NissanDiesel Forums

Hey i have a Nissan Laurel (rd28) 1990, and the torque converter is not locking up, any ideas of whats going on and how to fix it.. how much will it improve my full economy if i get it sorted?

Thanks Daniel

It might take a while to get really specific answers on this. The RD28 engine was never offered in the U.S. Somebody from your section of the globe will speak up sooner or latter. Our closest parallel would be the LD28 in the Maxima. I think the lockup will help 1 or 2 MPG in that application, but to tell you the truth, I don't have much factual basis for that answer.

Dave (AU) will pipe up later tonight, I'm sure. He knows RD28s.

C32 is listed as a 90 model in europe its fitted with a L4N71B.
its similar to the LD28 auto fitted to the USA maxima.2 vesions of this transmission.both are listed in service manuals.
L4N71B has a hydrolic/mechanical operated lockup.when governor pressure equals line pressure[70-80KM-H] and is in 4th gear it dumps oil pressure from the lock up cancel circuit.

EL4N71B has electric lock up cancel solinoid.when in 4th gear the solinoid needs to be earth switched to get lock up.some will lock up in any gear but these are rare.

WARNING most L4N71B have electric cancel setup but dont have the internal gear selection switches.these dont have a power shift setup of a full EL4N71B BUT MAY HAVE A POWER SHIFT SWITCH AND LIGHT.mine has a overdrive cancel light but power shift switch.these are more common and are used on most nissans of the mid/late 80's.if you unplug the solinoid/loose ignition power/trans controler earth it will not lock up.the wiring gets damaged or burnt as its near the exhauste.

C33 is fitted with a full electronic auto. 1989-93 JDM models.
RE4R01A [ on blue id plate].i think these are good as scrap.
they work well or they dont.they need all other systems in the car to work to get a correct shift.they could also not lock up if the touque convertor is worn out.the lock up can fall apart and block up other sections of the trans.

IDEA OF A PROBLEM TRANS.
the lock up aplies between 50-120KM/H in 4th gear.
not when water is cold.
not when auto oil is above 150C[there is also a oil temp sender unit inside the trans].
not when at idle or full throttle.
not when the engine rpm doesnt match the output rpm speeds needed.
[slip sencor].or the sencors are faulty.
not when battery voltages are bad,wiring faults or electronic falures[solder contacts in ecu]or when oil blocks interal filters and solinoids.
not when tourque convertor clutch is worn or distorted.
not when the moon is in the sky or not.

ive repaired many nissan patrols that had destroyed the transmision towing trailers.these needed a simple switch to turn the lock up off.
power shift does not cancel the lockup.cutting the solinoid wire would set a code so the power shift light may flash a code.
normal nissan cars normally destroy the rest of the trans and in australia it has always been cheeper to fit a manual and sell the car.

driving a laurel at suburban speeds would cause the lock up the shuttle.
this isnt good its like riding the clutch.
the old L4N71B trans you can use the power shift or overdrive switch to cancel the top gear and lock up with a EL4N71B it can engage overdrive and lock up at a variety of speeds as shift pattern assist is programmed in to the controller.some trans selects 4th gear lock up at 170KM/H as an over speed device and others use the kickdown circuit to hold gears.

if your using the car at hyway speeds it would be better to have lock up working.easy way to test if it is a gearbox problem and not electrical is to probe the solinoid control at the control unit and the trans plugs.

you need to know what trans you have as the early type earth returns and the modern type has power outputs and where the wiring conects to.cruise controls and other devices also imput into the control unit to modify gear change.