Infamous G50 Rattle or something else?
 

I'm probably beating a dead horse......

After my 1987 911 Targa is warmed up, I hear a muffled rattling noise that sounds like it coming from the gearbox. This sound is audible only when the clutch pedal is released. When I press the clutch in the sound stops. If I drive in 1st gear and let the motor idle pull the car, I can hear the same sound. I suspected the throw out bearing.

The motor was dropped last weekend. The throwout bearing was replaced. It was failing-made lots of noise when spun. The clutch plate and pressure pad where in great shape, so they were not replaced. The shift fork was upgraded and the guide tube was replaced. I did not replace the pilot bearing.

I have updated the bushings in the shifter and it has the wrap around the shift rod located under the shift coupler access plate at the back of the center tunnel. (Followed the Excellence 'Rattle Trap" write-up) I don't think it the shifter though.

The clutch pad is the spring center type and not the rubber type. Could this be causing the noise?

I have also read about an updated slave cylinder to stop the G50 rattle.

Wil Ferch mentioned this a few years ago - Has anyone tried the updated slave cylinder?

There is a technical "tip"....shown on p.66 of the Parts and Technical Reference Catalogue..that might be worth reading :

"On 911 Carrera's from model year 1987 through 1989, to repair clutch pedal clatter ( noise that goes away when depressing clutch pedal slightly) , a modified clutch slave cylinder should be installed. The new type slave cylinder, part number 950 116 237 11 can be identified by the extended rubber boot with spring installed inside.." ( pic included in reference).

Also...same reference...p.48, there is a shift rod rattle fix described ( too long to repeat here) that essentially adds a fat rubber band ( part 999 701 969 40) on the shift rod.
- Wil

Do I just deal with it like the rest of the G50 owners?

So, what was it doing before the changeout? Slipping?

Sounds like you've got the shifter in proper mod..and thanks for the piece on the modded slave cylinder (rattle? how's that process happen?)

Sounds like it may be mechanical, at this point,..? What? I don't know.

I get a bit of rattle in my 89 but not under load (or lugging). I, too think, mine's to do with a clutch-related problem.

BTW,..what exactly makes this noise with the throw out bearing? [[[[[QUIET=CLUTCH PRESSED]]]]]................ (not the other way around...)???

Best of luck

Doyle

sounds like the "rattle" my G50 makes. It has been like that for 6 years and i drive mine hard ! no problems so far. Would like to hear what others have to say about this but i wouldent worry too much :)

Cheers,

Ed

Mine and two other friends make the same noise. I believe it's transmission main or pinion shaft bearings. But like Ed said, years have gone by with HARD driving and everything is fine, despite the noise.

Some will chime in and say clutch noise. I disagree. Another test is to idle with the clutch released. Push the gear lever a slight bit like you're going to put it in gear, but don't push it far enough to actually begin engaging a gear. I bet the sound goes away. That eliminates the clutch as a culprit and points to gear shaft (and the bearings which support them).

KTL: good point. Mine's as strong as they get....I watched a reputed P-wrench (2 years ago) , while sitting in the seat of newly bought car,..answering my questions as to this noise....he said he wouldn't worry about it at all......normal... I left with that that day,..2 years later, we're OK.

,...however,..I still say she's NOT perfect,...somehow it has to exist, no?

Best,

Doyle

G50 Rattle or Chain Rattle? I've got both. Distinctly different sounding and both dissapear at higher rpm's. 172k on the engine, chain is surely stretched some.

KTL, yep, did that and the noise did lessen.

Today I called two local Porsche shops and they said it was normal for the G50s to make this noise.

Couple things they mentioned;
1. Check the gearbox & motor mounts. Failing mounts might increase the noise. My motor mounts are new (stock), but the G50 mounts are 21 years old and so far the only way to replace the rubber bushing is to use the WEVO repair method.
Hmm, I'm close to WEVO. Perhaps I'll have them replace the rubber bushings with ones as the same softness as the stock rubber mounts.

2. Check the drain plug on the gearbox and look for metal shavings\fuzz. Something might actually be failing.


mthomas58

Does the chain rattle stop if the clutch pedal is pressed? I would think the chain rattle would continue, if it was a "chain" rattle.

