Diffs and ranges

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Sorry to post this twice under diffierent headings.
Say, I am driving along in high range and come across something unexpected, can I simply engage the diff if I have to, asuming I don't want to stop. Similarly can I shift from Hi to Lo range without stopping. Is it best to stop, essential to stop or does it not matter with respect to shifts in ranges and engaging diffs?
Regards Tony
 
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On 6/5/05, Tony Steele <[Email address removed]> wrote:
d,
Tony
The manual does not give specific recommendartions for engaging CDL
while in High, and the CDL is switched on automatically when the
transmission is shifted to Low.
Changing from High to Low: manual - max speed 5 mph, auto - stationary
Engaging CDL
--
Rgds,
Roman (London, UK)
'92 HDJ80
 
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Tony

I've found that you can engage the centre diff-lock on the move (I'm assuming you've installed the dash button) so long as your speed is "slow", which I would translate as 5 - 10 mph or less. I've done this many times when it starts to wallow a bit in mud, and in fact if I see a particularly boggy bit coming up I tend to pre-select front and rear diff-locks too and use the dash CDL switch to flip all lockers on/off.

However I think the important words in the paragraph above are "slow" and "in mud". Taken together these mean that there are no nasty shock loads on the transmission when the diff-locks engage. The one thing I would never do is engage any diff-lock while I had significant wheelspin, since the inertia loads from suddenly bringing the spinning wheel(s) to a halt could do some nasty damage.


I have a manual box, and I've tried shifting from hi to lo and back again on the move, and have found that it invariably results in nasty grinding noises unless

either: I am completely stationary (and obviously I've dipped the clutch)
or: I am only moving VERY slowly, AND the main gearbox is in neutral, AND I've dipped the clutch

As Roman says the user manual states that with a manual gearbox you can change from high to low at < 5mph, but I've tried this and it really doesn't like it unless you meet the "or" criteria above (and then trying to juggle two gear-levers and clutch before you come to a halt makes it a waste of time).

I use low range quite a bit when hauling the horses around, as it allows really slow movement on bumpy surfaces. 3rd/low seems about the same as 1st/high; and 5th/low slightly lower than 3rd/high, giving a top speed of about 50mph. So if I see a mixture of OK-ish and bumpy ground coming up I tend to select low range anyway since it doesn't really compromise off-tarmac top speed. The transmission whirrs a bit at higher speeds though! I sometimes use low range in town too if I have a heavy trailer and there is going to be a lot of hilly stop/start driving, but this wouldn't be necessary with an auto box.

Christopher Bell
Devon, UK
1996 1HD-FT
Say, I am driving along in high range and come across something unexpected, can I simply engage the diff if I have to, asuming I don't want to stop. Similarly can I shift from Hi to Lo range without stopping. Is it best to stop, essential to stop or does it not matter with respect to shifts in ranges and engaging diffs?

Regards Tony
 
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Guest

Guest
This has already been stated I think but my advice would be to be gentle to
your transmission as over rough and difficult terrain it is going to be
working hard for you anyway. In my experience it is always best to stop, put
the car in N ( I have an auto) and then change ratios and/or switch on the
lockers from there. If you are about to go into difficult ground it helps
focus the old brain a bit too.
You must be heading off soon if I remember rightly...?
Jeremy
On 5/6/05 23:58, "Tony Steele" <[Email address removed]> wrote:
> Sorry to post this twice under diffierent headings.
>
> Say, I am driving along in high range and come across something unexpected,
> can I simply engage the diff if I have to, asuming I don't want to stop.
> Similarly can I shift from Hi to Lo range without stopping. Is it best to
> stop, essential to stop or does it not matter with respect to shifts in ranges
> and engaging diffs?
>
> Regards Tony
>
Jeremy Llewellyn-Jones
 
