bataradena

1993 NA 2+2 with a RE4R01A. (newbie at trouble shooting automatic transmission)
I have a automatic that is slipping only in 3 rd gear at highway speed, only when I punch the gas peddle. Driving less then 45 mph and then punching the gas peddle, not letting the transmission to down shift to second gear, three gear is not slipping. I connected a transmission pressure gauge today. Idle Specification is 60-71 PSI, I'm reading 50 PSI. Stall specification is 148-159 PSI, I reading 165 PSI. During my test drives I'm reading the same PSI when third gear is hookup, not slipping, and when third gear slipping, about 165 PSI. So the numbers suggest the transmission pump is maintaining a good working pressure, no pressure drop-outs in any gear circuit, slipping or not. Any comments are welcome!
Thanks

PredatorZ

Any idea when the transmission was serviced last ? Never a bad idea if you are in doubt to have the transmission filter replaced and new fluid added.

PredatorZ

Found this

Transmission: Automatic Transmission Diagnostic for Nissan 300ZX Z32 (1990-96) Transmission Automatic

PredatorZ

Xenon doesn't currently have a factory service manual download for the 93, but it does have the 94, most likely pretty much the same.

XenonZ32.com Reference

In the PDF "AT", it covers the process above in my last post.

bataradena

I purchased the car about a year ago (110K miles) and the previous owner had the trans rebuilt about 30K mile ago. I knew the trans had an issue when I test drove the care so I thought maybe with so low of mileage on the trans the problem might be with the valve body or the one of the solenoid valves sticking or going bad. I drop the valve body when through all the spools/valve and performed a 25 PSI test to the electric solenoid and nothing was found. After all this (oil was changed / with filter) others suggested I perform a trans pressure test to see if the pump was good or if there was a leak in one of the hydraulic circuits (third gear) before taking the trans apart for rebuilding. Nothing was found during the pressure test other then maybe the clutch plate are toast.

300zx lover

Hi ya i recently bought a 92 zx a/t and it started giving me problems on the transmission i switch the trany fluid n the filter n still giving me the not shifting issue, so i took it to a mechanic n he said that is not throwing enough pressure to shift, what is that i have to fix, any help is appreciated thx.

bataradena

I'm not the expert here but I do have some items for you to check. First let me explain some point of interest. Inside the trans there are two electrical solenoids that control shifting 1,2, 3 and another valve that controls the transmission operating pressure during shifting. The pressure is generated by a pump with a electrical solenoid valve (Pulse modulated) that controls the trans oil pressure (pressure around 75 psi) during shifting which increasing for clutch hold, 165 PSI. If the clutch hold pressure is low < 165 PSI the clutch will slip.
OK, what would I do? Get the Factory Service Manuel (FSM) perform the trans computer check first and if that check "good" then move onto performing the electrical test, checking the solenoid valves resistance. The connector is located right next to the power steering reservoir. Don't forget to check the "Dropping Resistor" which is a "Current Shunt" for the Pressure solenoid located on the the passenger side inside or under the wheel well fender.

Good luck!