justinmc

Ok... just changed auto tranny's in my 240 (89 SOHC)... The transmission doesn't seem to want to "maintain" RPM's when I let off the gas in any gear...

i.e. I'm driving with my foot in it at 40 and RPM's are at 3K.. I let off and the RPM's drop to 1K... step on the gas and they go back to 3K and the engine accelerates.. not slipping.

Anyone have this problem in their 240? I was wondering if it could be a pressure solenoid or a tranny ECU gone bad.. (as advised by a friend who does tranny work)....... thoughts?

thanks folks

rudeboy

does the tach just drop or does the actual engine revs drop?
our manual trannies are all mechanical except for the speed/rev/reverse sensors...
no solenoids in the manual tranny.
the ecu has nothing to do with the manual tranny except recieve sensor signals

::edit::

if the engines rpm fell that fast you would slow down really quick..
i think your sensor is messed up
only reason i say this is because you didnt mention the car actually slowing down...
did you swap the sensors off the tranny?
was the sensor visably damaged?

justinmc

Ummm the car is a AUTO.. not 5spd.. thanks for the thoughts..

I'm pretty sure its the transmission "shift control module" as Nissan calls it.. I'm in process of getting one and putting it in...

BTW just for your reference.. it is the actual engine RPM's falling not the tach just reading funky... FYI the engine RPM isn't read from the speed sensor in the tranny it gets its signal via the tach (or in DIS cars from the ignition control module)..

rudeboy

guess i was really tired last night huh....i guess i thought you converted to manual when you said you changed trannies
oh well.....
good luck with the auto...
just buy my manual conversion

and there is a tach signal...but only for my car

justinmc

LOL!... glad you didn't think I was being rude.. I come from a pretty deep automotive background.. I was just trying to "BBS" trouble shoot without having to do alot of leg work hehe..

Anyways... mmm whatcha wanting price wise for that whole swap? I'm not really looking (figured I'd wait for the swap until I get the front clip next spring.. just doing some housecleaning and straigtening out the body this winter)...

Oh... btw pretty damn sure its the tranny shift control module... I unplugged it and the trans did the same thing.. basically only shifting when line pressure mandated it.. no OD working, no reverse lights, etc... fun huh? Oh well apparently there was a change in modules in 92.. I've got a 90 SOHC.. but I'm running a 92 tranny.. so I'm getting a 92 module (plugs should be the same.. probably just programmed a little different in 92-94)...

I wonder if it has something to do with sport/luxury mode or something like that becoming available.. I know the maximas started having this option on their auto-sludge boxes sometime around there...

fist

dude thats what an autop tranny with overdrive does...you were probably driving without overdrive before...and then you have it on now?

95_240SXSE

dude thats what an autop tranny with overdrive does...you were probably driving without overdrive before...and then you have it on now?



When OD is on, the revs are maintained more easily, when OD is off, the revs drop faster...if u look at a manual tranny, why do u think people downshift when stopping, in lower gears, the revs drop faster allowing the drivetrain/car to slow down faster...OverDrive is nothing more than a taller gear, which is like cruising in 5th rather than 3rd or 4th in a manual...engine speed is maintained easier...