i was talking to a local proformance shop owner who specializes in setting up rearends, i was asking him about setting up my 10 bolt with 3.73 or 4.10 ring and pinion gears on my 95 z-28. He said he'd be glad to do it but he warned me that my car wouldn't pass the mass. emissions tests and it would fail after the mod. Is this true?

i realize that by increasing the overall drive ratio u will raise the rpm level at a given speed that my gas milage would go down but i didn't think it would effect anything with emissions. this this true?

 

That's one of the craziest things I've ever heard. Naw man, it won't efect your emissions in any way.

 

The only way I could see failing is being on the rollers and the people running the test falling it. There is are laws that say a speedo has to be within 3% but there are also laws orp Y pipes but anyone can buy them for off road use.

 

cool. The only thing that i could think of was mabye the guy is used to putting gears in older cars with 4 speeds or less so when they go for emissions testing their "highway cruise speed" puts out more emissions simply because they engine is reving much higher than it was before thus more exaust????? but anyway thats good to hear.

Also i have a 95 z-28 m6 and was planning in putting a set of gears in the stock 10-bolt rearend. i know that even if i put in 4.10's i'll still be fine on the highway but i'm unsure about whether or not i'll hook up with any traction with street tires (in my case bf goodrich g-force t/a's...(i think)...). Mabye 3.73's would be a better choice???

 

if you want to go 4.10s, use 4.11s actually
they are 9 ring 37 pinion and are a lot stronger than any other gear design just because they are different in the amount of teeth on each (like 4.10s have 10ring 40pinion, etc.)
i'm not sure you'd feel much of a difference w/3.73s personally

also, if you're going to run a power adder (i.e. nitrous, forced induction) you might want to keep those 3.42s in there