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Morning Christopher
The only time SO FAR hope to chage all that in a while unless it blows up or breaks down etc. But The only time the centre diff on mine had been engaged is when im cleaning the dash and I accidently press the switch and its only when I go to drive away later that I know what I did.
If you are stopped and engage the low range and then put the centre diff on and then put the front and rear diffs on at what speed can you then put it into high and what will this do.
What happens if you only engage the centre diff, the rear front diffs on their own.
In what order do you engage all these, and do you need to engage some or all of them.
If these have not been used for yonks could they stick or not work, or work and then stick and you could be left needing the Toyota man and a tow. I know but I had to ask knowing my luck with the cruiser. Thanks
John C
92HDJ 80 1HDT Ireland
 
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On 6/6/05, Jeremy Llewellyn-Jones <[Email address removed]> wrote:
e
Jeremy
AFAIK, with the auto box, you can move the H-N-L lever only when the
auto box is in P or N. In all other postions it is locked.
--
Rgds,
Roman (London, UK)
'92 HDJ80
 
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In both my posts on this I have said I put the car in N...
On 6/6/05 10:38, "Roman" <[Email address removed]> wrote:
Jeremy Llewellyn-Jones
--
 
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On 6/6/05, Christopher Bell <[Email address removed]> wrote:
HelloChristopher,
n't
e
You can have some succes with smoother changes by practising the
double-declutching technique, like they used to do with the old style,
non-synchro gearboxes, but the shock load can't be avoided .
Changing from low to high on the fly is possible and, with practice,
can be done at any speed. The trick is not to overshoot by going
straight from low to high before declutching in neutral.

I
and
be
So far I've not found a use for the low range, the bl00dy thing will
go anywhere in high, even with a two tonne trailer at the back up a 30
deg. incline. And in low range it will climb a steep hill on tarmac at
idle speed.
--
Rgds,
Roman (London, UK)
'92 HDJ80
 
G

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Guest
Great information, thanks.
I am now going to try the diffs and ranges. I just did not know what to do
with them before now; its the sort of thing that is in a manual I guess.
I expect in an hour or so I will have a whole new set of questions and be
able to say whether the things still work after not being used for a year.
Regards Tony
 
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John

The only time SO FAR hope to chage all that in a while unless it blows up or breaks down etc. But The only time the centre diff on mine had been engaged is when im cleaning the dash and I accidently press the switch and its only when I go to drive away later that I know what I did.
You should see a very obvious orange light on the dash when the CDL is engaged, and the ABS light (if you have ABS) will also come on, as this is disengaged when the CDL is on.

If you are stopped and engage the low range and then put the centre diff on and then put the front and rear diffs on at what speed can you then put it into high and what will this do.

You can put it into high range at any speed - from the mechanical point of view the diff-locks and the hi/lo transfer mechanism are independent. There is no clever interlock that disengages them above some certain speed.

However you will find that driving at in anything other than a straight line with the diff-locks engaged gets a bit hairy since they will act to stop you turning, and this becomes downright dangerous very quickly if you build up any significant speed.


To demonstrate this the best thing I can suggest is to find a large, flat slippery area such as damp field (with no obstacles) and try it. It should be slippery enough to permit the wheels to skid so that you don't put too much strain on the diff-locks - ie DON'T try this on tarmac.
Firstly engage just the centre diff-lock. You'll find that it doesn't make a lot of difference except that you will get a bit of understeer on tight turns as you will generate some wheelslip. (This is because the rear axle will want to turn a tighter radius than the front one, so travel less far, but the centre diff-lock won't permit this. On grass if you look behind you you will see slight skid marks where the wheels have slipped a bit to permit the turn.)

Now engage the rear diff-lock (you may have to zig-zag a bit to get this to engage). Immediately you will find that the truck is far more reluctant to turn. (This is because in any turn the two rear wheels want to travel at different speeds, but the rear diff-lock won't permit this.)

Finally engage the front diff-lock too (again, you may have to zig-zag a bit). Now you will find the steering gets heavier, and that turning becomes really difficult as all four wheels want to travel at different speeds but instead they are all rotating at the same rate. On a really muddy surface you may find yourself squidging along in a straight line despite having the front wheels on hard left or right lock.

