I figured I'd ask for your opinions on whether or not I have a potential problem. Occasionally, while releasing the ponies and banging through the gears of my 1985 n/a I have to apply a little muscle when pulling or pushing the shifter into the appropriate slots. There is no gear grinding or any other weird noises, just trees rushing by. When moving through the gears in a normal manner (normal speeds) the shifter moves into the slots with only two fingers worth of effort. It almost feels as if the gear slots get narrower (which I know is not happening) and needs me to firmly put it where it belongs.
Has anyone experienced this need to apply "some force" to put the tranny into the proper gear? Is this normal or do I need to check into this further?
Slave cylinder? I've checked and made sure that the clutch pedal free play is at the proper fsm specs.

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1985 300ZX- GLL Dark Pewter Metallic - Survivor

Unless something is actually "bent, worn or broken" the only reason gears would be hard to shift at any speed is due to:

(1) the continuous application of torque to them during shifts. The only way torque could be continuously applied to your gears is if he clutch is not disengaging fully, or quickly enough. At slow speed you are giving your clutch enough time to disengage during a leisurely granny-shift. At high speed a dragging clutch may still be marginally in contact with the pressure plate and still transmitting some torque thru your gears while you try to power-shift.

(2) Worn syncroniZer rings would cause grinding gears regardless of speed, and you say you don't have that.

(3) If you have a badly worn ('sloppy") shifter, it might be causing you to "aim" for a slot which isn't there. Slow shifts might allow you time enough to find gear gates accurately, while split-second shifts with a sloppy shifter might not.

Both early front-engined Ferrari and early Aston Martin had similar problems. Ferrari 'cured' it (not really) by mounting the gear lever in a chrome "gear gate" fixture, which became their signature item. Aston simply replaced the horrible Moss gearbox altogether.

Put your gear lever into each gear and check it for excessive side-to-side motion. PreZident Phil pulled his 1981ZXT gear lever apart a few winters ago and found a broken donut bushing ring trying to hold the shifter accurately. As soon as he replaced the broken ring, his shifts became far crisper, more accurate and smoother. I'll try to find his post and share it here, but I don't recall which year he did it. The neoprene donuts only last so long, then they stretch or break.

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1970 240Z

This is a good discussion about it (altho I'm still searching for Phil's post):

http://www.zcar.com/forum/10-70-83-tech ... ifter.html

http://www.atlanticz.ca/zclub/techtips/ ... index.html

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1970 240Z

When you say "banging through the gears", are you power shifting? No clutch?
The gear shifts will be harder to execute if you are under full power when shifting, especially if you are not clutching in a timely manner. Bad master or slave cylinder could also be the problem. Do you have the proper gear lube in the tranny?

I have replaced my slave cylinder twice and the master once in the 45 years I've owned my 71Z. The problems were similar but with the added problem of not being able to get in gear without grinding.

Not sure this helps.

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John Kish
1971 240Z - original owner

Frank. It makes sense what you said. I can always count on you to reply with some sound advice and your mechanical prowess. I'm in awe of all that stored information that you poZZess.

Thanks
Howard

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1985 300ZX- GLL Dark Pewter Metallic - Survivor

Hi John. I don't think I was power shifting (if power shifting means getting the rpm's up high and then trying to slip into the next gear without using the clutch). I've never done that successfully. I was however under full throttle when I was shifting and I believe that the proper fluids are in the tranny. But I can't swear to it.

Thanks for your input.

Howard

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1985 300ZX- GLL Dark Pewter Metallic - Survivor

After doing some research and asking questions on Zcar I think that I'm going to change the Nissan transmission oil to Redline MT 90 75/90 Synthetic. This should allow better movement of the "cone" (according to other owners). Not that I know too much about how that works... but it can't hurt to change the fluid to a synthetic that everyone seems to be praiZing.

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1985 300ZX- GLL Dark Pewter Metallic - Survivor

Thats what I run in my Z and I have never had any shifting issues.

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W.Karl Walton
Somers CT



75' - 280Z - HLS30203249 - #304 Gold Metallic (stockish)
96' - 300zx TT - JN1CZ24d3TX960293 - Black on Black (enhanced)

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Justin
1986 Z31 NA 2+0

Howard, I know we have different year gearboxes but I was also wondering how many miles you think might be on your throwout bearing? Mine had about 20 years on it before it began 'singing' when I depressed the clutch, then it sort of froZe up and made my shifting balky until I changed it.
I actually had more YEARS on it than I had miles.

Frank

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1970 240Z

Frank, to answer your question -Zee car has 32,800 miles on it so that should equate to approximately 32,800 miles on the throwout bearing, if my math is correct. LOL I don't even know if it is even possible for it to be the bearing with this type of mileage.
Seriously though: I think that any imagined issue that I'm having should be resolved after the transmission fluid gets changed to MT-90 and I learn how to shift more efficiently. I really appreciate your input, so keep it coming.

Howard

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1985 300ZX- GLL Dark Pewter Metallic - Survivor

Well, if you ever have the occasion to either drop your gearbox or pull your engine out, be sure to spend a spare $40 for a new throwout bearing. I stared at mine for about a month while my engine was out, but because it had given me no problems (at all) I didn't change it ("if it ain't broke...."). Less than a month after the engine was put back in, the bearing started 'singing' when I shifted, and by the time the engine was pulled again 4yrs later, the inner race would hardly turn inside the outer race. That was slowing down my shifts in two gears. As soon as I replaced it, I was shifting like Jack the Bear.

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1970 240Z

Frank. I would definitely take your advice and change the throwout bearing if and when I have to open up the trans or engine. Makes sense. But looking forward to that "occasion" is somewhat scary to me. Almost like looking forward to a colonoscopy, if you know what I mean.

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1985 300ZX- GLL Dark Pewter Metallic - Survivor

Howard, if you do change the fluid (recommended if it's 30 years old) make sure you get the correct GL rating for it. For example, the Borg Warner T5 in the 84 Turbos likes GL-4. Using GL5 will destroy the synchros, due to their material.

Good advice.

And if I might add one more suggestion, it would be this: since your ZX left the factory, several after-market companies have introduced magnetic gearbox drain plugs. I believe in those completely and recommend you invest $3 to ensure that any metallic bits stop floating around in your moving gears and adhere to the magnet in the bottom of the case. When you pull the plug again, it also gives you an immediate idea of how things are going inside your gearbox. A clean magnet is a good sign. One covered with tiny metallic chunks tells you there's a problem.

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1970 240Z