Hi guys,
So, I've been chasing a gremlin in my drivetrain for sometime now. Quick sum-up:
1A. The truck developed a roar/vibration on the highway. I had been driving at around 70mph for 50 miles, and began to smell gear oil. I hopped out, but didn't see a leak. Within another 20 miles I had a very bad roar/vibration that started around 35mph and got much worse from there.
1B. The noise occurs in RWD, not FWD. It occurs under load/acceleration only (not during deceleration in gear, not with the clutch in while in gear, not in neutral).
2. Bronco-specific mechanic in Venice said it was my transmission (which didn't make sense to me). To note - he installed a new Truetrac within 200 miles of the problem beginning, but insisted the noise was not coming from the rear end.
3. I then had the driveshaft rebuilt, and the heavy duty Output Shaft components from WH/Advance Adapters rebuilt by AA. No change.
4. I wanted to swap in a 5spd anyway, and thanks to Covid, suddenly had the time to do it myself, so I completed the NV4500 swap. This included redoing both driveshafts... again. Noise is STILL THERE.
5. I took the truck to a rear end specialist. He said the driveshaft angle was too steep, and that if I corrected that, it would solve the problem. This also didn't jive with the way the problem developed in my mind, since the noise appeared after a period of driving. I could see it being the driveline angle AND a worn out <insert worn out part>.
6. I (temporarily) lowered the transmission cross member one bolt hole, which equaled around 1-1.5". This took the driveshaft angle from 20deg to 16deg. No effect.
7. I called my driveshaft shop to see what they thought about the angles. They mentioned either 20deg or 16deg would be "fine, but 16deg is better, of course." He mentioned that, perhaps, the pinion yoke had been warped as a result of a stripped u-bolt on the driveshaft, which I had initially when I went to take off the driveshaft the first time.
8. Today, I changed the pinion yoke. No effect.
Below are links to two videos. I uploaded them to YouTube because I can't get them to upload on the forum directly... either too big or the wrong format, or both.
The first (floor installed) is driving from start through about 40mph with the ol NP435 installed. I start the truck in second, and you can hear the noise begin at the end of third, and heavily in 4th.
https://youtu.be/TaxLhLXbix0
The second (floor uninstalled) is driving at slow speed with the NV4500. There is a noise that you can hear distinctly around the 20sec mark.
https://youtu.be/FUU09u9jgyc
So - any ideas? I'm stumped.
So, I've been chasing a gremlin in my drivetrain for sometime now. Quick sum-up:
1A. The truck developed a roar/vibration on the highway. I had been driving at around 70mph for 50 miles, and began to smell gear oil. I hopped out, but didn't see a leak. Within another 20 miles I had a very bad roar/vibration that started around 35mph and got much worse from there.
1B. The noise occurs in RWD, not FWD. It occurs under load/acceleration only (not during deceleration in gear, not with the clutch in while in gear, not in neutral).
2. Bronco-specific mechanic in Venice said it was my transmission (which didn't make sense to me). To note - he installed a new Truetrac within 200 miles of the problem beginning, but insisted the noise was not coming from the rear end.
3. I then had the driveshaft rebuilt, and the heavy duty Output Shaft components from WH/Advance Adapters rebuilt by AA. No change.
4. I wanted to swap in a 5spd anyway, and thanks to Covid, suddenly had the time to do it myself, so I completed the NV4500 swap. This included redoing both driveshafts... again. Noise is STILL THERE.
5. I took the truck to a rear end specialist. He said the driveshaft angle was too steep, and that if I corrected that, it would solve the problem. This also didn't jive with the way the problem developed in my mind, since the noise appeared after a period of driving. I could see it being the driveline angle AND a worn out <insert worn out part>.
6. I (temporarily) lowered the transmission cross member one bolt hole, which equaled around 1-1.5". This took the driveshaft angle from 20deg to 16deg. No effect.
7. I called my driveshaft shop to see what they thought about the angles. They mentioned either 20deg or 16deg would be "fine, but 16deg is better, of course." He mentioned that, perhaps, the pinion yoke had been warped as a result of a stripped u-bolt on the driveshaft, which I had initially when I went to take off the driveshaft the first time.
8. Today, I changed the pinion yoke. No effect.
Below are links to two videos. I uploaded them to YouTube because I can't get them to upload on the forum directly... either too big or the wrong format, or both.
The first (floor installed) is driving from start through about 40mph with the ol NP435 installed. I start the truck in second, and you can hear the noise begin at the end of third, and heavily in 4th.
https://youtu.be/TaxLhLXbix0
The second (floor uninstalled) is driving at slow speed with the NV4500. There is a noise that you can hear distinctly around the 20sec mark.
https://youtu.be/FUU09u9jgyc
So - any ideas? I'm stumped.
