I

21 DECEMBER 1967 Yot t27 No. 374e

Editor Doputy Editor Asisteni Edltor Foaturar Editor

Sport. Editot

A6sistant Tochnicol Edltor

Editorial

Midlrnd Edhor

Art Editor AsiBtant

Mrnchest.r Olfico

Sp6clal ContributoB

M.naglng Olrector

MAURICE A. SMITH, OfC PETER GARI{IEF LEONARO AYTON STUANT BI4DOil INNES IEELAND GEOFFREY HOWARD,

ESctEng), ACGI, GlMechE

JOHN DAVEY GRAHAM SOBSON, MA(Oxon) MARTIN LEwlS MICHAEL SCARLETT WARREN ALLPORT

EDWARD EVE6

HOWARO VYSE JOHN HAWKINS

HAROLD HOLT, AMIML AMAET

RONALD BABKER ROGEF HUNTING"T ON, ASA E ( D etrcit) EOIN YOUNG {Spon}

MAI]T FEATURES TEST COCKTAIL: OPUS-HRF

2.LITRE TRANSIT ESTATE LOTUS.FORMULA.FORD

THE M]SJUDGED MATCHMAKER TEST: M0RRIS 13OO LOOK OUT! M1 EXTENSION DESIGN ANAIYSED: ALFA GIULIA GTV COBGI'S MINIATURE MOTOR INDUSTRY OtD POSTERS TRIUMPH DOLOMITE STRAIGHT.S

Page

2 4 6 8 14 19 20 22 26 2A 33

REGUIAR ITEMS DISCONNECTED JOTTINGS NEW PRODUCTS THE SPORT PICWEEK NEWS AND VIEWS TRADE AND INDUSTRY STRAIGHT FROM THE GRID CORRESPONDENCE NEW CAR PRTCES Last pages beforc back cov6r

17 30 38 42 4it 45 46 47

COVER: Opus Ford and Lotus-Ford. Photography: Michael Cooper

NEXT WEEK'S ISSUE FEATURES-P.49

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TOWING WITH AUTOMATIC TRANSMISSIONS

MANY motorists have. been alarmed, in some cases quite unnecessarily, by a recent warning from the Automobile Association about towing caravans or heavy trailers behind cars with automatic transmissions. There have, apparently, been cases of overheating, where the transmission has been damaged. The technical facts are as follows.

All automatic transmissions contain a fluid device in which oil is churhed during take-up from rest to provide a "slipping clutch". ln a box employing a hydraulic torque_ convertor (Borg-Warner, Powerglide, Automotive products- BMC. and ZF) this churning effect is used, up to quite high revolutions, for multiplication of the tractive effort. lnevi- tably, this process causes the oil to heat-up, and a separate cooler is fitted to many installations to keep the tempera- ture down under extreme conditions; indeed, the torque- convertor itself acts as a cooler, since it is finned for this purpose, and the gearbox sump capacity is in any case much larger than that of a manual box (in the order of 12 pints) to give a good circulation and a "heat sink".

There will be a danger of overheating only if certain basic rules are ignored, and most experienced caravanners will already be familiar with them. First, the weight of the caravan should not exceed three-quarters of the weight of the car; 1O cwt of caravan per litre of engine capacity is a good rule to remember when choosing an outfit.

Struggling up a gradient in slow-moving traffic, a driver may be reluctant to kick-down, since this will accelerate him towards the vehicle ahead. Thus, he labours on, with the torque-convertor churning and the temperature rising progressively. Adding to his troubles is the fact that the engine too is overheating, and some of this heat is transferred back, raising the ambient temperature in which the transmission is working. lt is in prolonged conditions such as these that damage can occur, and drivers should always use the "lock-up" to change down into a lower gear-just as they would with a manual gearbox.

On cars already fitted with a transmission oil cooler there is much less danger of overheating; where there is no cooler one can be fitted (and this is advisable if hard towing use is anticipated) at an extra cost of between C2O and e3O. lt is much better if this is mounted in front of the main water radiator, rather than in some shrouded area. Cars fitted with coolers as standard are all Jaguars, Vanden plas Princess ' R, Rover, Aston Martin, Simca 1SOO, and Maserati. ln fact, all Borg-Warner Model 8 transmissions have one as standard.

As with an ordinary manual gearbox, inconsiderate use will cause damage. When towing it is important to remember that the system is being subjected to more stress than normal-so try to develop a mechanical "sympathy" for the components you are stressing.