302Rover
Member
Hello all in Roverland,
a few weeks ago I posted about the vibration problem I've been having in my P6 with the Ford V8. Since then I've done a lot of testing and fiddling but to little avail. Here is what was done and if anyone has any further suggestions, please comment.
1. Put the car up on blocks under the rear suspension and removed the wheels, half shafts, and brake rotors.
2. Started the car, put it in 5th gear and ran it up slowly to 80 mph (yeah, a bit dicey, I know). Vibration started at around 57 mph and stayed at a fairly steady level, annoying but not severe, right on up to 80.
3. Used a digital angle gauge to refine the driveline angles but that did nothing to improve the situation.
4. Noticed that the prop shaft angle in the horizontal plane was fairly severe so built an adapter to move the front diff mount 5/8 inch towards the center of the car, thus getting better prop shaft alignment at the expense of half shaft alignment. No improvement.
5. Removed two 1/8 inch thick washers from between the cast iron halves of the damper system at the front of the diff pinion extension housing and clamped down on the 3 rubber 'disks'. This helped, reducing the amplitude of the vibration and increasing its frequency. The vibration now starts at about 64 mph and stays more or less steady on up to 80. Above that I lost courage with the car up on blocks and the speedo reading 80 mph. If all else fails, this could be acceptable yet still annoying.
6. Removed the prop shaft and took it to the best driveline shop in town. Duane The Driveshaft Guy spun it up and said it was in pretty good balance but he could do some slight improvement by replacing the ujoints with Spicer 'permanent lube, cushioned' u joints and rebalance. After doing this, he told me it was balanced as well as it could be and the best that he has ever done. At least I eliminated prop shaft balance as a root cause. Still no change on the car, however.
7. I replaced the half shafts and ran the car up to speed on the blocks again. No change, which is good news, thereby eliminating the half shafts from the equation. And to be on the safe side, I also had the brake rotors balanced.
8. So what I seem to be left with is the diff itself, which was salvaged from a 3500S. I have been told and read that the pinion extension shaft is suspect and a weak point. I'm wondering if it could be slightly bent or distorted, causing an imbalance at high speeds. Has any one ever come across that problem? Duane The Driveshaft Guy also pointed at the extension shaft as a possible culprit.
9. Classeparts do offer an improved pinion extension shaft and rebuilding the diff using that shaft could be an option, albeit pricey.
10. Another option might be swapping in a Jag diff such as Simon Owen did with his muscle car project. I do have access to a diff from an XJS. But the Forum archive thread covering Simon's project seems to be missing all its photos that were posted on Photobucket. What's happened there?
Right now I am very frustrated so any bright ideas, blinding insight, random thoughts, or anything else that could become "The Straight Word from the Golden Trough" would be greatly appreciated 8)
Cheers,
Tom
a few weeks ago I posted about the vibration problem I've been having in my P6 with the Ford V8. Since then I've done a lot of testing and fiddling but to little avail. Here is what was done and if anyone has any further suggestions, please comment.
1. Put the car up on blocks under the rear suspension and removed the wheels, half shafts, and brake rotors.
2. Started the car, put it in 5th gear and ran it up slowly to 80 mph (yeah, a bit dicey, I know). Vibration started at around 57 mph and stayed at a fairly steady level, annoying but not severe, right on up to 80.
3. Used a digital angle gauge to refine the driveline angles but that did nothing to improve the situation.
4. Noticed that the prop shaft angle in the horizontal plane was fairly severe so built an adapter to move the front diff mount 5/8 inch towards the center of the car, thus getting better prop shaft alignment at the expense of half shaft alignment. No improvement.
5. Removed two 1/8 inch thick washers from between the cast iron halves of the damper system at the front of the diff pinion extension housing and clamped down on the 3 rubber 'disks'. This helped, reducing the amplitude of the vibration and increasing its frequency. The vibration now starts at about 64 mph and stays more or less steady on up to 80. Above that I lost courage with the car up on blocks and the speedo reading 80 mph. If all else fails, this could be acceptable yet still annoying.
6. Removed the prop shaft and took it to the best driveline shop in town. Duane The Driveshaft Guy spun it up and said it was in pretty good balance but he could do some slight improvement by replacing the ujoints with Spicer 'permanent lube, cushioned' u joints and rebalance. After doing this, he told me it was balanced as well as it could be and the best that he has ever done. At least I eliminated prop shaft balance as a root cause. Still no change on the car, however.
7. I replaced the half shafts and ran the car up to speed on the blocks again. No change, which is good news, thereby eliminating the half shafts from the equation. And to be on the safe side, I also had the brake rotors balanced.
8. So what I seem to be left with is the diff itself, which was salvaged from a 3500S. I have been told and read that the pinion extension shaft is suspect and a weak point. I'm wondering if it could be slightly bent or distorted, causing an imbalance at high speeds. Has any one ever come across that problem? Duane The Driveshaft Guy also pointed at the extension shaft as a possible culprit.
9. Classeparts do offer an improved pinion extension shaft and rebuilding the diff using that shaft could be an option, albeit pricey.
10. Another option might be swapping in a Jag diff such as Simon Owen did with his muscle car project. I do have access to a diff from an XJS. But the Forum archive thread covering Simon's project seems to be missing all its photos that were posted on Photobucket. What's happened there?
Right now I am very frustrated so any bright ideas, blinding insight, random thoughts, or anything else that could become "The Straight Word from the Golden Trough" would be greatly appreciated 8)
Cheers,
Tom