I am about to do this mod because after the rebuild I've had three random pop-outs. I know all internal pieces are good, my builder showed me, so I am fitting detent as preventative measure. Clearly my builder got tolerances slightly off.

I found this statement from one of the UK rebuilders.

Does it sound right or is it BS as he wants to drum up his rebuild business?

This is what he says:

"Just a note on that detent... it makes the gear selector over throw the gear into all gears not just 2nd gear.. this is not the correct way to modify these gearboxes as now you have 5 other gears that are not at their correct engagement point. They are being overthrown onto the dogring and this can damage the teeth and sliding sleeve as it crashes down onto the gear! We have seen similar things and found 3rd/4th dog teeth rings with pieces broken off. If you want it done correctly you need to modify the gearbox internally".

Damn! Tanx.

 

I don't have an answer, but my gearbox is about to be sent to Eric, at GBox so interested in his response. I do have a lot of confidence in Eric as he seems remarkably knowledgeable about all these related to Porsche transmissions.

 

i concur on eric@gbox and his helpfulness and willingness to share his knowledge. i am not convinced however, that the gbox detent can really help once the damage to the dogring on second gear has become manifest. again, GL with it.

 

Sounds like your builder did a lousy job rebuilding your gearbox. I would get your money back and probably take what he has to say with a grain of salt. I had the Gbox detent added to my gearbox (which never had any pop out issues) and I can not tell any difference in feel.

 

My builder and the quoted builder are not the same. As I understand if you are not aware of the problem this is easy mistake to make when rebuilding. I guess this is where my builder went wrong. What I don't understand is that all my builder changed was the main shaft bearing and 1-3 snychros. He used my old shims so how could the tolerances change?

Anyway as I know all my internals are not damaged (yet) I hope gbox detent will work in my case. However what this uk builder is saying concerns me? Can someone who understand gbox detent and how it works chime in and agree or disagree with the quoted uk builder whereby detent endangers 3/4 gears.

 

[QUOTE=Terminator;3678643all my builder changed was the main shaft bearing and 1-3 snychros. He used my old shims so how could the tolerances change? [/QUOTE]

therein lies the problem. replacing the shims to the original oem spec and tolerances merely re-creates the intolerance that contributed to the problem occurring in the first place.

that is why Porsche recommended different ( from original ) shims when rebuilding the trans to remedy this issue ( once THEY figured this out ). this as explained to me by a factory tech and from their material ( updated ) which i was able to view.

unless folks have extensive experience with the 996t trans, the prescribed fix would simply be to rebuild to original factory spec. sounds like what has happened to you.

eg you have new parts with the same inherent weakness the trans had from the start.

 

I noticed a bunch of random pop-outs so i fitted the gbox detent 18 months ago. IT. NEVER. HAPPENED. AGAIN.

I know that they say once the damage is done you need a rebuild, but I figured it was cheaper to try this than to have my trans inspected.

2ndgear engagement now has a VERY solid/mechanical feel to it. The only downside is that I never hurry the shift and combined with the SSK, makes rapid 1-2 shifting require a certain degree of skill.

But thats what PDK is for right? (lols)

 

on balance, i would've tried the gbox detent too, had i not learned all this crap on porsche's dime. thankfully. two rebuilds for reasons cited above. cpo was worth every dime for this issue alone.

 

Maybe I didn't make myself clear. I had no pop-out issue prior to rebuild. So my question is if you change the main shaft bearing, fit 1-3 new synchros, reuse my original shims (no pop-out issue with them before) how can you **** up the rebuild. Gearbox works great apart from pop out (which only happened three times) since the rebuild.

 

I hope this fixes my problem too. I also have a quick shifter, did you notice any engagement differences apart from 1-2? How are other gears? Also, are you saying 1-2 are now more difficult to execute than before? Can you elaborate on this please...

 

perhaps i misunderstood, as well. i possibly assumed that was why you had a rebuild, which is what happened to me. i had 2nd gear popout and they RE-built the propensity toward the problem into my FIRST trans rebuild... and it began to occur within a few thousand miles after rebuilding it to ORIGINAL factory spec, as i've said. they corrected it on the second rebuild. what a PITA it was too.

i certainly can't tell you why you have the issue NOW while not having had it prior to rebuilding it, so back to square one, i'm afraid. i only know that porsche knows that it wasn't "quite" right the first time around, hence their recommendations to reshim the gear stack placement on LATER rebuilds.

i feel your pain man.

 

Could be as simple as tension on your shift cables after reinstall, combined with the facts that the shimming is mega sensitive. If the synchro ring tolerances are slightly different than what you had, it could be enough.

Do NOT drive the car anymore until you try the detent. The more popouts you get, the bigger the risk that it will not help with a detent anymore. Well, you can drive it but make sure to ALWAYS hold the gear in 2nd gear when slowing down.

Every time the gear slips out, it rounds a segment of dogs. The more it happens the more dogs get rounded, until you get a lot more pop-outs.

 

I had the fluid changed in my trans recently and the drain plug was covered with metal bits. I'm having the engine/trans pulled in order to have the trans sent to GBox. I don't want to risk grenading a 12-18K transmission. On the other hand, I knew going into it that this was a cost that I would need to incur at some point, so it was taken into consideration in the purchase price of the vehicle. Eric tells me that it will be better than new when it's done!

 

are you doing that pro-actively? or does your car have the dreaded issue? if not, that is some serious preventative maintenance. wow.

 

My own transmission popped out of second gear exactly 3 times in just over 3 years of ownership. After buying and sitting on the GBox second gear detent for over a year, my buddy helped me to install it (not exactly easy, but do-able if you're mechanically inclined).

Once the detent was installed, I have had 0 pop-outs, even when putting it under heavy decelerative force when going downhill...conditions that would have easily led to the pop-out condition before. The GBox detent has corrected my problem to this point. I don't really even notice the difference in the shift throw, but supposedly it travels a bit further in second gear (not enough that I can remember any difference anymore). Best wishes!