Hi. I just purchased my second Z, a 85 turbo with auto tranny. Will post pics once I find and squash this gremlin that plagues me. The car is pretty solid with the exception of one major flaw. The car fires up right away and strong as soon as the key is turned. However, once you let off of the gas after shifting into drive the transmission shifts back into neutral, and will not go back into any gear untill you shut the car off and let it sit for a minute or so. The car will move forward the first time you give it the gas, but after you let the pedal go the tranny goes into neutral once more. This is my first auto vehicle and my extent of troubleshooting is checking the fluid wich does not appear/smell to be burnt and at the correct level. As far as I know, everything in there operates under black magic or some sort of sorcery. So I bought the car as is with this problem in hopes that it would be somthing simple, but alas I am at a dead end. The car has 130k, and the previous owner claims to have rebuilt the transmission 20k ago. The car was parked for two years with no problems, and had no problems untill another guy who was interested in purchasing the car took it for a test drive and the tranny issue started. It isnt an intermitent problem, but happens every time. Anyone have any ideas?

 

Now that is a funny line. I like that.

You say the transmission "shifts back into neutral'. Does the gear selector (stick shifter) actually move and the transmission physically return to the neutral position, or, does it just stop transmitting power to the tail shaft causing it to feel as though it is in neutral? The slush-o-matic operates on the principles of hydraulics (fluid pressures), not "sorcery" and for some reason yours is not maintaining that pressure. Parked for two years? I'm betting a seal has gone bad letting the fluid bypass an area where pressure is required, or, something has clogged a passage-way which is starving the system of fluid. Draining the old fluid, changing the filter, topping off with some fresh fluid, and maybe adding a can of Wynns Transmission Treatment to rejuvenate the seals might get you going, assuming the seller was honest when stating there were no known problems prior to parking.

If all else fails, there is always They practice "Black Magic".

 

no, the shifter doesn't physically go back to neutral(if it did then I would swear it to be black magic). I know that the car was driveable before I looked at it. It was a coworker of mine who was test driving it when the transmission started acting up. He said it drove fine for about a mile or so and after that he had to stop and let it sit for a moment every time he let off the gas. Pressure issue does sound likely now that you mention it. I was thinking perhaps a sensor of some sort on the fritz seeing as how the neutral/park switch fault codes are not retained in the memory on the ecu, and my train of thought was that the car drove fine once you let the ECU reset. However, I cant imagine that the sensor would be able to physically place the tranny in neutral...and with that rambling said... i think im going to abandon that route, cross my fingers, and hope that replaceing the fluid, filter, etc. will do the trick. Thanks

 

We had a Pathfinder do the same thing and it was all because of a clogged filter! I would drop the pan and change the fluid and filter.

 

Do you happen to know any witches or warlocks near by? A local sorcery shop perhaps?

If worse comes to worse, a tranny is not too hard to drop. I'd think it would be cheaper to pull it yourself and then have someone repair it? Filter is usually a pretty easy thing to do. Didn't the pathfinder use the VG30 as well? I'd assume the transmission should be similar.

 

thanks for the insight guys. i will start there first. i feel pretty confident i can handle a tranny filter change.

 

tell us anything you find in the pan. along with break the filter open.

aluminum= hard part failure
needs rebuild
brass= torque converter or any other bushing badly worn
needs exploratory tear-down
"black gunk"= clutches burnt, lock-up(torque conv. apply clutch burnt)
usually rebuild needed(not always)
"any other junk"= problems!!

PEOPLE LOVE TO REPLACE FLUIDS AND ADD TEMPORARY CURES!! nissans needs no additives to use dextron fluids. just because the fluid looks "ok" doesnt mean someone didnt just flush it. flushing a transmission is the worst thing to do. and stay away from ammco! find a old shop where theyve been there for a while. trust a shop that doesnt know the cost till they see inside, unless they have x-ray vision. sorry for the long read

 

Why exactly is a transmission flush bad? Would a flush necessarily be different from simply draining and replacing the fluid?

 

flushing a (new) transmission is as bad. but if you flush an older trans, say after 80k your going to pull all the gunk that holding it together. leaving alot of slack between clutches(going to slip bad) just doing a filter change(drain and refill) is better. should be done atleast every 30k. if theres a drian plug on the converter, drain it too. but i think nissan doesnt put one in.

 

Ok. work has been hectic so I havn't gotten around to pulling the pan and filter yet, but I DID however find out today that the ECU that is in the car right now is one out of a standard transmission car. It is out of the same year model (85. also was a turbo car) but again, the mine is auto and this ECU was out of a standard. could this be the issue? On a side note, I had an oops moment today so....... does anyone know if there is anywhere I can get just the sensor that goes inside the fuel pressure regulator?

 

You have to buy the Fuel Pressure Regulator/Fuel Temp Sensor as a unit. As for the ECU, running a manual ECU with an auto tranny won't really cause any difference. The only slight difference is in the TPS, which had a switch for Full Throttle, but other than that it's not really necessary. I've done the 300ZX ECU swap on my 280ZXT which is automatic. I've swapped between the Manual and Auto ECUs and noticed no difference.

 

I finaly got around to dropping the pan on the tranny. The filter was clogged with some sort of black gunk. I'm thinking possibly a burnt clutch or somthing along those lines. I replaced the filter and low and behold the tranny works now! I'm not going to put to much faith in it though, given the amount of trash that was in the filter. Thanks to all who have helped with this project.