lefrog

It looks like my 3/4 shift fork is bent on my MN12. At my last hillclimb, I had a small grind getting into 3rd gear so I readjusted the shifter box as I thought it got misaligned. Everything seemed to shift fine after the realignment in the paddock. On the next run, I got stuck in 4th gear at the end of the straight but was able to negotiate the turns and stop the car without crashing. It took a minute or so before I was able to disengage the gearbox out of 4th. 1/2, 5/6 and reverse **** fine but if I engage in 3rd or 4th, it is really hard and it stays stuck in gear.
I guess this is at least a bent shift fork (02 Z06 with 33k miles, only 1.5K of racing). That would have to be replaced with a steel one like 03 and after.

If I'm going to go with a transmission overall, what other things should I do while I'm at it? Do you have a shop to recommend (I am in MA)?
Would it be cheaper to drop another transmission or upgrade to something else?

JeremyGSU

I went with a Level 5 RPM transmission T56. It comes with beefed up internals. Go to their website and check out them out. They are good transmissions and a lot of people use them.

JLZ06TR

Im in a similar predicament. From what I've seen, its a bit cheaper to have it rebuilt, unless you sell yours to recoup. Ive seen several people listing damaged trans for around 600-750, but I dont know if they ended up selling. A rebuild is around $1500, but a used trans usually runs around $2000-2500

0Anthony @ LGMotorsports

I would second the RPM Trans as well. We have been using them for years with no issues.


From the sounds of it, I think you probably bent one of the keys in the syncro's. Typically if it gets stuck in gear or locked out of a gear one or more of those keys have bent and is not allowing the syncro to move into or out of that gear.

Needs to have billet keys and new fork pads for sure...but easiest just to do a core sway for a unit already built.

Bluefire

with a Level 5 MN12 from RPM Transmissions. I converted my A4 to one of these Level 5's in last January. It's been rock solid on the track.

SouthernSon

After running an mm6 in my z I decided to go back to the 12 since I have an aggressive camshaft. I had it rebuilt by Rockland Gear. They are not cheap but it is a solid race ready prepared tranzila tranny. It has done well. Nothing wrong with the mm6 if you are interested.

Vettechris996

Sounds like it could be syncro keys. My 02Z got stuck in 4th and I wound up breaking all for stock keys.

I'm in MA and sent mine to RKT56 for a full rebuild and upgrade. Rick did awesome work and was great to work with and stands behind his work 100%. Getting it there and back was fairly easy. I shipped it freight via A Duie Pyle. Dropped it off and picked it up at on of their shipping hubs, super easy. Let me know if I can offer any more info or help!

Rick@RKT Performance

3-4 shift forks don't bend, they break. You most likely have broken synchronizer keys like these.

stevensa

I highly recommend rpm transmissions, they have a great reputations and provide an excellent product along with outstanding customer service.

SouthernSon

Good to hear about their outstanding customer service. A fellow at the NCM MSP today just lost 3rd gear sychros in his RPM prepped tranny that was installed last month. Even if RPM repairs it the way it should be for no cost this time, he is still out close to $1K for removal and reinstall with alignment.

lefrog

You are not the first one to report issues with RPM transmissions. I have already heard similar stories.
I think I will go with a rebuild and will be contacting Rick. Right now the Vette is parked for the rest of the season and I'm focusing on getting the STI logbooked for the upcoming rallysprint. This will most likely be a winter project now!

Thanks all for your advice and suggestions

SouthernSon

I certainly don't want to make unfair disparaging remarks about any particular company but this is information of which the members of CF need to be aware. The only reason the fellow went with RPM is because he was able to get it a lot quicker for an upcoming race. I guess there is a reason some of the others companies take a little longer for the turn around; they are busy, maybe a little more expensive but worth it.

Z06Tracker

A friend of mine and I both have had very good experiences with Tick Performance in Mount Airy, NC.

fatbillybob

These gearboxes look easy to rebuild and gears pretty cheap. Some pros are promoting deletion of the GM paper blocker rings for "carbon" blocker rings. Do the carbon ones work better? Do they work with the same dex3 spec or something else?