993 G50 Adventures

yelcab1 · 08-29-2025, 09:32 AM

I have on my bench a misbehaving G50 from a 993. It was stuck in one shift plane. After an afternoon of disassembling, I found the cause.

Item 9, named the bearing shaft, is broken. It allows the deflection lever (shaft housing) to move around and the guide pin is misaligned. While the shaft is easy enough to change, I would like to get some idea of what should be a minimum and reasonable refresh to put the gearbox back together.

This thread will be my rebuild thread. Thank you.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by yelcab1

I have on my bench a misbehaving G50 from a 993. It was stuck in one shift plane. After an afternoon of disassembling, I found the cause.

Item 9, named the bearing shaft, is broken. It allows the deflection lever (shaft housing) to move around and the guide pin is misaligned. While the shaft is easy enough to change, I would like to get some idea of what should be a minimum and reasonable refresh to put the gearbox back together.

This thread will be my rebuild thread. Thank you.

It's been decades but I vaguely remember an update for that part, maybe from GT gears?

john walker's workshop · 08-29-2025, 10:12 AM

The trans was probably working fine, so why tear it down for possibly no improvement? Easy enough to fix the shaft issue and be done. Just a thought.

yelcab1 · 11:58 AM

Well, the front nose is already disassembled so at least maybe those syncros ...? It does have 125,000 miles. There was a lot of brass glitter in the very black oil draining out .... What bearing is worn, I wonder.

Matt Monson · 08-30-2025, 05:18 AM

Quote:

Originally Posted by Bill Verburg

It's been decades but I vaguely remember an update for that part, maybe from GT gears?

I no longer make it. Factory replacement is the only option now.

kevingross · 08-30-2025, 11:15 AM

I believe the upgraded, RS version of the part is 950-303-134-05. The assembly is a bit fussy to put together but not too difficult. Good luck w the repair!

yelcab1 · 08-30-2025, 04:13 PM

$400 ... Ok,

yelcab1 · 08-31-2025, 02:31 PM

I wish to replace the syncros on the 1st and 2sd gear. That requires removal of the shift fork with the slider. Can I cheat and punch out the two roll pins holding the shift fork in place on the rod and leave the rod on the box? Or is it easier to remove the rod/fork as a unit and deal with the spring-pin-ball disappearing act?

dannobee · 09-01-2025, 05:37 AM

Yes, you can knock the two roll pins out and pull off 1st and 2nd gears without removing the bearing retainer/shift mechanism plate. 3rd and 4th shifted ok?

kevingross · 09-01-2025, 06:33 PM

Quote:

Originally Posted by dannobee

Yes, you can knock the two roll pins out and pull off 1st and 2nd gears without removing the bearing retainer/shift mechanism plate. 3rd and 4th shifted ok?

Yeah, probably. But because you're going to be disassembling the tensioning plate to replace its bearing shaft, I would suggest removing all the rods. They will just get in the way, and they are not difficult to reinstall. Just keep an eye on the interlock detents.

yelcab1 · 06:41 AM

So if I remove a shift-fork-rod, is the detent going to fly out into the crevices of my garage?

I'm pushing the pause button for a few days while I am putting the list of replacement parts together. So far, 2/3/4 gears are possibly being replaced for closer gear ratios. Which also means some sliders and most syncros. There is also talk of LSD (the diff not the drug). When the budget is all back together, I will need to continue disassembly of the gear stacks.

dannobee · 09-03-2025, 07:23 AM

Yes, there's spring tension on the shift rods.

And as Kevin said, your broken part will be "fussy" to reassemble (In your pic we can see that the shaft is broken). Ball and spring #10 and #11 will be fighting you. Also, do NOT mix up springs #13 and #14 on reassembly.

yelcab1 · 09-03-2025, 07:53 AM

Broken in two places and the washer / spacer on top is destroyed.

yelcab1 · 09-03-2025, 07:56 AM

Quote:

Originally Posted by dannobee

Yes, there's spring tension on the shift rods.
....

Yes spring tension is there. But is the inch long detent going to drop into the differential housing area? Or is it going to drop down and then stop so that it is visible at the hole?

yelcab1 · 09-03-2025, 09:44 AM

Does this picture mean the input shaft with its 4/3/2/1 gears come out assembled in one unit?
And that the gears 4/3/2 come sliding off the shaft to the left, and not to the right once the whole assembly comes out?

dannobee · 09-03-2025, 10:08 AM

If you're replacing the 3rd and 4th gears, just take out the whole shebang out by removing the 12 nuts holding the bearing retainer plate to the case. Both shafts will come out along with the bearing retainer plate. It is heavy, so be mindful of that. And note all of the pinion shims. At that point you can remove the other big nut on the input side, then disassemble the input shaft. 1st gear drive gear is part of the input shaft and does not come off. Then you can disassemble the retainer plate and shift mechanism and lay everything out on the bench. The detents themselves are not spring loaded, but will move if you start moving the shift shafts around.

The factory tool for removing the nut on the input side is a big long tube with a socket on one side and 1/2" square drive on the other. You can use a big wrench if you can hold the shaft by using an old clutch disc in a vise.

yelcab1 · 09-03-2025, 10:22 AM

So the work just ... triples.

Matt Monson · 09-03-2025, 11:12 AM

Quote:

Originally Posted by yelcab1

Does this picture mean the input shaft with its 4/3/2/1 gears come out assembled in one unit?
And that the gears 4/3/2 come sliding off the shaft to the left, and not to the right once the whole assembly comes out?

Yes.

I spoke with Michael a bit last night, and based on his production date, that 2nd gear should slide off and be replaceable.