Transmission Help--4th not working

[ZohanIsBack]

Hey guys, need a bit of help. I have a 74 260z with an auto transmission. The tranny shifts great, but will not slip into 4th gear. It's literally as simple as that. No weird noises, no grinding. As far I can tell, 1-3 feels brand new.

So my question is whether or not there is a typical problem and solution to fix this, or if the entire tranny is bad? If it is as simple as replacing a bearing or making an adjustment, I'll drop it myself and replace the part. If not, should I get a new tranny or take it in to a shop? One thing I suspect is that this car was dragged at some point because it has triple weber carbs, straight pipes, oil circulator, and direct tank-engine fuel lines (the mechanical pump isn't even being used). Would the guy have removed 4th (IS THAT EVEN POSSIBLE?). Anyway, thanks guys!

[Zed Head]

A quick look at the FSM indicates the the 74 260Z came with a 3 speed automatic. Although, I am new to Z world and could be wrong.

I believe that most older cars came with 3 speeds. But I did have a 1963 Pontiac Bonneville, in 1980, with a 4 speed automatic and a 389. It hauled a@@ for a big car.

[sblake01]

The automatic trans used in the 260Z is a three speed, 3N71B I believe it's called. No S30 ever came with a 4 speed automatic trans.

[Shade133]

he could of messed with the gearing or something to make it shift sooner even at WOT and high rpms so it seems your missing a gear because your toppin out earlier then normal.

[d240zx2]

Plus your axle ratio could have been messed with to make it "seem" like what you describe.

[ZohanIsBack]

And I thought it had four gears. Dangit.....I feel like an idiot now. So it IS working just fine. So my RPMs stay at around 3000 if I want to go 60, but the freeways where I live are 75, and that takes me up to like...3800 RPMs. So that leaves me with two more quick questions:

1. Is it okay to run 8 hours driving at 3800 RPMs?

2. The car heats up to about 230 degrees if I maintain 3800 RPMs. Is this normal? Should I upgrade to keep the engine cooler?

I just have to drive this from Montana to western Washington, but am I stuck going like 60 the whole way?

[d240zx2]

Drive it any speed you can get away with. The L- engines will run all day at most any RPM you choose to drive. The 1 to 2 RPM to speed ratio (3000 to 60)is what a 4-speed manual tranny would produce. Drive it at 80. It's a lot more fun there....

[doradox]

230 is not normal but you don't need to "upgrade" to fix it. Stock components in proper working order should keep your temp at 180-200 in all but the most extreme conditions.

Steve

[Z train]

So my RPMs stay at around 3000 if I want to go 60, but the freeways where I live are 75, and that takes me up to like...3800 RPMs.

That's what my 810 wagon tachs at.It confirms you have 3.54 gears.ANd my temps at 75MPH are around 200-205 with ambient air temp of 105 degrees.

Edited August 26, 2010 by Z train

[Bruce Palmer]

Do you have a graduated temp gauge telling you you're at 230? You are still below boiling with a sealed cooling system so don't fret. And L motors love to spin.

[Pomorza]

In my opinion 230 is a bit hot for the L motor. Where did you get this reading the gauge or something a bit more accurate? I don't think you will have to upgrade you motor just update it. By update I mean flush the system and make sure all the cooling components work as they are made to.

For reference at 75 mph here in Tucson the other day (when it was 105) my Z was running under the midway point of the gauge. Last time i checked it with a thermometer just under the midway point the temp was 185. (*so I'm estimating I was running at about 190 or so)

Jan

[ZohanIsBack]

You guys are a wealth of knowledge! Thanks! I know so much about camaros, but hardly anything about this car.

I am using an after market temp gauge. Graduated, but a cheapie that was on there when I bought it. I am certain it is fairly accurate, however. Yes, I agree it's running too hot. At one point while driving 80, The cap on the radiator let off some serious water all over the hood because of pressure. I think that means it's time for a coolant flush. I might consider throwing a new water pump on there as well. What do you guys think? How can I get this thing a little more cooler? Going 75 I was hitting 230, and I really don't like that.