# 1988 300zx



## jonathancschaefer (Feb 27, 2006)

My Z runs perfect and shifts great(A/T). But recently sometimes it 
will not shift to O/D or it will shift to O/D and then drop out causing high revs.
It will normally shift into O/D at about 46-48mph and 2200-2300rpm. When it drops out of O/D it sends the revs (depending on speed) close to 4000 which
I don't think is good for an engine with 190000 miles. The fluid is clean and I have replaced it every 30000 miles since I got it at 40000 miles. This car has never been in the shop for engine or transmission work. I made some calls to tranny places and got answers from possible temp sensor problems to " fourth gear is gone, you need a rebuild". I'm new here, just wondering if anyone has a suggestion. Thanks.


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## Madmaxfl (Oct 22, 2005)

Before I did the 5 speed swap my 85 had an automatic. It had a power switch and when you hit the power switch it disabbled the overdrive. If yours has the same power switch it may be shorting out or otherwise bad. Something to check that would be fairly easy.


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## z31 (Oct 19, 2004)

it won't shift into OD until the car is warmed up either.

4000rpm at 50mph? Seems more like its downshifting to 2nd than just out of OD.


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## jonathancschaefer (Feb 27, 2006)

Thanks for the advice. Maybe it's not the tranny. I already checked the 
kickdown switch under the gas pedal, it's good. I don't know about the O/D
switch--there is an O/D solenoid in the tranny.


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## Denass121 (Sep 16, 2005)

I have the same exact problem. Usually when its cold its worse, but sometimes it just won't switch to 4th or what ever it should and i'm at around 4k rpm. Then when it gets warm it will shift down. I had my tranny replaced and it still does it. Right now i'm getting a new thermostat cuz mine wasn't working at all. This might actually fix the problem so check to see if your thermostat is working also. I have the O/D switch in my car too so maybe that is the problem also.


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## RocketRodent (Jun 21, 2004)

This is a known issue with the Z automatic. This had my car in and out of the shop last year for 6 months. The tranny had to tore down and rebuilt multiple time until the mechanic found that the issue is with a combination of the last bearing, the seal for it and something else in the rear of the transmission housing. My car flat out would not go into OD after service. Nissan had posted a tech bulletin on this issue somewhere. I'll dig it up here in a bit.

Soo if your not in the mood to have yours rebuilt, I will have a spare, freshly rebuilt unit available here in by the end of this month.


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