Quote:
Originally Posted by 88Stanger
Please excuse my ignorance, but what is meant by narrow vs wide rearend?
PS thank you to all of you for these great responses.
|
The 'early' truck 12bolts changed width as disc brakes came along. At some point in '70, the rear ends started being made 1.5" wider vs. pre-'70. So, 63-69 rear ends were the narrow 12bolt. In 1970, as production started building things for the new '71 models (that would now have standard disc brakes up front), the housings were wider width but w/6-lug axles. Starting in '71, the axles changed to 5-lug.
Since these trucks are so old & parts are easily swapped between the years, you have to pay attention to what you have & not assume just because it's 'X' year model, it will work. From what I learned:
63-64 'narrow' 12-bolt 17-spline axles
65-69 'narrow' 12-bolt 31-spline axles
70 could be either the narrow or wider by 1.5" 12-bolt 31-spline axles
71-80 'wider' 12 bolt 31-spline axles
Any of the above from 63-72 could be truck-arm or leaf housings. The additional width was outboard of the T/A or leaf mounting pads.
81-87/91 'wider' 10 or 12 bolt
In 88, the C/K GMT400 style rear housings/axles got an increase in width again by 1.5".
So, if you have a truck that has one of the possible '70 model wider housings swapped in prior to your ownership, things are different vs. something that came as factory. A buddy & I learned this the hard way (after he spent $$ on new wheels).