So the stock transmission in my c5 seems to be on its last leg, It will NOT stay in reverse without holding it and sometimes falls out of 1st, 6th grinds regularly and every now and then 3rd will grind. I have a Kirban shifter on the trans now which helped keeping it in 1st and reverse some, but was just a band-aid.

I have a few options do I pull the current trans and rebuild? If I do this what are the usual upgraded parts installed? When I do this I will be replacing the Clutch as well what is a good street clutch for this?

I also have located a reasonably priced c5Z transmission with very low miles on it, is it going to be a pain with the closer ratios in 3-4 and will my economy be worse on the highway in 6th?

Either way I go with the transmission I will be pulling the engine and rebuilding it ( has 155K miles on all the stock parts BTW) with some 243/799 heads and LS6 intake with a Cam we designed that i have in my Tahoe and love it, basically a modified LS6 cam. So I will be adding about 50HP over the stock 355HP it is supposed to have. So I am basically looking for advice on which transmission route to go with the engine mods I plan to add and also the best clutch that drives nicely. I do not plan on having any more than 400-425 HP in this car ever so all I want is a nice running/ driving car, that the wife can also hop in and drive when we go on cross country trips.

Thanks for any advice/ help in advance

 

You are much better off to buy a low mileage used M12 than having yours rebuilt. With the 2.97 1st gear, you will feel faster also. On a side note, with that many miles on your car, you might want to replace the diff while you're that much into it. Good luck!

 

So the Zo6 Transmission would be a better starting point? I have been reading and some are saying the trans. from the base C5 would be better. I'm just trying to get the best option for my car.

 

The gear ratios are personal choice but you're better off buying a low mileage used rather than to rebuild yours. Much cheaper that way.

 

My 2000 6 speed has been nutorious for embarrassing grinding or popping out of reverse, have been told to check the reverse solenoid, possibly bent reverse fork etc. got pee-oed, tore it out. Stood it on end after removing differential,popped rear cover on transmission to expose reverse fork. Common problem is the nylon tabs fail on shift fork. Mine were broken. Can replace the fork or tabs only, but can upgrade to bronze ones from "the gearbox". Waiting for mine in the mail. Plan on backing up without pulling my hat down!

 

Is this a common problem with 1st as well? Because I can deal with the occasional grind when I fail at shifting, but the falling out of gear is what really makes me mad. Also on the Clutch side of things what are some of the better street clutches out there?

 

As far as clutches go, price is usually the deciding factor. If you have a relatively stock car, I would go with the ls6 clutch and flywheel- It's light, holds over 400 lbft of torque, and looked practically new coming out of my car after 50,000 miles. If you have an upgraded engine the LS7 clutch works for most, but if you're racing or making serious hp then a twin or triple clutch can't be beat.

 

I did further investigation and found that my reverse gear is chewed up a bit, ordered a new one, also reverse sinchro can be turned around. I have also found some info where some have machined off up to1/8 inch off of the reverse fork where the shift rod goes through and then shim the same amount to move the fork further to engage all the way. Will reasseble and check before reinstalling the rear cover and then decide if this is viable. Also the bronze shift fork inserts are available as a set for all shift forks. Seems if there is a problem with other gears or racing with hard shifts this could be a problem with other fork inserts giving way to failure. Replacing 1-6 requires a puller and some special tools

 

The tools aren't an issue We build Transmissions as well as engines so I have access to them all. Just looking to use what works best and isn't going to go bad again for some time.