I am not sure if we are having the same issue but beside the major issues I posted below, I also have the rattle noice at the transmission once in a while. It could be produced at lower RPM. The rattling noise can be described as you are putting some pieces of metal chain into a metal jar and shake it fast, as the rythm of car running.

http://forums.pelicanparts.com/porsche-911-technical-forum/429066-scary-noise-thump-when-engaging-torque-tranny-clutch-engine-please-read.html

BTW, I bought my car to AASE today and Jeff said it is my rubber disk clutch is gone. Probably the rubber is completely separate from the clutch disk. It need a new clutch disk and new spring center (930-116-014-02). He quoted me $1,3xx. He added it will be more because when the engine/tranny is comming off, there will be more parts need to be replaced. But basically, it's the clutch problem.

No, the chain rattle is only under load, only when engine is hot, and only at 2,000 to about 2,500 rpm, and then is goes away. No chain rattle when engine is cold.

BV,

I don't think engine/trans mounts are going to transmit that kind of noise unless they're completely torn. The mounts in these cars are pretty robust, so it's easy to see when they're failed. The trans mounts can be replaced with rubber- you just have to buy a complete replacement alloy crossmember, which of course is not cheap. And you'll always find some semblance of fuzz on the drain plug magnet. The synchronizers operate via friction and thus some synchro material very fine particles are always going to end up in the gear oil. Plus, if you have a LSD, you'll get wear particles from the friction discs in the oil as well. So fuzz a bit of on the magnet doesn't necessarily mean problems are present. A monster fuzz ball and big metal chunks on the magnet means there's a problem in there!

rnln,

I'd be wary of what AASE says if you do the test I mentioned and the sound goes away. A damper completely separated from the disc would not operate smoothly whatsoever and would destroy itself fairly quickly, thereby killing your clutch operation altogether. But if you think you need a clutch anyway, have them do it. Still, i'd ask to see the clutch disc when they do the work to confirm their diagnosis. All you do is put the rubber damper in a large vise and then twist the disc with a couple of Vise-Grip pliers clamped on the disc itself. You'll see right away if there's any location where the disc damper is compromised. Ask them what else they think needs replacing. I know standard practice is to replace most every clutch component "while you're in there." But there's nothing that says you can't replace just the disc alone and put it all back together. There is no part in the clutch system that is a one-time-use-only part that cannot be reused when removed from the car.

I'm certainly not saying the rattle in neutral at idle is PERFECT. Just saying it's a typical characteristic of these transmissions and it does not mean terminal failure is coming soon. I don't like it any more than you guys. Still, i've been driving my car hard for ~3 years at the track and it's still holding strong, performing well. A friend has 160K (I have 83K) on his G50 and drives it like a top fuel dragster- same noise, no worries of impending failure. He's a automotive tech, so he knows when there's a problem brewing inside a trans.

I bought my 87' with 75K miles, now have 141K miles on the clock and drive hard. No issues at all except for the rattle. I'm going to leave it until I rebuild the entire box.

Thanks for the replies.

Question for those with a G50 gearbox.

What gear oil have you been using?

I'm wondering since this sound occurs after the car is warmed up, if a thicker gear oil, like mobile 1 90w-140 synthetic would help lower the volume of the rattle???

I think it's just gear rattle. Mine does exactly the same thing.

So MANY types of rattles, no? I've time trying to differentiate these "rattle anomolies",

.,.....studying the shifter mech articles,...all made sense,..techniques applied...fresh HW in there......

understanding the idle gear vibrations when placing her at low RPM in first (or, worse, lugging in second,..DD stuff) and hearing this idle gear vibration "rattle".......AGAIN, another "type"....and then:,...the bigees:

clutch-related/TB issues (mechanical).......seems to me that any/all could contribute to silence (?) or not.....this is the area I pay attention to,..from the wrenches at bay here,..for they've been there,..and know from where these noises are sourced......all silenced with clutch depression,..........again,..what "makes" THIS noise? (patience, please.)

SO many threads out there on this.,....what a definitive holostic thing........thanks to all who share this mechanical knowledge. The P-wrench (and others here) say not to worry,..although I ask specifically, what is making this noise (parts?)

I'm up for a fluid change, too. Ordering new HW now.......she sure shifts good now,........so , after 2 years, it's time to change the fluid....


JW had some good threads on this,...

