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The redesigned WJ
1999 Grand Cherokee shared just 127 parts with its predecessor. The structure was stiffened by Porsche
Engineering for sharper steering and lighter weight. The spare tire wasrelocated from the side of the cargo compartment to under the floor togreat relief of owners. The two heavy pushrod V8 engines
were replaced by chrysler's first clean sheet V8 since the 60's (SOHC
aluminium heads, plastic intake), Chrysler's then-new PowerTech
. Although this engine produced less torque
than both previous V8s, it was lighter and got much better fuel economyand provided similar on road performance figures (the 23 gallon fueltank was replaced with one of a 20.5 gallon capacity). The Inline 6engine was also updated in 1999. 10 horsepower (7.5 kW) was added byredesigning the intake manifold. The manual transmission
was dropped with this model.
While other Jeep vehicles used the Mopar 5 x 4.5 bolt circle, thiswas the first Jeep following the 1987 Chrysler buyout to receive awider bolt pattern — 5 x 5. The 5 x 5 bolt pattern (also 5 x 127 mm),although common to GM rear wheel drive vehicles and light dutytrucks/vans, has spread beyond its use with GM (and Ford
with their 1973 to 1978 LTDs
). Chrysler first used the 5 x 5 pattern on full-size half-ton Dodge Ram
pickups and Dodge Ramcharger
SUVs in 1986.
A notable feature available in this generation was the automatic four wheel drive option called Quadra-Drive II
.With three viscous clutches, it was one of only a few four wheel drivesystems at the time with triple locking differentals, joining thecontemporary Mercedes Gelandewagen, Mercedes Unimog and Magna SteyrPinzgauer, and the only one of the four with fully automatic operation,although the axle differentials could not be manually locked like inthe other three vehicles.
and 545RFE automatic transmission
in the WJ was notable. It included three planetary gear
sets rather than the two normally used in a four-speed automatic. Thisgave it six theoretical speeds, and it would have been the firstsix-speed transmission ever produced in volume, but it was programmedto only use five of these ratios. Four were used for upshifts, with adifferent second gear for downshifts. Although five of the six ratioswere used, Chrysler decided to call it a "4-speed automatic". In 2001,the programming was changed to make use of all six ratios. Rather thanhave six forward gears, the transmission was programmed to act as afive-speed with the alternate second gear for downshifts. The RPM at70 miles per hour (110 km/h) on a 545RFE is 2000 rpm, 200 rpm less thanthe 45RFE programming. 1999 and 2000 model year WJ owners can havetheir 45RFE transmission's programming flashed to enable the extra gearas both transmissions are physically the same. The 42RE 4-speedautomatic remained the transmission for the Inline 6 engine. It was notchanged from the previous model Grand Cherokee's.