(In fact I find the rear and front diff-locks positively unhelpful sometimes when manoeuvering on mud as I simply have no steering at all. Try doing a three point turn with all diff-locks engaged, and you'll see what I mean.)

The point I'm trying to make is that the differentials are there to permit the wheels to travel at different speeds in normal use, and this is how 4 wheeled vehicles negotiate corners. Locking them up might give you more traction by reducing wheelspin, but this will be at the expense of handling to the point of making the vehicle almost unsteerable.

Unsteerable + any significant speed =3D accident, which is why the standard Toyota setup only permits diff-locks to be engaged in low range since, by implication, you will almost certainly be travelling slowly. By fitting the dash override switch you can engage them in high range too, and so long as you go slowly there is nothing inherently dangerous about this.

What happens if you only engage the centre diff, the rear front diffs on their own.
Well I hope I've explained it above - the only real answer is to try it. And in fact you can't engage either the front or the rear locks on their own - the centre lock has to be engaged first as there is an electrical interlock from this to the front & rear.

In what order do you engage all these, and do you need to engage some or all of them.

Toyota have engineered it so that they should only engage in the order centre, rear, front; and if you try the damp field idea above you will easily see why as this order progressively reduces the driveability of the truck.

They have built in some interlocks, so that the front and rear locks can only engaged if the centre has actually locked up (and if it is unlocked then they will automatically disengage). Also the front and rear switch rotates through "rear only" to "front and rear", so you have to select rear before front.

Note that I use the word "select" when talking about front and rear. Because the cogs have to line up internally they won't necessarily engage, despite being selected, until this happens (this is why I say above that you may have to zig-zag a bit). So if you select both front and rear you may find that the front engages before the rear, as those cogs line up first. The red lights on the dash flash when they are "selected" and go steady when they are "engaged".
If these have not been used for yonks could they stick or not work, or work and then stick and you could be left needing the Toyota man and a tow. I know but I had to ask knowing my luck with the cruiser.
As for working and/or sticking. Well the rear in particular is notorious for gumming up and then not engaging, or being slow to engage. From what I've read over the years on these forums if previous owners have done much deep wading, getting water into the mechanisms, and they haven't been used for some time, the actuator mechanisms may gum up. It seems to be accepted wisdom that all the actuators should be "exercised" from time to time.

In the same way that the cogs have to line up to engage they also have to line up, thus releasing the pressure on them, to disengage. On my truck the centre almost always disengages immediately, then the front, then lastly the rear.

Therefore disengagement is usually harder than engagement since, in real life, you tend to engage on a slippery surface because you are getting wheelspin - making it easier for the cogs to line up. However you disengage when you are back on firmer stuff, where wheelspin is less likely. I have found that zig-zagging, particularly alternating between forward & reverse, is the best way to take the load off the transmission and hence to let the locks disengage.

Could they lock on? Well possibly I suppose. But I think this is very unlikely - if the actuators can engage them the mechanism should be OK to disengage too. If they do lock on I suppose the best bet is to jack up one side of that axle, and spin the wheel manually to its central free position where you will be able to feel the absence of load on the transmission. I honestly don't think you need worry about this.


I hope this helps. I'm not a serious off-roader: like you I simply use my truck to go where I need to go, and my experience is limited to muddy fields. But you can learn a lot - at no danger to either yourself or your truck - in a flat muddy field!

Christopher Bell
 
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Roman
|
| You can have some succes with smoother changes by practising the
| double-declutching technique, like they used to do with the old style,
| non-synchro gearboxes, but the shock load can't be avoided .
|
| Changing from low to high on the fly is possible and, with practice,
| can be done at any speed. The trick is not to overshoot by going
| straight from low to high before declutching in neutral.
Yes, I'm familiar with double de-clutching (my old VW Beetle got seriously short of syncromesh in its old age). However I normally have a horse on the back when I need to shift between high and low, and the last thing I want is to jerk it about due to inept gear changes!
|
| So far I've not found a use for the low range, the bl00dy thing will
| go anywhere in high, even with a two tonne trailer at the back up a 30
| deg. incline. And in low range it will climb a steep hill on tarmac at
| idle speed.
I think this is a characteristic of the auto box: the torque multiplication at low engine speeds makes low range almost unnecessary. I mainly use low range it to get low road speed, as Julian will tell you our drive bears an uncanny resemblance to a tank training ground, and I like to tow the poor nags up it slowly. But there's no way I could hill-start the 3 horse box on the 1-in-7 hill in our village in high range without murdering the clutch.
I think the manual transmission in these beasts is less satisfactory in many ways from a driving point of view, except for 'ornery sods like me who like to be in charge - and of course from the point of view of fuel consumption.
Christopher Bell
 
