4x4 needs identical ratios front and back, and I believe the GMC had other than 3.90 in 59, confirm ratio first .... also might investigate if the 'funny noise' isn't just that it needs pinion bearing and resetting

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot