The 510 Realm

Had my 5-speed (FS5W71A) tranny rebuilt a few months ago. The transmission came from Pick-n-Pull last year and was really noisy when mated with my car's stock L16 at that time, which is partly why I had it rebuilt. Good mechanic, reputable shop. That's not a guarantee I know, but I trust them.

Put about 100 miles on the rebuilt tranny a couple of weeks ago, with it mated now to my fresh L20B. The oil in the tranny is GM Synchromesh, which I've had excellent results with in my Mazda3 and also in my MGB. But this tranny was still a lot noisier than I thought it should be, considering all new bearings. And the pattern of noise seemed odd too. So I decided to investigate.

Step One: I pulled the tranny cover-plate (around the shifter) and went for a drive. As I suspected already when the cover was on, the noise was much worse when cornering one direction than the other. Turning left = lots of noise-- hard to describe, but sort of an irregular and squeaky "chatter" that sounded to my relatively inexperienced ear like bearing noise. Turning right = very little noise, or even none at all.

Step Two: I went for another drive while carrying a hefty screwdriver with me. Levered on the trans case just below the shifter (back end of the tail-stock I guess) while driving straight ahead. Sure enough, I heard the same double pattern as when cornering. Pry the transmission to the right (as when turning left) and the noise got much worse. Pry the tranny to the left (as when turning right) and it disappeared.

Step Three: Jacked up car, looked at the tranny mounts. I'm using the Experimental Engineering 5-speed crossmember, which has very little lateral (left-to-right) movement and "seemed" to be pretty straight in that regard. But the factory mount that goes between that crossmember and the tranny itself was noticeably offset in one direction where I'd bolted it to the transmission-- about 2 mm to the right of centre. So I straightened that up as well as I could and drove the car about 20 miles to give it a good test. Much less tranny noise than before. In fact, very little at all.

At this point I figured I had the problem licked, based on two premises. (1) When the back end of the transmission had been offset to the right, I think the driveshaft had been "pulling" the tranny tailshaft (I suppose?) toward the car's centreline, causing the bearing noise that I was hearing. (2) When I had turned a right-hand corner, or when I had pried the tranny to the left, the mis-alignment between the driveshaft and the tranny tailshaft had disappeared.

Step Four: Re-installed the trans cover and shifter boot and drove to & from work again, another 20 miles or so. Noiser again, not as bad as at the beginning but still really irritating. Much of the time the tranny is now completely quiet and runs very smoothly, both driving straight ahead and on right turns. Sometimes I didn't notice noise on left turns either, but every once in a while it would start making those little squeaky bearing-like noises again, especially on left turns but sometimes going straight too.

Apart from the noise itself, I'm afraid this is not terribly healthy for my "new" transmission.

What next?

Two mm is about two thicknesses of thumb nail, you must mean two centimeters. If moving 2mm changes something then it was a loose bolt you tightened when putting back together.

See if something is rubbing the case. Exhaust? Mount tight? engine bolts to case tight? shifter rubbing body?
The trans may be rebuilt but the monkey motion shifter is aptly named. Is it just worn shifter component(s) does pulling sideways on shifter change anything?

You said factory mount as in the original 510 trans isolator? Because when I got my trans cross member from Dave Carroll he said I needed to use a trans isolator from a 240Z. You may want to check and make sure you're not up against the brake line that runs to the rear brakes.

Thanks guys. Mike, I did mean 2 mm-- that's only how far "out of alignment" the trans mounts were.

And I'm pretty sure it's not an issue with anything rubbing against the trans case either; this is clearly a "rotational" sound, not a chafing or rubbing sound, if that makes sense. This isn't the only reason I say so, but the sounds disappear completely when the clutch pedal is depressed. Again, this suggests that whatever is causing this issue is within the transmission, not between itself and anything else.

The shifter isn't the issue. Its pin and bushing are tight. Applying pressure to it does nothing at all. The pressure I talked about applying with the screwdriver is only to the side of the trans case itself, below the shifter.

Three-B's, I am using the 280Z mount that came with the transmission. It fits perfectly. And no it's not rubbing against the brake-lines either; they're well out of the way.

