We have a 1970 GMC 3/4T 4x4 350/4 sp /4WD (SM465 / NP205) with front lockout hubs and we are having driveline issues (as well as engine issues, but I want to address the driveline stuff first:
This truck lived its life as a construction truck and apparently had a flatbed on it for a large portion of the time, as it has weld spatter all over the roof and back window.
We have been working on this thing, getting it back into driving condition and have done the following:
NEW GM Crate 350 to match the stock factory 350
Rebuilt the SM465 4 speed (granny low transmission)
Rebuilt the transfer case (New Process NP 205)
Rebuilt the rear axle with new gears (4.11:1) and a new Detroit Locker, Dana 60
Rebuilt the front axle with new seals, Dana 44
Rebuilt front and rear driveshafts with all new yokes and U-Joints. (Inland Truck Parts)
Installed a Skyjacker 4" lift all-spring lift.
The original suspension had broken leaves in it and had a set of bolted-on overload springs on top of the original rear springs. This truck has had a lifetime of serious abuse. There is crap welded to it EVERYWHERE and we are trying to eliminate it as we can find it and get to it.
It apparently had a snow plow on it at some point.
We cut off about 150 LB of channel iron crap welded on the rear as a hitch. We left the 4" sch. 40 pipe bumper at this time.
Driveline issues:
When we first installed the lift, we reinstalled the original spacer blocks in the orientation that we took them out (doesn't mean it was right to begin with) and the thick side was to the REAR.
Skyjacker instructions instructed to place the thick part of the spacer on the spring pack to the REAR of the truck, consistent to what we started with.
Once all installed, the pinion was pointing UP in a "broke-back" configuration to the output shaft of the transfer case. It was giving weird axle-wrap issues and the clutch would not allow a smooth start, apparently due to axle-wrap.
We dropped the rear axle and turned around ALL the blocks and the pinion appears to be in correct alignment with the output of the transfer case (as in parallel).
We are now getting a vibration / bearing noise at the point of going from acceleration to deceleration. Possibly at the transfer case output.
So, we thought that MAYBE we were jamming the rear DS into the TC. So we measured the DS length at ride height, and full droop, and at deep compression.
I was surprised to see that at full droop the DS was SHORTER by 9/16" than at ride height.
When we compressed the rear (Added a LOT of weight in the bed), the DS never got longer than at the ride height. The splines were NOT protruding out the back of the yoke or anything.
This just seems backwards to me.
What driveline calculators do you all use and how do you confirm it is CORRECT?
Please help me with you experiences. I am calling a couple of you to this thread due to what I have read about you doing to your 80's, and I greatly respect that.
@nukegoat @jcardona1 @Tools R Us @inkpot
If you can't help or don't want to get into this, that's OK too. I appreciate your time.
This truck lived its life as a construction truck and apparently had a flatbed on it for a large portion of the time, as it has weld spatter all over the roof and back window.
We have been working on this thing, getting it back into driving condition and have done the following:
NEW GM Crate 350 to match the stock factory 350
Rebuilt the SM465 4 speed (granny low transmission)
Rebuilt the transfer case (New Process NP 205)
Rebuilt the rear axle with new gears (4.11:1) and a new Detroit Locker, Dana 60
Rebuilt the front axle with new seals, Dana 44
Rebuilt front and rear driveshafts with all new yokes and U-Joints. (Inland Truck Parts)
Installed a Skyjacker 4" lift all-spring lift.
The original suspension had broken leaves in it and had a set of bolted-on overload springs on top of the original rear springs. This truck has had a lifetime of serious abuse. There is crap welded to it EVERYWHERE and we are trying to eliminate it as we can find it and get to it.
It apparently had a snow plow on it at some point.
We cut off about 150 LB of channel iron crap welded on the rear as a hitch. We left the 4" sch. 40 pipe bumper at this time.
Driveline issues:
When we first installed the lift, we reinstalled the original spacer blocks in the orientation that we took them out (doesn't mean it was right to begin with) and the thick side was to the REAR.
Skyjacker instructions instructed to place the thick part of the spacer on the spring pack to the REAR of the truck, consistent to what we started with.
Once all installed, the pinion was pointing UP in a "broke-back" configuration to the output shaft of the transfer case. It was giving weird axle-wrap issues and the clutch would not allow a smooth start, apparently due to axle-wrap.
We dropped the rear axle and turned around ALL the blocks and the pinion appears to be in correct alignment with the output of the transfer case (as in parallel).
We are now getting a vibration / bearing noise at the point of going from acceleration to deceleration. Possibly at the transfer case output.
So, we thought that MAYBE we were jamming the rear DS into the TC. So we measured the DS length at ride height, and full droop, and at deep compression.
I was surprised to see that at full droop the DS was SHORTER by 9/16" than at ride height.
When we compressed the rear (Added a LOT of weight in the bed), the DS never got longer than at the ride height. The splines were NOT protruding out the back of the yoke or anything.
This just seems backwards to me.
What driveline calculators do you all use and how do you confirm it is CORRECT?
Please help me with you experiences. I am calling a couple of you to this thread due to what I have read about you doing to your 80's, and I greatly respect that.
@nukegoat @jcardona1 @Tools R Us @inkpot
If you can't help or don't want to get into this, that's OK too. I appreciate your time.