68z28 speedo gears

[sd1968z28]

   i just installed the original rear axle assembly back in my car, it has 4.88 gears and holy cow what a difference.  the speedo is now off by iwould guess 10 mph.  what do i need to fix this problem.  it has 302 original engine, m21 trans and E70 15 tires.  also the shifter seams to droan now, is this common for a low gear car?

[firstgenaddict]

The engine is running at a higher RPM now so you are just not used to the sound, it is normal in a car with steep gears, you will get used to it.
The speedo will be off a percentage... not a speciifc number.
You may be able to buy the trans gear at the Chev dealer... if not there are Stewart Warner gear reducers all the time on ebay...

[JohnZ]

I don't believe there was any factory combination of drive and driven gears that worked for a 4.88; you'll need an adapter gearbox made up. Try these guys:

http://www.gaugeguys.com/ratioadapt.htm

[sd1968z28]

i figured i would need a box, hopefully i an get one so i don't need to take the trans apart.  this is the factory srt up so i guess they used an reduction box also?

[JohnZ]

i figured i would need a box, hopefully i an get one so i don't need to take the trans apart.  this is the factory srt up so i guess they used an reduction box also?

The factory used a ratio gearbox on cars with 4.56 axles - it's shown with the drive "key" in the Assembly Manual in section G80, Sheet A2.

[sd1968z28]

thanks for the info.