I appreciate these questions. What I'm mostly wondering about though is whether my reading of the situation seems right-- namely, that a mis-alignment (side to side) between the transmission and the driveshaft could cause this kind of rotational, bearing-like noise. Because it dissipates when pressure is applied to the side of the tranny, this is about the only "scenario" I can come up with that makes sense.

But does it really? Am I on the right track? Let me know!

If you measure the location of the transmission and remove it and put it back in I doubt very much it will be within 2mm of the old location. Two mm will have virtually zero effect on driveshaft alignment or anything else. Two mm on a shortened 510 driveshaft (I assumed the sedan as it's the shortest) is 1/16 th of a degree at the differential.

Engine/trans bolts tight?

Driveshaft was shortened.. balance weigh fall off?

U joint?


You may have to just turn the radio up.

It surprised me a little that nobody picked up on my hints about the tranny making these noises itself, internally. I was sure that that was the problem. But the fact that nobody saluted when I ran it up the flagpole got me thinking the whole thing through once again. What if I'm wrong about my premise?

It took a while to find the time but yesterday I finally opened up (lengthened) the hole around the shifter just in case you guys were right. This was the only place that contact seemed even remotely possible between the tranny case and any parts of the body / mounts / etc. It still didn't look like the clearances were tight enough to make this the actual problem but hey, my original hole was quite a bit smaller than the cover-plate that in turn provides the mount for the shifter boot, meaning that I had room to spare. So in the absence of any other brainwaves that became the plan.

And as you can probably guess, it worked. Problem solved. No more "rotational, bearing-like noise" when going around corners, either direction, nor straight ahead either. Yes!

So once again, thanks for the good advice and gentle steering toward the right solution. The Realm rules!

Of course what I'm noticing now is the occasional knock of my brand-new, lovely-shaped Y-pipe against the projection on the side of the block....

Yeah, but you already know where the new noise is coming from (or do you? ) That's an age-old contact point, and nothing a little hammer work won't cure.

As our old mounts either get too hard, or, too soft, it is amazing how much stuff will move when under load from the motor.

One trick we did to really firm up the trans mount, as it moved so much under full on race mode, was to fill the mount with silicone. That helped do the trick along with a steel shifter bushing.

OK, it's a year later and I'm still chasing squeeks & rattles from the drivetrain. Had a lot of success this summer eliminating some of them, but not all.

It turns out that the brake and clutch lines that run along the firewall were banging against the firewall-- and each other-- when going over bumps. That sounds obvious and simple in hindsight, but you wouldn't believe how much trial and error it took to figure this out. (Or maybe you would believe it, if you've done this kind of "sorting" yourself....)

Now I'm back to the issue I started this thread for, a year ago. Keith's comment below sparks another question:

bertvorgon wrote:As our old mounts either get too hard, or, too soft, it is amazing how much stuff will move when under load from the motor.

One trick we did to really firm up the trans mount, as it moved so much under full on race mode, was to fill the mount with silicone. That helped do the trick along with a steel shifter bushing.

What I'm wondering about as a remaining source of my unwanted noise, especially when turning LEFT-- is whether my motor-mounts are indeed too soft... or too hard... or maybe even the wrong height?

I've used two different heights and I think the noise has been similar with both. Last year I was running "medium height" mounts (below)-- about 38mm in height. They seemed pretty soft though so I changed them out for what seemed to be a somewhat firmer set. They're also old, though. And they're also a bit shorter than the previous set, only 36mm in height. (Because they're still in the car, I couldn't get a picture showing the caliper...)

Now, I've got a third set too, brand new from RockAuto, but they seem much too high-- 45mm. As the pictures show, their steel plates are also pretty flimsy compared to the factory ones. But my main hesitation about installing them is the height. I'm guessing that they'd lift the engine too high, to the point that perhaps it would hit the hood (it's an L20B)... or maybe even make the tranny interfere with the tunnel? Anyway: Does anybody know what the motor-mount height is supposed to be? And-- where can a good, proper-height set be sourced? According to my local Nissan parts guy, they're NLA from Nissan Canada...

You run an L20B, right?
My initial reaction to the taller mounts is more cosmetic - hows you hood to valve cover clearance? So may 510's out there have a nice little buldge on the hood from making contact with the valve cover ever time the hood is closed.

