GTO Gear Ratio's - Page 3

Eric Animal · 04-05-2008, 12:41 PM

TryRandy's Ring & Pinion click on the calculator section and enter values.....lot's of fun and info. Eric

Priest · 04-15-2008, 09:04 AM

When my dads GTO was a monster,
It had a 4.88 rear end

Rukee · 04-15-2008, 09:19 AM

Quote:

Originally Posted by Priest

When my dads GTO was a monster,
It had a 4.88 rear end

You mean a 3.08? Or a 3.90? I`ve never seen anything higher then a 4.56 ratio fit a std GTO rear end, and that thing would be screaming just running around in town with 4.88s, it would never be able to go down the highway without an overdrive unit unless it had just incredibly huge tall tires or somethin. Not to mention no-one I can find offers a 4.88.

Priest · 04-17-2008, 09:24 PM

Yup, Im sure my dad had a 4.88 haha

But yes, he did say it was a bad idea since the RPM red-lined and drove him crazy.
Hence why it was removed quickly.

BTW what does "std" stand for...referring to a GTO rearends lol

Rukee · 04-17-2008, 09:59 PM

std = standard
I`ve never seen a 4.88 fit a standard GTO rear end housing.

geeteeohguy · 04-18-2008, 01:32 PM

The only 4.88 geared GTO I experienced personally was my friend's '66. He put the gears in a 12 bolt unit we got out of a red 1970 455 4 spd GTO that we paid $175 for. (the ign. points had closed up). He tweaked the dwell and drove it home. We proceeded to strip the car and use the parts to re-do his '66. Back then (1980) we had NO idea that the '70 was extremely rare (something like 108 455HO 4 spd cars made total), or we wouldn't have parted it out. It was red with a parchment interior, and was pretty clean. I have never seen anything steeper than a 4.11 gear in a stock, early A body 10 bolt housing/carrier, though the Ram Air 1 in 1967 had a 4.33 gear standard in it's 10 bolt rear end.
Jeff

Priest · 04-18-2008, 09:28 PM

Sorry all, had a brain-fart resulting in the unrocognization of 'std'.

Any way that is because it wasnt in a standard GTO rear end.
The rear end was probably out of an A-body that could bolt right in.

70455goat · 04-23-2008, 03:16 AM

I am very interested in finding out what my rear end is.

UltimateGTO.com says my 70 (455) with a 12 bolt should have 3.07 (std) or 3.31 (opt). My GTO is completely all original and all I know is that it is pretty low geared. When I get on the freeway, it seems like I am still in second gear when I get up to 55-60 MPH. Correct me if I'm wrong, but 3.31 is not very low gears are they?

I couldn't find my source, but I remember reading info about a tag or something I should be able to find on the outside of my rear end. Does anyone know anything about it?

Dale,

Rukee · 04-23-2008, 07:59 AM

The cover on the back may have a tag. If you remove the cover there should be a # on the outside edge of the ring gear that will give the ratio. Or you could count the # of teeth in both the ring gear and the pinion and divide the pinion by the ring gear.
Or like I suggested above, jack up the rear end off the ground, turn the tires over one full revolution (if it`s a posi unit) and count the # of times the drive shaft turns over and that`s your ratio. If you have a 3.31 then the drive shaft will turn over 3 and almost a half revolutions for every time the tire turn over once.

ppurfield001 · 04-23-2008, 08:28 AM

Quote:

Originally Posted by Rukee

The cover on the back may have a tag. If you remove the cover there should be a # on the outside edge of the ring gear that will give the ratio. Or you could count the # of teeth in both the ring gear and the pinion and divide the pinion by the ring gear.
Or like I suggested above, jack up the rear end off the ground, turn the tires over one full revolution (if it`s a posi unit) and count the # of times the drive shaft turns over and that`s your ratio. If you have a 3.31 then the drive shaft will turn over 3 and almost a half revolutions for every time the tire turn over once.

Rukee's simple methodology above worked for me in determining that I had a 3.90 gear ratio.