I am converting a '03 Silverado to a T56 manual trans for a customer of mine. I heard the GTO T56 had stronger internals, slightly different gearing, a triple cone synchro's so I chose that over the F-body T56. Everything with the swap was going well until I tried to use an F-body shifter on the GTO trans. When I bolt up the F-body shifter, it will not shift into all the gears. I compared the two side by side, and they are different. I can't use the GTO shifter because it sits too far back and would interfere with my center console. SO, my question is there something internal that can be exchanged to use the F-body shifter or am I stuck with the GTO shifter?


Cody

 

I asked this question over at LS1tech and got almost an immediate answer.

Thanks again member: rollinna65

Here's what he said....

"All you've got to do is knock that little roll pin out of the shifter cup where its meets the shift rail and replace it with one from an fbody. The fbody one puts the shifter back up where you want it. If you don't have a spare shifter cup I think you can get a new one for $25-35."

So, my next question is where can I find an F-body shifter cup? Anyone here have a spare or the GM part number for that?

 

Lucky bastard. I've been trying to hunt down a M12 for a long time out of a GTO or caddy CTS-V. Where'd you find yours?

 

Thanks once again to Members: 85MikeTPI and rollinna65

Parts needed to put an F-body shifter on a GTO trans:
The Tremec number is:
Shifter offset lever 1386-098-016

I had to grab a spare from thegearbox for about $27

You'll probably need the bushing also, 1352-127-009

OR CALL.....
The only place I know of to get one, right off the top of my head, is six speeds inc but they're hard to get ahold of at the moment due to the hurricane. If you look through these threads you can find the owner's cell phone number and contact them.

Here's a thread that shows the differences between the fbody and gto shifter cup.

https://ls1tech.com/forums/showthrea...ht=cup+shifter

 

Well, I came home from my 2nd job one day to find a LS2/T56 combo with 14,000 miles from an '05 GTO sitting in my shop. My father was told about it from my neighbor and he acquired it from ????? My neighbor was just going to STORE (????) it in his garage until he found a use for it. You don't wanna know how much I got it for either or you will be VERY pissed! BTW I am located in NorthEast, Ohio.

 

Good info.
To change out the shifter cup assembly you will need the trans in a vertical position with input shaft down. You will either need a hole cut in a bench or it supported in some way in this position, if you don't the 5-6 gear assembly will fall out of the bearing cups when you remove the tail housing. You may not have to remove the housing the whole way but it will be easier to scrape the rtv and apply new. But before you remove the tail housing, take the two torx head screws out that hold the detent plate under the shifter cup. It has to slide out with it and be careful to not loose the detent ball when you pull the housing up.
Installing I have found that holding the detent spring and ball in with a tie wrap around it and then cut it once installed. It has to go together at the same time and an extra pair of hands is helpful but not necessary.

 

TurboGibbs, I am not sure how the GTO M12 trans differs from the F-body trans but I DID NOT have to do ANYTHING you stated above!!!!

What I did was.....
"All you've got to do is knock that little roll pin out of the shifter cup where its meets the shift rail and replace it with one from an fbody. The fbody one puts the shifter back up where you want it. If you don't have a spare shifter cup I think you can get a new one for $25-35."