Again, I need 1990 Auto transmission help!

bgeshel · Jan 21st, 2005, 11:53 PM

A while back, I started a thread regarding the trans in the 1990 4 cyl auto extended cab, I just bought out of a farmer's field, here in Oklahoma.

One individual sent me to a site to download some PDF files for troubleshooting Nissan auto transmissions.

Well, when I went to utilize the information, I found that my Nissan doesn't have an auto trans control box...nowhere that I can find on the truck...not even under the right seat????

Was there a mid year change? What resources are available to help me with this transmission? The Haynes manual I have would be better used as bird cage liner than a technical reference for Nissans!

There are only four wires (two pairs) entering the transmission. there's no "power" button or indicator on the dash...this truck does not have an electronically operated transmission!!!! However it does have OverDrive!

Hep me, hep me, I'm drowning in ignorance!!!

aaronford · Jan 22nd, 2005, 08:40 PM

Wow, wish I could help. I rebuilt my manual tranny, but the auto is a totally different monster. What is the tranny doing (or not doing)?

**88pathoffroad** · Jan 23rd, 2005, 05:11 AM

Most of the 87's came with a 3-speed auto transmission with no OD or Power option. Perhaps someone swapped in one of those before you got it. The tranny computer is located in the rear cargo area on the passenger's side behind the plastic wall panel under the rear window.

bgeshel · Jan 23rd, 2005, 06:17 AM

The truck is an original, unmodified 1990 extended cab Nissan. 4 cyl w/auto transmission. The truck is equipped with overdrive, but no power button, or indicator on the dash. There is an overdrive indicator on the left side of the dash...it does operate in response to changing the position of the overdrive button on the shifter.

In 1st gear, it seems like the truck is in overdrive, very sluggish acceleration. In 2nd, it's very sluggish at first, then seems to "downshift" and accelerates fine. In 3rd gear it is very sluggish. Reverse is fine!

At speed, the truck never seems to be in high gear. The engine RPM is too high (by ear, not by reading a tach). It also never changes engine RPM when overdrive is engaged or disengaged. There doesn't seem to be any ability to downshift into any passing gear from any forward gear.

When I dropped the trans pan, there was little to no debris in the pan, just some very fine metal "dust" attached to the magnet in the pan. The pan was very clean...much, much less crud than I would have expected for 138,000 miles. The fluid barely has a burnt look to it. Matter-of-fact, it had the smell of cow crap...not the normal "nutty" smell I've encountered in the past with auto trans.

The fact the pan was so clean, leads me to believe that there is no major component failure...just some solenoid, broken wire, etc.

When I move the shifter from P to R, then N, I can hear a relay operating...indicating the start inhibit works...as indeed it does.

The following describes the transmission connections:

1. Mechanical speedometer connection (cable).
2. Mechanical passing gear connection (cable).
3. In and out trans cooler connections.
4. Mechanical shifter mechanism (with no inhibitor switch on transmission..remote location).
5. Only two wire pairs enter the trans. One par goes to a solenoid I can see on the bottom of the valve body. the other pair disappears over the top of the valve body.
6. Fluid fill tube.

As I said, this is an original vehicle...nothing has been replaced or modified.

I cannot find a trans controller box (computer). It is not under the right seat!
(I will look at the location you mentioned!).

My gut feeling is that the overdrive is engaged all the time...this would account for the sluggish acceleration. that would then lead me to believe that a relay or solenoid is malfunctioning...because, as I mentioned, the overdrive button changes nothing except the condition of the light on the dash.

There would seem to be a contradiction in my description of symptoms. I can explain this by assuming the trans never shits into 3rd gear...but remains in 2nd gear with overdrive engaged??? Does that make sense?

The transmission has no leaks, anywhere! The outside is dry as a bone!

Does anyone have any test procedures, illustrations with parts, and parts location identification, computer self diagnosis info, etc.?

Thanks for your time and efforts.

Bob Geshel
Hitchcock, OK

bgeshel · Jan 23rd, 2005, 12:12 PM

I was reading my Haynes manual...I know, what a waste of time!! And I came across something I didn't realize before...the torque converter is a lock up type of converter.

Could it be that the converter is in a "locked up" condition all the time???

**88pathoffroad** · Jan 24th, 2005, 02:34 AM

Oops, I should have said...on a PATHFINDER, the transmission computer is in the rear. Sorry about that. Check inside the passenger's side plastic kick panel up front under the dash.

Sounds to me like your torque converter is staying locked fulltime. That'd account for the sluggish response, but not really for the high RPM's at highway speed...

bgeshel · Jan 25th, 2005, 09:57 PM

Quote:

Originally Posted by 88pathoffroad

Oops, I should have said...on a PATHFINDER, the transmission computer is in the rear. Sorry about that. Check inside the passenger's side plastic kick panel up front under the dash.

Sounds to me like your torque converter is staying locked fulltime. That'd account for the sluggish response, but not really for the high RPM's at highway speed...

I'd not looked under the kick panel...I'll try that next!

If the converter is locked...and the trans isn't shifting up to higher gears, then the high RPMs would be correct...just another problem to figure out and fix!!!! Would the locked converter prevent the RPMs of the engine rising to the point that the trans wouldn't shift up???

Do you have a source for earlier trans diagnosis and repair?