Re: Manual or automatic gearbox

I've spent some time now, looking for the right Jimny. But can't decide whether to go for auto or manual transmission.

I've read a thread here on bigjimny where the only real downside on the automatic is that it needs a cooler for transmission oil, as it gets hot.

But is it weaker than the manual gearbox? Or can it take the same beating in rough terrain?

And what about the automatic ECU and driving submerged? Can it be made waterproof?

Tom

The auto boxes are stronger than the manuals - and in addition, driving off road they provide smoother power transmission and tend to cause less stress to other components. They have no equivalent to 'first low, floor it and drop the clutch' - which is often a good way to bust stuff.

I would never go back to manual now.

The ECU is very simple (as ECU's go) and well waterproofed. It would be a simple matter to remote it to the headlining if you were concerned.

One of the biggest advantages IMHO with the electronic auto box is that you can 'persuade' it to lock the torque converter (there is a solenoid valve just for this). This is particularly useful if you want engine braking for hill descents and the like. You can also interface to the other solenoid valves (which operate the brake bands which in turn select the gears) to turn it in to a pseudo manual box where you can pick the gear you want rather than letting the ECU decide. A bit like a sequential shift on modern cars.

I hunted for 2 years to find a decent auto - and failed! Instead I've put in a Vitara, non electronic one in - but I'd much rather have the electroinic one!

Si

I've got a Jimny with an auto box (& rocklobster transfer box) and its great off road. When I bought the car it had about 35,000 miles on the clock and I would imagine the auto box had never had an oil change. The oil was quite dirty - brownish - which is not a good sign for an auto and suggests it had got hot at some time. I changed the oil and filter, and put a Mocal oil cooler on it and it has stayed clean over a few thousand miles. I plumbed the oil cooler in so that the oil went through the cooler first, and then through the cooler in the bottom of the rad. The reason for this is its possible to overcool the oil (in winter particularly) which the box doesn't like. The effect of this is that it won't change into overdrive 4th gear until its warm enough.
Its certainly easy to drive off road and with the low ratio transfer box engine breaking is ok. I use this car in the UK.
In France I also have a Jimny but bought a manual as I was concerned about the auto box overheating on some of the long steep rocky hill climbs we do. They are very hard on the car and as I understand the Jimny box was originally designed for a smaller engine (!) and is therefore working hard off road. I thought that the use I had for it might be too much.
So not wanting to confuse you - I like the the auto for UK use and of course its good to drive on the road too, but I'm not sure how durable it would be in a hot climate working hard off road. We are in the south and see temperatures approaching 40 mid summer.

Interesting Obarno. Looking into why my auto sticks in 3rd until well warmed up. About to have the g'box oil changed as I have read that might do the trick, but also understand there may be a sensor that might need kicking!

Thoughts? Is it a common problem? Is there a simple solution (is changing the oil the standard fix?)

Cheers

Its a common thing with these boxes - I don't think its necessarily anything wrong, unless of course a sensor is faulty, its the way they are. Changing the oil in mine made no difference. On a cold morning I can drive for a mile and half before it changes, on a warm morning maybe 1/2 to 3/4 of a mile. I talked to Rhino Ray - Ray Edwards - and he has the same experience with his auto trialler. So probably not anything to be concerned about.
As is said - that's why I plumbed the oil cooler for the oil to go through the extra cooler first, and then warmed if necessary by the radiator. I hope that this way it keeps the oil at the optimum temperature for the box.

Edit

To follow on from the above about temperature, I also have a 4ltr Wrangler auto here in France which I requently use off road. I fitted a temperature gauge to the auto box, which also has a large separate oil cooler, and found that the box gets hot if I use high where really I should be using low, and also on long climbs on the road. We went to the Pyrenees with it and there are some extremely long climbs on the back roads which made the box hot. Normal running is around 80 deg C but hot is around 120. Not good long term for the box so plenty of oil changes are necessary if the oil smells burnt.
Off road though, as Simon says, an auto is good to drive as you can creep over difficult bits and have the advantage of the torque converter for a useful bit of slip.

If it's a pre-electronic box - change the oil and filter. If you cannot source a new filter, you can wash out most of the dirt with petrol.

If it's an electronic box, it's probably one of the solenoid valves sticking. doing the above should help eventually (it's probably got dirt or overheated oil residue gumming it up). It might be worth flushing it through with something - if such a something exists! But with new oil, it may well fix itself.

Most Auto Boxes are susceptible to over heating and may not be helped by sticking an additional cooler in series. The reason is that they need high oil flow through the cooler. If you slow the oil down by increasing the resistance to flow, it has more time to overheat inside the box and may do the opposite of what you hope! This is particularly true of ZF Four speed Land Rover boxes.

If you are fitting a Mocal or similar cooler, go for one with a big bore / port size to offer the max flow possible. Then add a fan if you need to increase the cooling. Switch the fan with an in line thermostat. Motorcycle fans are good for this. They are tiny (15 cm diameter) and shift a huge amount of air.

My in line stat is set to 88C and off road, it runs the fan continuously with a 8" Square, 1" thick Mocal cooler. I would read into this that it needs quite a lot of cooling!

Si