Caravan World itemJan 2016

[Dunnit]

Refer Item Caravan World regarding towing a caravan. With 200series V8

Suggests towing in 4th gear and not in drive (D) to preserve the auto gearbox and probably better fuel consumption.

it indicated towing in D causes slipping in the auto box increasing heat to 120C from the normal 80-90C

Is there any substance in this report?

Caravan World mag Jan2016.pdf

[Woodduck5]

Hi Dunnit,

Most of the Cvan World article is pretty close to the mark.

Firstly, it is talking about a Petrol LC which has a 5 speed box.  The diesel has 6 and which (inho) should be towing in 5th.  But essentially the argument is right - the transmission slips (guarantee it will happen in top gear, when towing).  There was (is) a software update (certainly for the 6 speed box - not sure about the 5 speed) which changed the gear ratios slightly (only when used in S mode).  This allows the torque converter to lock up much earlier, primarily in 6th gear, but it effected all gears.  This means the stated 120Km/Hr is (maybe) a bit out of date.

I've tried exactly as outlined in the article, with a heavier van (22' 6" - 3 Ton) and I have a scan gauge.  I didn't get anywhere near 120degrees - and would have been quite concerned if it did.  It certainly did get much warmer than the normal 85 degree normal op temp, but not 120. 

Lastly - the statement about the torque converter locking up at a certain speed is technically incorrect.  It is more about the load on the gear box and the amount of torque that is being asked of it, to transfer from front (motor) to diff (wheels).  If you put your foot down to go up a hill and you are already doing 80Km/Hr in 4th - the Torque converter has two options (depending upon a whole stack of factors - but again, mainly on what torque is being asked to transfer) - shift down a gear - or slip.  It will (nearly always) slip first.  The revs will go up by around 400-500.  If the torque transfer wasn't enough to meet your foot pressure, it will drop back a gear.  This is exactly what is supposed to happen - it is designed that way.  So, the auto box is designed to compensate for this increased activity and therefore compensate for the temperature increase.

For those that may be fanatical - there is a mod that (arguably) makes the auto box work much more efficiently.  Reduces dramatically the torque slippage (like 90% reduction).  But it is not toyota approved, is guaranteed to void warranty and about $3K.  But it does (reportedly) improve fuel consumption (when towing) but 30%.  It is used by (the likes of) Dakar racers and the like.  I have only seen it used/advertised overseas.  I doubt if it is for anyone on this forum.

Bottom line - yes, tow in (one down) from D in the LC200.  You will get better response, the car will like you more (less stress on just about everything), and better fuel economy.

Regards

[Dunnit]

Thanks Woodduck5 the article did not mention diesel? and mine is a V8 GXL diesel! Your comments are well received Thanks.

[Wazz]

Just to confirm - S5 for towing vans with a diesel LC200?

Edited February 9, 2016 by Wazz

[Woodduck5]

Warren

Yes - S5 in a Diesel LC200.

Both the car and the fuel economy will like you for it.

Regards

[Wazz]

Thanks Geoff.