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Chris wrote
"As for working and/or sticking. Well the rear in particular is notorious for gumming up and then not engaging, or being slow to engage. From what I've read over the years on these forums if previous owners have done much deep wading, getting water into the mechanisms, and they haven't been used for some time, the actuator mechanisms may gum up. It seems to be accepted wisdom that all the actuators should be "exercised" from time to time."
I think I may have this problem of the rear and front diffs not locking. I remember when I first bought mine a year ago I fiddled about a bit and saw speperate red "icons" appearing on the dash display for the rear diff locked and maybe, although I am less sure about this, for the front and rear locked. Now I only get the central diff "icon" appearing and turning the dial to rear and to rear and front does not seem to make any difference.
I am planning a long W Africa and Sahara trip; should I get the rear and front diffs fixed or try to manage without them. Are they difficult to fix? Is it likely that they are working but that the indicator "icon" is just not working?
Many thanks
Tony
 
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Tony

Roman is the expert, but this may help:

Turn the ignition on, but don't start the engine. Engage centre diff lock. You should hear a "whirr ... click" noise from underneath the gearbox and, if all is well, the centre diff locked orange light will come on. (If it doesn't come on you may need to roll the truck fowards a bit on a gentle curve until it engages.) You appear to be getting to this stage successfully.

Now turn the front/rear diff-lock switch one click to "rear only". You should hear "whirr ... clonk" from the rear diff, and the red diff lock light should flash (it's very unlikely to engage, and hence give a steady red light, while stationary unless you happen by chance to have halted with the cogs aligned.)

(1) If nothing happens - no "whirr", no dash light, no noise, no nothing - then the problem is probably electrical. Either the ECU is on strike, some wiring has been pulled out under the dash or underneath the body, a fuse has blown, or some other such gremlin has crept in.

(2) If you get a "whirr", but no red light, then this suggests that the rear diff-lock actuator and wiring are OK and it is simply that the bulb in the dash is blown. You still need to test that the diff-lock engages fully, and you'll need to have the vehicle moving to determine that.

(3) If you get a red flashing light, but no noise from the rear, then the dash bulb and ECU are OK, but the actuator is probably gummed up solid.


Now try moving the switch another click to "front and rear", and go through the same process: this time any noises should come from the front diff. In all cases the noises should be very obvious with the engine off, and clearly audible even with the doors and windows shut.


If the answer above was (1) then you are going to need to do some electrical diagnosis. Check the obvious things first: ie diff-lock fuses and any wires yanked out of sockets underneath. If those check out I'm afraid you'll need the field service manual (which I don't have, but others do) and a multimeter. Let's cross that bridge if we come to it.

If it was (2) then you are probably OK. Try driving on a slippery surface and engaging the diff-locks - if they are working it will be very obvious from the change in handling (see my comments to John O'B on this). You may want to replace the bulbs in the dash (see Roman's guide to getting it apart). If they refuse to engage, despite whirring noises, the actuators are probably gummed up but repairable if dismantled and cleaned.

If it was (3) then conventional wisdom seems to be to take the actuator apart. Some report that cleaning up and greasing it restores it to health and efficiency, others have found theirs rusted up beyond repair and have had to get a new one from Toyota. I don't know how hard it is to dismantle, but again lots of advice will be available.


But be hopeful: if it worked a year ago then it may be a touch arthritic, but there is no real reason why it shouldn't work now. I recall a post from someone in Colorado who said that after a week of being switched on/off repeatedly due to driving in snow his front & rear locks, which previously had been reluctant to engage, now worked beautifully.