Best,

Doyle

My '87 did this as well if I didn't release the clutch smoothly when starting out or lugged the engine at low speeds. Wasn't there a TSB for a brace to be added to the heat exchanger to address G-50 / HE rattle that was later incorporated into the late '88 cars?

For what it's worth, I have an '86 with a 915, and it makes same noise too. It's only audible when the clutch is released. I have solid mounts all round so the noise is *really* amplified.

JB

I use Mobile Delvac 75w-90 synthetic gear lube. Billed as the Porsche factory fill for all Borg-warner equiped transmissions.
Couldn't find it on Pelican. Do a web search to find sellers.

Thanks, ordered a gallon from here;

http://www.lufteknic.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=Mobil75-90delvac&Category_Code=lubricants

IIRC the 'G' in G50 stands for Getrag. Swepco makes a specific gear oil for these trannies. That and the Delvac mentioned are good.

I don't think this will fix the rattle I'm hearing, but since my engine was dropped a couple of weeks ago, I'm going to give it a shot anyways.

Posted last winter by MBEngineering.

http://forums.pelicanparts.com/porsche-911-technical-forum/378680-engine-vibration-3000rpm.html

Bringing it back from the dead..... I have a 87 new clutch less then 100 miles on it. Car idles little rattle.... It goes away when clutch is pressed in. Driving car is great under throttle in all gears quite as can be. Let off gas sounds like a 55 gallon drum rolling down the street, push clutch in goes away.

If you replaced the clutch disc with a common spring-centered disc, the rattling can become more noticeable. These transmissions were originally used with the rubber-centered discs because the rubber also acted as a vibration and noise damper. The noise is transmission mainshaft and/or pinion shaft bearings.

Ah, the coveted G50. First thing listed when selling the heavy 87-89 cars.

It's noisy when it gets old but it still is much more durable than a 915. A worn out G50 is a lot more manageable than a worn 915. G50 will keep on truckin' fairly well. Eventually a 915 will refuse to work or even worse, self-destruct. That said, i'm very fond on the 915. Straighforward to work on and works great when maintenance is attended to.

No offense, but I'm calling BS on that...the 915 is a racing derived tranny. The G50 was designed to pull the tractor trailer size 87-89 Carreras full of all their luxury add-ons. Think bloated house wife.

There's only one 911 I know of that could break a G50, and that was Eddie Bello. Once it hit 1350ft/lbs of torque, it blew 3rd.

915's break with stout 3.6/3.8's.

So how again is a 915 racing derived and a G50 is not? :)

Nice logic Tippy...the 915 has been around for years, being refined, without gaining weight and complexity. Keep it simple stupid. Think Lotus. Dangerous, but light. Bello's car is cool.

I think by the time they retired the G50/G96 family of gearboxes last year it was pretty well evolved into a modern racing gearbox. Served the 997 Cup Car in sequential form for a decade. SmileWavy

Hi Matt...yeah ok...but I get so tired of the G50 crowd. The new guys and the car salesman types just use it as the one thing that makes the 87-89s special. My 915 is great, after 1st and 2nd gear synchros, new bushings, new wevo coupler.

:D Agreed. I love my 915 and 901/914 gearboxes.

Though if one wants a real race born gearbox he gets a 901. The 915 is what the bean counters made when they refused to give up on Porsche's proprietary split ring synchro for another 15 years when Getrag was already making gearboxes with Borg-Warner synchros that shifted much much nicer.

I guess I jump on this argument too because I'm over 600hp. I HATE worrying about breaking transmissions. The G50 eliminates this 100%.

If I was NA, I could see the benefits of a lighter 915, but I'm not.

Hey Tippy, what year is your 3.2/G50 combo that you turbo charged? I'd like a ride in that.

Like this, Rich ?!?!?!

http://fc07.deviantart.net/fs14/f/20...llixArtist.jpg

Here's Ronnie!

The Moose Knuckle…the larger, less well-known relative of the camel toe…..

Hey Ron, what're you talking about...that's one hot momma!

87. It's a 3.4L now.

Sorry Tippy, didn't mean to spook you. I'm harmless. I do like fast cars though!

Rich, yer not that spooky, bro, and plus, Tippy doesn't scare easily!!! :D

How's it going Matt? Do you like moose knuckles like Colb and Rich do (hardy har har)?!?!?! Want more pics of such??? :)

Ronnie,
You are spooking me! I thought you liked little boys, not big girls...