Hello all-

I recently bought a 1991 M30 from a friend. 104K, old lady car, with 2 problems. The first is minor - the key will not come out (release isn't triggering). The other problem is that there is no reverse.

After a few hours of testing, here is what I can tell you:

Linkage is adjusted per manual
new fluid
Drive works fine, goes through all gears
It drives forward in neutral
reverse is neutral
Using the procedure in the service manual, I have tested the signal coming to the transmission controller. It shows the correct values for various gears (neutral, 3, etc)
using procedure in manual, overdrive did not report battery voltage to the correct pin regardless of switch position
Car can start in P or N
Reverse lights come on correctly
car will not drive in 1
no diagnostics (overdrive button is broken, but using jumpers to simulate switch. I've tried a number of times, trying both closed and open for the switch)
Overdrive light comes on at start, but goes out regardless of switch position

The car was cheap enough that I have also bought a parts car with a year old transmission. I was thinking that maybe, just maybe, someone will realize that all of the symptoms may add up to something other than pulling a transmission.

Am I on the right track, or should I start swapping electronics?
-rj

Welcome aboard!

I suspect the key being stuck, and the linkage being wonky, are related - and I'd bet it has to do with "overdrive did not report battery voltage to the correct pin regardless of switch position." Power not getting there (or to the key release) would cause both issues.

Is the brake safety switch functioning? Have you shorted it to see if that changes anything?

I'll get some folks who know ATs in here to have a look - hold tight.

The way those transmissions shift into reverse doesn't really have a lot to do with the electronics. I believe even if none of the electronics were functioning it would still shift into reverse just by moving the selector, and the same thing for forward (except I believe it would go into 2nd or 3rd gear instead of 1st) The Q45, J30, 300ZX, Pathfinder, and basically any other RWD Nissan used this transmission, and many times I've seen that reverse is the first thing to go.

Does the shift lock release work fine (lets you shift when you press the brake but doesn't shift when you're not pressing the brake)?

Yea, this sounds like a hardware issue to me. As Wes said, I'm pretty sure the forward and reverse selections are a mechanical selection, not just an electronic one, so if you're not getting reverse, there has to be something wonky inside the transmission. This is issue is also probably why the key won't come out. There's a lock inside the locky cylinder that doesn't allow the key to be removed until the transmission is in park. You may also have an electrical issue as well, but I'll bet this all comes back to the transmission itself.

Ive seen similar problems you've described on various make vehicles and normally there is a transmission mounted range "position" switch mounted to the transmission. It normally is adjustable to compensate for I guess wear of the shift cable. Id just look where the cable that shifts you into drive comes into the transmission its likely adjustable or the range sensor is BAD on the fritz.

If there is no cable and its all electronic. Start swapping parts or stop by a dealership and talk to an old head mechanic. He will give you the fastest solution. If there is anyone left from 1991 or that did repairs in that time frame.

Hello fellow M30 vert owner!

As for the stuck key, I will assume you are not familiar with the unique release button on the ignition, which must be pushed in order for the key to make one more step turn and is then able to be removed. (my apologies if you already knew this, but I must confess it stumped me for a bit after buying my M30)
This only works when the car is (or thinks it is) in park.

It's been a while since I crawled under my M30, but if my memory suits me, there is a mechanical link from the shift to a rather simple lever on the outside of the transmission. It is not drive-by-wire.

From all the research I've done (but with zero hands-on) my armchair diagnostics would be you've got a couple stuck or failed solenoids -- which are an issue for the M30. I know my 1st to 2nd gear solenoid shifts a bit rough when it's cold, but I understand they are easy to get to once you drop the transmission pan (something I need to do eventually). I have yet to hear of an M30 transmission which has failed due to anything besides neglect or solenoid issues.

Just wanted to do a post mortem for anyone else finding this thread in the future.

The ignition key issue was traced back to the control box under the dash. Swapped it out, and now it all works fine.

The transmission was another story. I got the overdrive switch replaced and could run diagnostics, but it came back with no codes, then codes, then random codes. In the end I just swapped trannies - a heavy, filthy job, but not exactly rocket surgery.

Thanks for everyone's help!
-rj

Glad you got it sorted out and came back to tell us what resolved the issue.

Good deal on getting it fixed - Thanks on the heads-up on control box ....

I had my M30 trans rebuilt last year, 240K miles. According to the transmission shop -- there is nothing anywhere that is a direct drop in replacement. This is due to the custom length and rear mount. The basic insides are a lot like the standard Nissan automatics of the day but was made especially for the M30. This is what I was told, I'm not a transmission expert. AAMCO rebuilt it at 180K ... when I went back they said the old guy that worked on the old transmissions retired and they would not be able to repair this old transmission. I found a shop that worked with the national re-builder Certified Transmissions - 100K miles lifetime warranty.. no all I need to do is pass smog check this month....

kentr6727 wrote:All I need to do is pass smog check this month....

I'm glad Washington state doesn't require emissions testing for vehicles at or over 25 years. Although last I ran it through it passed no problem.