no point in switching in and out of O/D when towing then as it doesn't give the lower gears an easier time.

Interesting.

Bob.

 

[Jon Wildsmith]

So, it isn't an "Overdrive" at all, its a 4th gear.

On all the previous cars I've had with Overdrives (Sunbeam Rapier, Humber Sceptre Estate, Series III LandRover) the Overdrive is a separate gearbox that raises the ratio of the main box (only works on 3rd & 4th on the Chrysler cars as it needs oil pressure to work).

I guess there's no point in switching in and out of O/D when towing then as it doesn't give the lower gears an easier time.

it isn't a separate gearbox and it functions as a 4th gear but it is a separate fairly complex assembly within the gearbox, not just an extra cog, that gives an overdriven gear ratio, with 1-3rd handled by another separate fairly complex assembly. When OD/4th is engaged iirc drive still has to pass through the 1-3rd assembly but configured so none of those gears are engaged. afaik with custom programming you could engage another gear at the same time as OD but I don't think that wouldn't be very useful.

 

[uHu]

On the 4-sp box there is a point in switching the 4th (OD) off. The idea is to prevent overheating by letting the converter lock up. The 4-sp box will only lock the converter at the top gear (4th), but will lock in 3rd instead if you deselect 4th (OD Off). At full steam, and the converter converting (!), there will be several kilowatts of heat generated by the converter, so you're better off in 3rd locked than in 4th unlocked.

All this can be changed, of course, with a different valve assembly...

 

[BobMurphy]

I am an Autobox Virgin . . . And I have a headache .

I think I see what it does, but not how it does it (which is what I aspire to understand). I was switching in and out of O/D when towing a horse up and down hills the other day, it sounds as though I was doing the right thing after all.

I need to bone-up on how this box works .

OK - another couple of questions:

1. Does 'L' lock the box in 1st, and should one always use that when in Low Ratio on the Transfer Box ???

2. Does '2' start the car off in 2nd in order to reduce the torque at the wheels (i.e when on ice/snow) ??

3. If 2. is correct . . does it change up normally once its rolling or do I have to switch to 'D' when it's up to speed for 3rd ??

I have driven Autos in the past, but this is the first time I've owned one in 50 years of driving .

Bob.

 

[Chris]

1. Yes it does. It locks the whole thing in 1st only regardless of hi/lo box of course. No, no need to be in L when in lo. You can use the whole range.
2. Yes, 2 start effectively locks out first gear for slippy starts
3. Yes it does. Provided that you don't have the lever in 2 of course in which case you will be in 2nd forever.

Caveat warning.

Just remembered that I think the box has a self protection mechanism. If you lock it in 1st then rev the knackers off it like a drongo, it changes up into 2nd at some point just before the whole thing blows up.

 

[BobMurphy]

Thanks Chris .

Bob.

 

[uHu]

Just to clarify - as it sounds like you 2 are possibly misunderstanding each other.

The "2nd start" button makes it start in 2nd gear, the rest of the shifts are according to the position of the gear lever.

When you start with the gearshift in 2, (and the 2nd start not pressed) it still starts in first, and changes to 2nd as ususal, but not higher gears. If you change to 2nd from a higher gear (D (3 or 4)), it will not shift to 2nd unless the speed is low enough to allow 2nd gear. (And that's a good way to reduce the speed without using the brakes)

 

[BobMurphy]

Thanks Uhu,

So . . . .

'L' Limits the box to 1st gear (unless its about to explode).
'2' Limits the box to 1st & 2nd gear.
'2' With "2nd Start" button pressed limits the box to 2nd gear.
'D' With "O/D Off" limits the box to 1st, 2nd & 3rd gears.
'D' With "2nd Start" button pressed and "O/D Off" limits the box to 2nd & 3rd gears.
'D' With "2nd Start" button pressed and "O/D On" limits the box to 2nd, 3rd & 4th gears.
'D' With "O/D On" gives 1st, 2nd, 3rd & 4th gears.


Phew .

The next topic is likely to be "Torque Converters" as I can't believe its supposed to be this slow at getting moving .

Bob.

 

[uHu]

Sounds right.

It is very slow at getting moving. Takes up to one sec from pushing the pedal all the way until it reacts, depending on the conditions. Some of the delay is due to emmision values, it takes time to speed up quickly without polluting a bit extra.

The newer 5-speed HDJ100 is quicker, both because of a new combined ECU for the engine and the gearbox, which makes communication faster, and because of a different algorithm for controlling the IP. In addition there are a few mechanical changes.

There is a junction I go through every day, 90 degrees, onto the mainroad, where I used to push the pedal as I entered the junction with the 2000 4-speed (even on snow, as nothing would happen until I was through the curve and going straight again). When trying the same with the 2004, I had problems keeping my lane because it accelerated much faster.

 

[BobMurphy]

Thanks uHu,

It does get up to speed eventually, but I miss the immediacy of the manual '95' which I much prefer.

I'll stop worrying .

Bob.

 

[Brian the Sn@il]

I can confirm the 5 speed auto on a V8 is like shit off a shovel when pulling away.
Certainly not I was expecting when I test drove my old bus way back in 2013.
Throttle response from the fly by wire is instant

 

[Scott]

My FZJ105 has the '2nd Start' button, I found it very useful when climbing step mountainsides which had many shelves to creast. When in low range with 2nd gear selected the box would kick down to 1st as you back off over the creast, which then meant that the box generated a load more heat as it quickly went through 1st and changed up into 2nd to gain momentum to continue climbing. To eliminate the box kicking down into 1st and risking excessive heat build up, '2nd Start' was selected and did a great job of keeping the truck in 2nd and helping me manage the box temperatures (ambient temp was mid forties in an Australian summer).

The only part of an autobox that I haven't mastered yet is driving through the brakes when negotiating very steep descents in low range with a fully loaded truck. I reckon I'd just boil the brakes, but I'll play with it one day.

 

[Chris]

Ahh well the trick there is to pop it into neutral. In low there are times when the torque is so great it's pushing you against the brakes. Go to N and suddenly you stop dead! You may think you are sliding but you are not you are actually being driven. It allows for very precise control. No not all the time, when it's clear ahead just use what little engine braking there is.

 

[Scott]

Agreed, you can use that technique but in my opinion that is only suitable in situations where there is enough grip to hold the vehicle on the brakes preferably not at the top of a long descent. Going down a long steep mountainside descent in neutral wouldn't be wise, the vehicle wouldn't be under control, you need the vehicle in gear to provide what engine braking it can, but also so that if it all starts going wrong you can hit the throttle and accelerate, pulling the vehicle straight. If you weren't in gear then by the time you'd reacted you would most likely have rolled, some of the places I've driven a roll would be closer to being measured in minutes rather than seconds, with help a long way away.

Apologies for going slightly off topic. To recap, selecting neutral and controlling the vehicle on the brakes is one option under the right conditions, or driving though the brakes is another. Both come with experience and practice, but would only really be needed in tough off road driving.

I did select neutral once when in high range and driving on a very icy road, I was trying to slow the vehicle the last 5mph to a stop, but found that I keep losing traction and sliding, I soon realised that I was fighting to stop the vehicle against the engine driving me forward in D, as well as the momentum of the vehicle. Selecting neutral had an immediate improvement in the brakes responsiveness and the vehicle came to a stop. Worth remembering if we have another harsh winter.

 

[Doodle]

With the 100, low 1st gives a very slow and controlled descent with minimal push.