Will you need it in the Sahara? I don't know - muddy fields in Devon are my habitat. In my experience the front and rear diff-locks are useful right at the margin of traction, when maybe you've got just one wheel on good terrain and they can make the difference between crawling out and looking stupid. I'd certainly want mine to work if I were going there.

On the other hand lots of Landrovers make it across Africa, and they don't have cross-axle diff locks. I should think the right tyres, a winch and a good off-road training course are probably much more important.

Christopher Bell

ps: I seem to remember reading somewhere that using the front diff-lock when going downhill was a BAD THING, because you might not have any steering ... take a look at http//www.mattsavage.co.uk/rollover/rollover.mov <http://www.mattsavage.co.uk/rollover/rollover.mov>

I think I may have this problem of the rear and front diffs not locking. I remember when I first bought mine a year ago I fiddled about a bit and saw speperate red "icons" appearing on the dash display for the rear diff locked and maybe, although I am less sure about this, for the front and rear locked. Now I only get the central diff "icon" appearing and turning the dial to rear and to rear and front does not seem to make any difference.

I am planning a long W Africa and Sahara trip; should I get the rear and front diffs fixed or try to manage without them. Are they difficult to fix? Is it likely that they are working but that the indicator "icon" is just not working?

Many thanks

Tony
 
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On 6/6/05, Tony Steele <[Email address removed]> wrote:
Tony
I bet you're familiar with this:
http://www.sleeoffroad.com/technical/tz_diff_lock_actuator.htm
As for fixing the car before a trip to the Sahara - it helps. Most
people who drive there make it across the desert, some don't. If you
join the latter group, you will be faced with a choice of paying
someone to get your car towed from the middle of nowhere to a repair
shop or being towed by the friends you travel with. The first option
may cost you your nest year's holiday. The second may cost you many
hours, or even days, of driving eight meters behind another car,
without the engine running, so no A/C,, no PS, no brakes, staring
intensly in the brake lights of the car in front, being jerked each
time the tow rope pulls tight. It will also cost you the respect of
your friends when they learn you new about the problems but never
fixed them.
Sorry if it sound a bit harsh but I've been with people who went on a
trip just hoping they would get by with a little help from the others,
in cars with broken diffs, no oil in the transfer box, leaking fuel
tanks, dodgy engines. The other guys can't say "OK, it's not my car,
so it's not my problem", they just have to tow the old bugger for
hundreds of miles across the most inhospitable part of the world.
--
Rgds,
Roman (London, UK)
'92 HDJ80
 
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Guest
Hi Roman
Thank you for the URL.
I think it is most likely that the problem I have will be with the diff dial
on the dash because some light switches fitted just below the dial. Atleast
that is where I think I will start looking. I suppose this could be tested
by seeing if there was a switching voltage being transmitted to the
actautors, wherever they might be.
If I get to the stage of needing to look at the actuator do you know anyone
near Bristol who could look at them?
Incidentally, it is definately not the indicator light that is not working
because for a brief second or so these light up when the ignition is turned
on.
Regards Tony
----- Original Message -----
From: "Roman" <[Email address removed]>
To: <[Email address removed]>
Sent: Monday, June 06, 2005 7:29 PM
Subject: Re: [ELCO] Diffs and ranges
On 6/6/05, Tony Steele <[Email address removed]> wrote:
Tony
I bet you're familiar with this:
http://www.sleeoffroad.com/technical/tz_diff_lock_actuator.htm
As for fixing the car before a trip to the Sahara - it helps. Most
people who drive there make it across the desert, some don't. If you
join the latter group, you will be faced with a choice of paying
someone to get your car towed from the middle of nowhere to a repair
shop or being towed by the friends you travel with. The first option
may cost you your nest year's holiday. The second may cost you many
hours, or even days, of driving eight meters behind another car,
without the engine running, so no A/C,, no PS, no brakes, staring
intensly in the brake lights of the car in front, being jerked each
time the tow rope pulls tight. It will also cost you the respect of
your friends when they learn you new about the problems but never
fixed them.
Sorry if it sound a bit harsh but I've been with people who went on a
trip just hoping they would get by with a little help from the others,
in cars with broken diffs, no oil in the transfer box, leaking fuel
tanks, dodgy engines. The other guys can't say "OK, it's not my car,
so it's not my problem", they just have to tow the old bugger for
hundreds of miles across the most inhospitable part of the world.
--
Rgds,
Roman (London, UK)
'92 HDJ80
 
