3.42's on a Y87 M5 - factory freak? (updated)

[zlexiss]

Base info: Car is a 2001 M5 Firebird with the Y87 package.

Changing out my differential fluid today, and was getting into things. I had seen some pics a fellow autocross/road racer posted of worn c-clips (I know, they're not _supposed_ to wear), and caught the stamps on the edge of the ring gear.

It clearly had 3.42 stamped on the edge of the gear after the part number. Wish I had my cam for a pic, or written the part number down. My door indicates GU5, which is 3.23 gears, which all M5 (Y87 or not) are supposed to have.

I wouldn't think the gear was mis-stamped, speedo has always seemed right, so I'm not sure where this thing lies between gearing and computer speedo comp.

Any thoughts?

-Jeff

[ July 21, 2004, 12:04 AM: Message edited by: zlexiss ]

['98 BlackBird]

hmmm.... thats very interesting. did you buy the car new or used? Could it have possibly been from a previous owner who had the rear gears fixed?

[zlexiss]

Brand new, built to order - they couldn't find anything with the option combo I wanted (power everything, M5, Y87, hardtop), so I had to wait a couple months for it.

-Jeff

['98 BlackBird]

yep, its factory freak. maybe you really do have 3.42 gears and they put a wrong sticker on your car.

[98goldbird]

Could be a F.F. By the way, why did you want a hard top?

[MustangEater8251]

Originally posted by zlexiss:
Brand new, built to order - they couldn't find anything with the option combo I wanted (power everything, M5, Y87, hardtop), so I had to wait a couple months for it.

-Jeff

yeah they were hard to fine...

My dad looked for awhile eh oculd only find fully optioned t-top cars with autos. or a striped car with 5-speed.

In the end he found my car, mildly optioned with 5-speed but a hardtop

[zlexiss]

Originally posted by 98goldbird:
By the way, why did you want a hard top?

Quieter, maybe a little stiffer/lighter, and with the Tucson sun and heat, I didn't want to care for a vert top or deal with the extra greenhouse effect of t-tops.

[camaroincal]

Hey I'm just curious what mph each gear (M5) tops out with the 3.42's

[zlexiss]

Update: looks like I have 3.23's after all.

After looking at the 4th Gen Tech Aides I saw a link to Find the Differential Gear Ratio (w/inspection cover off)

Looks like "3.42" was probably the "13-42" count for the gears, which equals the 3.23 set (GM stamps the pinion-ring teeth on the gear, not the ratio).

So, life is back to normal.

-Jeff

[RallyRed 98]

not sure why people see 13-42 stamped on their gears and think they have 3.42s... you definitely aren't the first

[AZ3.8Camaro]

When I did my gear swap the other day, I noticed the same thing... Got me thinking too, so I counted the teeth... [img]smile.gif[/img]

[ravenp]

Honest mistake... good to know what you REALLY have though eh? [img]smile.gif[/img]