Z/28 Mod Thread

[j o n]

Originally Posted by Racer56

Since I could not do any of the work myself, I am curious how much the 5th / 6th gear conversion might cost? Sounds like the way to go, especially on road courses.

If you watch the 'Ring lap in the Z-28, he must shift to 6th and the RPM's definitely die!

Just call Bowler, RPM, RSG... whomever

RSG is in NY

[ronchev]

Originally Posted by Racer56

Since I could not do any of the work myself, I am curious how much the 5th / 6th gear conversion might cost? Sounds like the way to go, especially on road courses.

If you watch the 'Ring lap in the Z-28, he must shift to 6th and the RPM's definitely die!

The ring lap you can clearly see at that point of the run when he shifts into 5th that it stays into the rpm range and still pulling (gaining speed), IMO this is not the 5th gear ratio that made in into our production cars but closer to the .80 ratio the ZL1 had. If that ring lap had the .74 5th gear like our cars came with then I don't believe it would have gained speed like it did because it would have dropped the rpm low enough that the engine would have been well below peek power. I know this is just my opinion but you can go to any of the online trans ratio calculators and figure our tires sizes, max rpm and each gear ratio to find max speed per each gear but if you figure our overdrive ratio's into those calculators with our production ratios 5th/6th gears (.74/.50) that would have our cars theoretically running well over 300mph and we all now thats not going to happen... Try the same thing with the gen5 ZL1 ratio's of .80/.63 and you will see a much more realistic mph figure. If you look back to the early 1LE's 3rd gens they made this very same change to the 5th gear going to a .80 ratio from a .74
because the teams that were road racing these cars were hollering about the rpm drop going into 5th gear so GM added it to these cars when ordered. There were also magazine's that covered this change back then.

As far as cost to do this change, I did get a few labor quotes but they were all over the place depending on who you called....as low as $250 all the way up to 2k plus parts.. and these were from some of the well known manual experts on line that we all can find, plus $250 plus to ship the trans somewhere, thats when I decided to just go for it and start rounding tools etc up. Price gets up there to high you may as well just get a new MG9 trans for a ZL1 and with a discount last I looked they were about 3200.... Hope this helps and good luck

[ronchev]

Originally Posted by j o n

Just call Bowler, RPM, RSG... whomever

RSG is in NY

Im only an hour away from RPM and figured this was easy for me but after several attempts with these guys I found out they didn't want to talk to me unless I was buying one of there upgrades packages with just an exchange trans, would not sell me parts ect... I did not want to give up my trans.. They seem to have a known good reputation but I didn't have much luck with them, may not be the case with others IDK.

Rockland Standard Gear was happy to sell me tremec parts at a far price and ship them in a timely matter.