Turbohead

I have owned several 965s which uses the G50 /52 trans. including 3.6Ts.
I have noticed most all have a chatter or vibration when engaging the clutch backing up only. This does not feel like clutch chatter. More like a rumble from trans axel .
I have dropped fluid and inspected thinking might show debris from wear. none found.

Have any of you felt this ? Know what it is ?
Thanks
Elliot

Sifly

I asked 9M when my car was in for some work. Its the LSD making a noise when in reverse and is quite normal apparently?! Never worried about it since.......

Si

Steven C.

My 3.3 is in the shop for a clutch and it had a bad shutter in reverse that came on sudden about a month after I got the car and could be described just as you did. Well today I found out the dual mass flywheel has a split, so shutter explained. 60,000 miles is all the car has on it? Oh well, at least it is explained now and no more fear the tranny was going to fall out of the car?

Black_Hat

I put in a friction modifier last oil change and the noise went away

it was pretty bad before especially in reverse people would look at me funny when I backed up

Turbohead

I ran Swepco and then switch to Delvac it got worse !
What modifier did you use ?
Elliot

Black_Hat

the1st change I used some brand I found at auto zone ..don't remember the name but it worked
2nd change I used redline it worked as well
delvac oil both times

My 1st change I ran without modifier for while and it made a terrible noise

budge96

My 3.6 Turbo would grumble really bad in reverse ,I was told it was either the gear mesh or friction
plates or both but absolutely normal.
I believe it has to do with the percentage lock-up on the LSD,sounds like rocks crumbling!

denver88carrera

My 1991 3.3 had the same issue when I purchased it (at 49k miles). Everything I read in the forum archives said it was normal though the seemed to be more pronounced in some cars than others. Based on forum recommendations and those of my mechanic, I replaced the LSD fluid with Mobil 75-90 Delvac synthetic gear oil and a small $8-10 bottle of LSD additive from the local GM dealership. I recall that it took 100 or more miles for the sound to quiet gradually but the car has been dramatically quieter since and the LSD has never had any problems.

I cannot find my receipt but I think this is the same stuff: http://www.ws6project.com/user_stor/...oducts_id=2250

The description is worth eight dollars by itself: "If you rear end is noisy when turning at low speeds, this usually takes care of the noise."

Kevin

Boeing 717

I bought a LSD friction modifier from the ford dealer, used it with the delvac and it got much quieter as well, but man does that stuff stink, i left a small bit in a cup in my garage and the next day my entire house stunk!!!

Turbohead

So Guys it sound like most G50/52s have this problem to different degrees.
I will try the additive . ...Where is Anthony on this ???
Elliot

GTgears

Just an FYI, while friction modifiers make the LSD quieter, they also reduce how well it functions. If you track your car, you may see a performance difference with modifiers in there. If it's purely a street car and backroad bomber, friction modifier may be exactly what you want to keep the car more refined...

Metal Guru

Using straight Delvac, my LSD wouldn't slip at all so I guess you could say it wasn't functioning in that mode either.
I've been using Mobil 1 LS and am happy witht he sound and performance.
Word is the narrow body 964s with LSD can run straight Delvac with no issues. The 50/52 seems to be a little more fussy about which oil is in it and it must contain some friction modifier.

GTgears

Narrow body 964's run a 40/40 LSD. 964 Turbos run a 20/100 in the G50/52. This is why the problem you guys are describing exhibits it in reverse. It's behaving the same way the LSD does under braking.

Vincent C.

here is the additive we always used with good results.....vinnie

Flachbau

System Normal ... my understanding is that in reverse the planetary shaft is forced against the 90 degree surfaces and that creates a grinding noise. When turning in reverse the effect is accentuated on the inside wheel as it is taking the most pressure. Additives may help reduce the noise by coating the surface so that there is better 'frictional slip' - but that's about it.

Fair Disclosure: Lifted from a Pelican post ...

Just found this description in Frere 'Porsche 911 Story 6th ed'

Its usually the 964turbo and 964RS guys complaining about the noise. Both of those cars used the extreme 20/100 split motorsports lsd.

here is Frere description

The differential of the 964 series Turbos and Carrera RS 3.6 has a locking factor of 20 % when the car is driven and up to 100 % when it is coasting in a low gear. This is achieved by a Planet carrier split into two halves (3), driven by the differential housing (1) but which can move axially to compress the discs (4 and 5) of two clutches, pre-compressed to provide 20% locking. This is independent of the torque, as the Planet shaft (2) abuts against surfaces (C) at 90° to the direction of the force acting upon them. If the torque is inverted, the Planet shaft bears against angled surfaces (B) and pushes the planet carrier halves axially to increase the pressure on the slip-limiting clutches.