What type of rear axl? (Changing gears.)

[Jonas_N]

With some turning of the wheel I got my rear gear to 3.23.
I want to change to 3.55.
I have a 8 3/4, suregrip with 489 housing.

In this text:
1-7/8" tapered stem pinion (aka. '489')
Carrier casting numbers: 2881488, 2881489 (1969-1974). This assembly was introduced in 1969 and was phased-in to replace the 1-3/4" unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Pinion depth is set with shims, preload is set with a crush sleeve. Differential bearing setting (ie. backlash ) is set with threaded adjusters.

...it says the the 1-3/4 pinion appeared in some 489 carriers.

Can I find info about if I have the 1-7/8 or 1-3/4 pinion without taking the housing apart?
Thanks.

[fy469rtse]

Jonas,
never have i seen mixed pinions in two different housings. 742 to 489
but to be sure, if you have the tools, undo pinion nut , remove yoke and remove the front yoke seal,
outer bearing should come out and you should be able to see what is considered the weak point on a 489 case 8 3/4 centre,
to set pinion load they have a crush sleeve once pinion depth is set,
elimates the need to shim and re check,
i would look for the solid kit sleeve to replace this, but you should be able to see the sleeve, it will have bulged out roughly in the middle of sleeve, and the 742 solid shaft does not have a sleeve
if you have this it confirms what size your pinion shaft size is,
let us know how you go 

[Jonas_N]

Thanks for the tip. 
Thinking of buying a whole new kit and restore at the same time as changing gears.

[fy469rtse]

When you buy kit , buy extra shims for pinion depth,
Take note of shim thicknesses when you pull it apart, putting the same shim thickness back on new pinion will get yousome where near correct,
Read your service manual on this until it makes sense, torque wrenches a must, especially inch pound for pinion preload,
Good friend of mine showed me the correct way, done a few since and getting better at it , that solid sleeve will be more forgiving as they are 1 use only

[Jonas_N]

Thanks, will do.
As this will be my first rear axle restore I will study a lot before taking a tool in my hand.

[John_Kunkel]

"This assembly was introduced in 1969". Actually, the 489 was introduced in late '68.

[c00nhunterjoe]

I dont see how its possible to interchange pinions between 489's and 742's. Although i have never tried. The ring gears may swap but ivenever tried that either.

[fy469rtse]

742 489 pinion shaft size,
different bearing internal dimensions ,is the race outer the same size ?, never tried