Transmission Noise

[BillD]

I have a '73 240z with a '78 280z engine and a '79 280z 5-speed transmission. The tranny makes noise in all gears except 4th. Not horrible, just more than would be expected. It shifts easily, stays in gear, and operates beautifully. Any ideas about the noise?

Thanks

Bill D.

[2ManyZs]

First thing I would do is drain the transmission lube in a large pan and check for any metal shavings.. if you find a lot of metal "dust" in the bottom of the pan, it could be either a bearing or synchronizers....

On the simpler side, it could be just a little low on lube or perhaps you ought to try a better lube.. I usually recommend Redline MTL (manual transmission lube), it is a bit expensive, but it's worth the piece of mind and slightly improved shifting performance.

[Victor Laury]

I usually recommend Redline MTL (manual transmission lube), it is a bit expensive, but it's worth the piece of mind and slightly improved shifting performance

Love this stuff, it's been in My Datsuns for the last 8 years. When I get a new (to me) Datsun, the first thing is new fluids, including MTL for the box and RedLine Shockproof for the diffy. Mobil 1, WIX filters and Castrol brake juice make it a complete set.

I think, but not sure, that it's MTL (Manual Transmission Lightweight).

[BillD]

I would have thought that I would be heading to a heavier fluid (SAE90) in the range because of the age of the tranny and the noise. I've had very good results with other Red Line products, so I'm more than willing to try this one, but was just wondering.

BILL D.

[Gav240z]

I haven't managed to find Redline oil here in Australia for the Z box instead for any Aussies who are reading I've heard GM LUBE is good stuff for the Synchro's.

If you gbox is noisy as in a droning noise it would most likely be bearings. Had this problem with a Z a while back, try driving it slowly down your street or down a hill and letting it roll down this should give a good indication.

[tanny]

This brings to mind a question I've had: How do you differentiate between tranny noise and differential noise? I have a very low volume grating noise(worn bearings noise?) when power is applied in any gear. There is no noise when I let off the gas or coast. Thanks, Victor.

[Gav240z]

In my experience I've found it hard to differentiate myself and currently I have a bit of a odd noise coming from the rear left of my car not sure if it's wheel bearings, uni joints, or the differential or none of the above.

For now I won't worry about it and if the diff blows up (highly unlikely) I'll replace it with a R200 LSD instead of the R180 in there now.

The wheel bearings , uni joints will be done in due time anyway so I guess I'll know better then.

[BillD]

Finally got the car on some relatively level ramps and checked the fluid level. Couldn't find a sqare headed plug on left side but did find one on the right. Added three pints of gear oil to reach the hole and was rewarded with less noise and smoother shifting. I will flush the system this week.

Given the amount of gear oil, is this the correct fill hole for a '79 5-speed? The square headed plug was in just about the expected location on the right (passenger) side and was to the rear of an electrical sensor of some sort. What are the penalties for overfilling the tranny if it isn't?

[Alan Pugh]

Definately sounds like a bearing from what you have described.

No noise in 4th gear is the give away here.

Keeping in mind a gearbox gives you different ratios for each gear, and unless you are in 4th gear which gives you 1 to 1

drive, everything is spinning at a different rpm.

I had a car once that was a 5 speed that I bought from a woman who only ever used the car as a 4 speed, it had done 65000 miles when I bought it and none of those in 5th gear. The bearing noise in 5th gear was terrible when I bought it, but three new bearings later it was as quiet as a mouse.

Alan.

[BillD]

I figured that the whine in all gears except 4th was the give away. It is much less now, but still there so I'll have it checked out.

I'm still worried about the right versus left side of the fill hole. The fill hole I used is on the passenger side (right) of the car just to the rear of what I assume to be the reverse light switch and on the same side as the speedometer cable. Is this correct for a '97 5-speed?

One more question about draining the tranny fluid. Exactly what kind of a tool fits in to the square drive hole in the drain plug?

Thanks,

Bill D.

[kmack]

If I remember correctly (not always a good thing), teh fill hole is on the right side of my 4-speeds. I remember crawling under the car once on the passenger side to fill the tranny...

As for the noise, I agree to it being a bearing going out. My original 4-speed had the same noise. It would only get quite if the clutch was engaged or driving in 4th gear. Unfortunately, I drove it a little too long and it finally gave out. For those with 4-speeds here, be aware that typically the first bearing to fail is the rear countershaft bearing. I've seen 2 tranny fail with this same bearing. Both split the outer race along it's circumference! Very weird.

As for the drain plug, get a 1/2" breaker bar. That works perfect everytime and gives you the leverage you need.

[2ManyZs]

If you put 3 pints of lube in it, I'd say you are looking at a teardown soon. They only hold a little over 3 pints if I remember right. Which tells me the countershaft bearings have probably not been getting much if any lube to them in a while.

How long was the trans run with the lube this low?