G50 trans noise diagnosis help needed

175K911 · 05-25-2009, 07:53 AM

I'm very familiar with the 915, but less familiar with the G50 boxes. Trying to help a friend with a 95 993 figure out what's wrong with his trans. He asked me to take it for a drive and within a quarter mile I turned around and put it back in his garage for the bad noises it was making.

Here's the issues:

First, and most alarming, it makes bad metallic grinding noises on acceleration. Couldn't really tell in 1st or 2nd but once you get up to 50 or so, it's nasty in all gears. Only on accel. Definitely road speed related, doesn't matter whether it's 3rd or 5th etc. Put it in neutral and noise goes away.

Second- from a dead stop, I couldn't get it to go into either 1st or 2nd. Physically couldn't get the shifter past the detent and into that part of the travel. Owner said that started happening a few months ago so changed the trans fluid (doesn't know what the shop put in but thought Redline.) However if I'm in 3rd, I can easily downshift to 2nd without heal and toe. But come to a stop in anything but 2nd or 1st and it won't go into those gears without playing with the shifter from 5th down through the gears while at a stop.

Car is tracked quite heavily, but street driven too. He doesn't know the trans or clutch history and in the 4 years he's had it he's not had to do anything but maintenance.

My first thought with the noise was a pinion shaft bearing or ring and pinion going bad. But the fact that I can't get into the 1-2 gate has me wondering if a shift fork in the trans is failing. I guess either way the trans needs to come out.

But before I subject him to an expensive rebuild I thought I'd throw it out to those more familiar with this gearbox. Any words of wisdom?

dshepp806 · dshepp806's Garage

Many threads here on Pelican on the G50......I love mine but have had no problems at all, thus far.

Hopefully JW (and others) will chime in soon and can guide you as to the next step..sorry I can't help (specifically). I sense a need for a drop/inspection.....

Words of wisdom? 'cash reserves will come in handy"...........

Best of luck,

Doyle

175K911 · 05-26-2009, 05:56 AM

Sadly for my friend, I suspect you're correct. Just thought I'd see if there were any here who know of something unique in these trans types that I could check out for him before that major expense. If it were a 915 box, I'd suggest pulling the side cover and take a look at the ring gear wear for a start.

KTL · 05-26-2009, 09:17 AM

You can pull the side cover on a G50 just as easily. Many do LSD installs in-car this way.

Road speed related is bad. If it was RPM related, it would be cheaper- likely a clutch issue. Road speed says output shaft componentry to me.

The shifter issue sounds like a damaged fork to me. That's why shops like Carquip and California Motorsports sell the stronger 1-2 shift fork like this:

http://www.carquip.com/parts/911/trans/gears/G50gears/g50race/index.asp

G50 needs a few specialty tools to tear down- very long socket (typically made with suitable socket and a piece of pipe welded to it) and a very long gear puller because you can't use the gravity method of disassembling gear stacks like the 915 lets you do.