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Christopher
Thank you for detailed trouble shooting guide re diffs sent yesterdy; very helpful and I will follow it through and see what I can find out.
Tony
 
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Hi all
My 94 1HD-T until recently the back diff keep on flashing but the diff actually locked, the front one didn't blink and also locked. I'm sure they all locked fine because I tested in the mechanic with all wheels in the air and they sure locked fine.
A week or two ago when I installed the walbro (soon I'll report on the walbro) the electrician finally found the problem: It was the return signal wire that was sectioned. Now all things work as they should and I'm intending to install the central diff lock switch.
What puzzles me is: Before the repair if there was no return signal from the rear diff as being locked how come the front diff locked anyway, does anyone knows if the diff ECU as some kind off fail safe operation, that after some time if the central diff is locked the front will also lock anyway regardless off the rear diff state.
Now I also experience that the rear diff as the slower one to engage or disengage the central and front ones, comparably, lock very fast. I'll try to exercise them at least once a week :)
Regards
Joaquim
94 1HD-T Portugal
-----------------------------------
Chegou o Clix Turbo ADSL a 16 Megas
Internet + Telefone sem assinatura telef?nica
Saiba mais em http://adsl.clix.pt
 
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Joaquim
| What puzzles me is: Before the repair if there was no return
| signal from the rear diff as being locked how come the front
| diff locked anyway, does anyone knows if the diff ECU as some
| kind off fail safe operation, that after some time if the
| central diff is locked the front will also lock anyway
| regardless off the rear diff state.
This is normal: I don't think there is any interlock between rear and front, it is simply that the switch has to turn through "rear" to get to "front & rear". My front usually engages long before my rear does.
|
| Now I also experience that the rear diff as the slower one to
| engage or disengage the central and front ones, comparably,
| lock very fast. I'll try to exercise them at least once a week :)|
My rear is slower too.
But on really slippery mud ALL my diff locks engage almost immediately, as the wheelspin permits the gears to line up quickly.
Christopher Bell
Devon, UK
1996 1HD-FT
 
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Roman
| ... The second may cost you many hours, or even days, of driving eight meters behind another car,
| without the engine running, so no A/C,, no PS, no brakes, staring intensly in the brake lights of
| the car in front, being jerked each time the tow rope pulls tight....
What a wonderful description of being towed! Is this the genesis of a new school of overland poetry?
Or is it perhaps an allegory referring to European Union membership "being jerked along sans brakes, sans steering, sans everything" (with apologies to WS).
Christopher Bell
 
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Hi Christopher
>This is normal: I don't think there is any interlock between rear and front, it is simply that the >switch has to turn through "rear" to get to "front & rear". My front usually engages long before >my rear does.
I had the impression that the dif ECU controlled the lock order but you are probably right since the front did lock.
In that case what's the ECU for (the black plastic box near AC the evaporator)?
I thought the diff ECU function was avoiding the lock above 5 km/h speed and control the engagement order. Now I don't know anymore. One of my deepest convictions is gone. Christopher see what you've done ;-)
>But on really slippery mud ALL my diff locks engage almost immediately, as the wheelspin permits >the gears to line up quickly.
That also hapens when the four wheels are on the air at the mechanic. And I also noticed the slippery the surface the fastest they seem to engage (a good thing).
Regards
Joaquim 94 1HD-T Portugal
-----------------------------------
Chegou o Clix Turbo ADSL a 16 Megas
Internet + Telefone sem assinatura telef?nica
Saiba mais em http://adsl.clix.pt
 
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