Automatic Transmission problem 82 wagon

[oldmax82]

I have an 82 maxima wagon LD28 engine. I had a starter problem the other day and since it was still under warranty at the place which installed it, I towed the car over to the shop, a distance of about 5 miles, maximum speed 35mph.

When I picked up the car yesterday it started just fine but would not shift into high gear. In fact it did not want to shift out of low into second and did so only at about 20mph with a lurch. The fluid level is fine and it looks and smells fresh. This is the three speed jatco transmission with a lock-up torque converter common on this model of maxima.

I asked my helper who drove the maxima when I towed it if the car was in neutral during the trip. He said he could not remember for sure but thought it might have been in drive (D).

I would appreciate any thoughts on the origin of the problem or possible fixes. Before I towed the car the tranny was working perfectly.

Thanks, Terry

[asavage]

First guess: vacuum problem. If the power brakes feel normal, then they probably knocked off a line either to the vacuum proportioning valve on the top of the IP, or the line from that valve to the trans' vacuum modulator.

If you have a FSM, check out pg AT-10, which shows the vacuum schematic.

With no vacuum to the vacuum modulator, the trans "thinks" that you have your foot planted nearly on the floor, and won't upshift until the engine is revved way up, and when it does it shifts at full TV pressure (high & harsh).

If the power brakes feed hard, the vacuum leak is probably upstream of the vaccum valve on the IP, or the vacuum pump itself is at fault (but the vacuum pump is pretty reliable).

[oldmax82]

Al: Thanks for the tip.

I do not have a FSM but I will check vacuum lines from the injection pump and transmission. I'll let you know what I find.

Terry

[asavage]

Cheap FSM on eBay right now, $15 shipped, get it while it's available!

I tell you, I used a canned search for over two years and not one 1982 FSM came up for auction in all that time. In the last year, at least six have come up, and they sell for cheap. I don't know what changed.

[asavage]

I do not have a FSM . . .

Here's the page (click on the image for a truly huge version):



[For some reason, Nissan calls the vaccum control valve on the IP the "vacuum modulator", and the vacuum modulator on the transmission the "vacuum throttle valve". This is different from the rest of the world. In the post below, I call the vacuum modulator on the transmission by "vacuum modulator". Don't get confused.]

IIRC, it's a bit difficult to trace one of the lines, though I don't recall which. This schematic shows that the vacuum control for the modulator is quite different from other rigs (GM and Ford are the other vacuum-controlled AT/diesel combos I'm familiar with, and they don't do it this way). I assume there is a calibrated orifice near the tee at the modulator (on the line to the vac pump). Has to be.

Anyway . . . your symptom would have me looking hard at the amount of vacuum at the modulator, but measuring the vacuum there is not all that much fun unless you can get the car up in the air a bit to connect the gauge, and you didn't look like you were set up for that when I visited you a while back.

If you do want to do that definitive test, jack up the wagon, pull the vacuum line on transmission's vacuum modulator at the transmission (under the wagon), connect a std automotive vacuum gauge, start the engine, watch the gauge and rev the engine up and down. The gauge reading should move quite a bit -- the chart above shows a total variation of 7" to 23", but you probably want to just look for a number above 20" at idle. Any reading lower than 20" (ie 19, 18, etc), and you'll want to check that you have sufficient vacuum available from the vac pump.

Now that I've written that -- and looking at the diagram above -- I can see that you can do this check up at the valve on the IP, which is a lot easier.

The rubber vacuum line at the modulator on the trans is a high-failure item on other rigs. It's gets subjected to mud and heat and does a 90° bend.

If the trans didn't upshift at all, I'd advise looking for a stuck kickdown switch on the accel linkage (above the accel pedal). But I think that the trans will not upshift under any condition if the kickdown circuit is energized.

[oldmax82]

Al:

That was a good call on the vacuum leak. I kept tracing lines from the IP and transmission and could not find any obvious leaks in the rubber hoses. On closer inspection I found a small hole punched in the metal line located just under where the electric shop installed the new starter.

This picture was taken from under the car at the starter. After cleaning the line with brake cleaner the hole is pretty obvious.

[img] I don't think this picture is attached. I don't know how to do it.


After cleaning around the hole I put a small piece of electrical tape over the hole and now the transmission shifts fine. Of course this is a tempory fix. I'll take the car over to the shop Monday or Tuesday to see what the owner will do but I figure replacing the whole line may not be an option. Do you have any recommendations on a permanent fix? Epoxy, liquid metal, rubber plug? As you can see it is pretty greasy under the car so whatever I do it will need to be grease, grime, water, and road dirt resistant.

Thanks, Terry

[asavage]

I don't think this picture is attached. I don't know how to do it.

You can't attach a pic to a post -- this forum software isn't set up for it. The picture has to be hosted somewhere. I can host if for you, just email it to me: asavage@iname.com, and I'll post it to the thread, or I can email you back the URL of the pic and you can post it yourself. In either case, I'd like to see it.

Do you have any recommendations on a permanent fix? Epoxy, liquid metal, rubber plug?

Hard to advise without seeing it, but really anything that is durable will work, as long as the line is still structurally OK. Even several layers of electrical tape will likely be OK for a long while. If sufficiently clean, epoxy might be the easiest, yes.

Glad you were able to track it down, and that it doesn't involve removing the transmission

Hey, since you're a BD brewer, you might be interested in this bag filter I installed three weeks ago at our distribution trailer.

[asavage]

(click on image for larger)


That's an arc-weld hole. They didn't disconnect the battery when changing the starter, and the battery cable off the starter hit the line and melted it. My opinion, but I've seen it before.

Too bad they didn't hit one of the other two lines -- unless I miss my guess, they're the trans cooler lines, and ATF would have been everywhere. I'd like to see them miss that!

[asavage]

Well, Terry, what's the "rest of the story"?