That would be my biggest worry.

I slotted the mounts on the motor mount when it bolts to the block to lower my engine over 1/4", and I have about the same clearance between the oil pan and the front X member. 12 years on it now, still in the same position! These were new Nissan mounts when installed.

Byron

NOS mounts were still available in the States recently (last couple years). Nissan is the only place I've seen with OE-style/height mounts. All aftermarket mounts I've bought or seen were like the one you pictured - super-thin metal with super-thick rubber. The 1/4" metal sheet on the OE mounts were total overkill, but still.

all those mounts look like junk. I got new mounts from nissan 4 or 5 years ago for $50ca. it would be worth investigating.

I'll toss in a transmission noise experience I had that might help us understand the challenges of noise isolation. Yes it's in a Z, but I have the usual FS5 trans.

I had an ever worsening 3rd and 5th gear "whine" one road trips. Well not just road trips, but when you spent time on the highway. Very annoying to the point where I started driving in 4th all the time while I decided when it was time to get this thing rebuilt or replaced.

While waiting for that inspiration, I decided to try something I've always wanted to try, which is to built a "T" handle shifter. I found that my hand would tend to slip off a round knob at certain inconvenient times during spirited driving, not sure why, probably just me, but off I went to built a T handle.

When I got the point of installing it, I removed the old shifter rod from the trans and what did I find but one bad/beat up bushing on the cross pin. Interesting. I installed the new T handle rod which consists of a roughly 1/2 or 5/8 diameter steel rod about 5 inches long welded to the top of a cut off shifter rod. Let me tell you it was fun installing the inner and outer shifter boot, but it works. Stuck new pin bushings in (actually old stock ones...) and put it back together.

in the subsequent drives I was busy testing and evaluating the T handle shifter feel and position (got the T handle about 5 deg too far CCW, rats), but it was several days before I finally realized that the trans whine in 3 and 5 was 100% gone!

Since the only thing I changed was the bushings and different handle mass, I can only conclude that it seems the noise I was hearing was just NORMAL trans noise that getting transmitted to the cabin via the shifter rod. So just by changing the reasonant frequencies and coupling, poof! noise gone, or more specifically, it remained isolated from the cabin.

Now don't get me started on the many cases of poly-urethane bushing induced diff/trans whine from moustache bar and trans mount experiences!

Jim, your story is a gift because yes, this is exactly the same kind of thing I'm chasing as well. For me, there are 2 things pointing me (at the moment!) toward motor mounts:
1) the noise increases as my rate of acceleration increases-- that is, at gentle acceleration there's none, at moderate there's some, and at full throttle there's lots;
2) the same progression takes place depending whether I'm turning right (no noise at all), going straight ahead (some noise), or turning left (lots of noise).

This is only a deduction, and maybe my reasoning is wrong (I've chased plenty of phantoms already), but to me all of this is suggesting that the motor is shifting on its mounts, in the first case due to its own torque-induced rotation and in the second case due to the turn-induced centrifugal forces.

Robin and Julian, your comments about factory motor mounts motivated me to get ahold of Chad at Chico Nissan a couple of hours ago about ordering some. He can get them, and readily agreed to ship them to me. What a helpful guy!

But then I also called my local Nissan dealer just to make one last check on their availability here. And to my great surprise, yes they can get them. The last time I checked, Nov 2013, I was told they were NLA. Not sure what changed, but in any case they ought to be here on Thursday, which is awesome!

So I guess that's the way forward at the moment. New, factory-spec motor mounts... and then we'll see.

One trick I did, re noise transmission up through the shifter, I did two things. I cut a "foam cone" that fit inside the shifter boot, and put some foam around the shifter where it comes out of the transmission. This both made a huge difference in sound and the foam around the shifter boot grabs any oil that weeps out of the shifter. I just change it out periodically. Just use a soft foam as to not put any resistance in the shift itself, I used that crappy yellow foam, works great.

I also use a very HEAVY grease on the shifter pin, this helps absorb any vibration as the pin wears. We ( Andy ) made steel bushings for the shifter pivot, which makes an amazing difference in precision of shifting when things are under load.

Also make sure that plastic bushing at the bottom is in very good shape, they were still available a few years ago.