What Tranny Fluid to Use?

[=Resurected280=]

Hello to Everyone Out There!!!

This is my first post that I've made on this site so please frogive me if I say anything dumb :nervous: . I have a 78 280Z with the five speed, all stock, which I pulled out of the woods last spring after it sat behind my house for the last 17 years (this was my uncle's old car) I now have it running awsome and inspected but I have a problem that I have not been able to solve. I just recently changed the transmission fluid and it now shifts hard from first to second gear unless it is very warm out or it has been driven for quite a while. It did not do this before I changed the fluid and all other gears shift fine. The magnet had very little sludge on it and the fluid was fairly clean and the car only has 80,000 miles on it.(I only changed it because of its age) My question is what weight oil do you guys and gals use?(I think this is the culprit) The new fluid I put in is Lucas 80w90, I think. Any help would be greatly appreciated because i'm stumped. Thanks!!!

[Ed]

As far as I know 80W is standard for gear oil. Not sure why it's hard to shift. My old 4 speed did that going into reverse.

[thehelix112]

I'm assuming its an auto then? Thats kind of important to the discussion. Next, what is the car used for? Street/track? Is the engine more powerful than stock so likely to be stressing the transmission?

If you want it to go back to stock I recommend you try the genuine Nissan oil, or at least ask your Nissan dealer what they recommend. If you are worried about the gearbox holding together I would recommend redline stuff. Their shockproof manual box oils have a great reputation (and have held my standard 5-speed together behind my turbo box thus far - keeping my fingers crossed), and the ATF oils are fully synthetic to don't mind a bit of heat while racing.

Dave

[GunnerRob]

According to my 1975 280z owners manual, the gear oil weight you specified is good for ambient temperatures from about -10 deg. F to 100 deg. F. It also specifies using 3 1/8 pints of oil. Hope this helps.

thehelix, he stated:

I just recently changed the transmission fluid and it now shifts hard from first to second gear unless it is very warm out or it has been driven for quite a while.

Also, I've heard good things about Redline products as well.

[hls30.com]

Replace your modulator valve, less than $20, and your problems will go away!

WIll

[thehelix112]

GunnerRod,

So? Still ambiguous to me. Or don't auto's shift from 1st to 2nd? Maybe I was confused by the language.. `shifts hard from first to second' vs `is hard to shift from first to second'

Dave

[Bambikiller240]

Since he's talking about "The magnet had very little sludge on it...." I'm not aware of a magnet on the 280Z auto trans, but I could be wrong.

EDITTED. Guess I'm blind. :stupid:

[hls30.com]

" I have a 78 280Z with the five speed, all stock, "

from the first post-forget the modulator, a 5 speed aint got one!

Will

[thehelix112]

Oops.. hehe.. I'd best be shutting riiiight up then.

If its hard to shift when its cold that would mean that the cold weight of the oil is too high perhaps? So maybe get some 70-90W? That might help. If I've remembered the correct way they label oils.. ?

Dave

[dogma420]

the helix....it's not an auto tranny...if it was, it would be totally hosed with 80/90 in it....80/90 is GL4...that should work fine...

did you fill it until it started to spill out of the check plug?

I used 75/90 gear oil, not much different, this might be the ticket for easier 1 to 2nd shifting, but this shouldn't really make a difference....

You could just try a 2nd change with just 80/90 or go 75/90...got nothing to lose,....just changing the fluid shouldn't cause this problem...if its been a real long long time between changes it might (i say might) make a difference but doutful.

[=Resurected280=]

Sorry I should have been a little more specific. This is a five speed manual, and I did fill it until the fluid came out the filler hole. The car was also level(not just jacked up on one end) when I put the fluid in so it should have the right amount in it. I dont think the fluid would cause this problem either but I wouldnt think the synchros would be this worn out after 80,000 miles. That and it didnt do this when I was running the old fluid in it.

Since this problem started I have changed the clutch and pressure plate and all the plastic bushings around the shifter lever itself. This car also has a recent MSA steel braided clutch line, clutch master cylinder and slave cylinder just as a side note.

Thanks for all the replies!!!

[thehelix112]

It is the job of the fluid to provide a barrier between the synchros and the gears they are accellerating. If the fluid is too cold (or too hot) and hence not operating at its correct weight this will cause the synchros to have trouble. (I think?)

Thats why when the oil comes up to temp the problem goes away.

Dave