So...
I'm swapping my Discovery 300Tdi's 3-bolt rear propshaft for a 4-bolt. However, on arrival, the balance weight on the 4-bolt prop looked like this:
Not great. Rust had got to it such that part of it was missing and the rest was flaky. I didn't want it coming away and causing a vibration that would trash my differential pinion seal and possibly bearings. If it needs it, I'll send it away for balancing, but I figured that I could probably achieve an acceptable level of out-of-balance simply by replacing what was there with good metal. So I marked and measured the old weight, and then prised and chiseled it away, catching it all in a plastic bag. No power tools - I didn't want to lose any of the rusty weight in the process.
Bag of rust, on scales:
I guestimated that that weight represented perhaps 90% of the original balance weight. Mild steel has a density of about 7800kg/m3. 1.5mm thick steel sheet delivered the required weight at close to the original 50mm x 40mm size of the old balance weight:
Then I needed a means of welding it to the shaft. I didn't want to add extra metal in the process, so I drilled some holes in it to plug weld through, before bending it to match the curvature of the shaft:
Then I welded it in and ground off any excess metal:
Finally it all got a coat of paint ready for fitting.
It won't be as well-balanced as a new shaft, but it should be as well-balanced as when it came into my possession, with the added benefit of being balanced with steel rather than rust and hence standing half a chance of holding together for a while without further deterioration.
I'm swapping my Discovery 300Tdi's 3-bolt rear propshaft for a 4-bolt. However, on arrival, the balance weight on the 4-bolt prop looked like this:
![Propshaft before.jpg Propshaft before.jpg](https://www.landyzone.co.uk/data/attachments/101/101352-863df46a8091c92c90f6b2c7052f63d4.jpg)
Not great. Rust had got to it such that part of it was missing and the rest was flaky. I didn't want it coming away and causing a vibration that would trash my differential pinion seal and possibly bearings. If it needs it, I'll send it away for balancing, but I figured that I could probably achieve an acceptable level of out-of-balance simply by replacing what was there with good metal. So I marked and measured the old weight, and then prised and chiseled it away, catching it all in a plastic bag. No power tools - I didn't want to lose any of the rusty weight in the process.
Bag of rust, on scales:
![Propshaft rust.jpg Propshaft rust.jpg](https://www.landyzone.co.uk/data/attachments/101/101353-e8576268497ad7504c8e35b26f51eb85.jpg)
![Propshaft weight.jpg Propshaft weight.jpg](https://www.landyzone.co.uk/data/attachments/101/101354-ca74d2d12a120e4d7965303d1688cd95.jpg)
I guestimated that that weight represented perhaps 90% of the original balance weight. Mild steel has a density of about 7800kg/m3. 1.5mm thick steel sheet delivered the required weight at close to the original 50mm x 40mm size of the old balance weight:
![Propshaft new weight.jpg Propshaft new weight.jpg](https://www.landyzone.co.uk/data/attachments/101/101355-8eb3410beb282ad92059d6cde21be277.jpg)
Then I needed a means of welding it to the shaft. I didn't want to add extra metal in the process, so I drilled some holes in it to plug weld through, before bending it to match the curvature of the shaft:
![Propshaft new weight drilled and shaped.jpg Propshaft new weight drilled and shaped.jpg](https://www.landyzone.co.uk/data/attachments/101/101356-a78bce1467b7646fcc6101e6413fddbe.jpg)
Then I welded it in and ground off any excess metal:
![Propshaft weight welded and ground.jpg Propshaft weight welded and ground.jpg](https://www.landyzone.co.uk/data/attachments/101/101357-0d3b98609920e9563cf84d8675f98b9b.jpg)
Finally it all got a coat of paint ready for fitting.
![Propshaft sprayed.jpg Propshaft sprayed.jpg](https://www.landyzone.co.uk/data/attachments/101/101358-fb2e47f3c1d619b00f08de218cb4fa4b.jpg)
It won't be as well-balanced as a new shaft, but it should be as well-balanced as when it came into my possession, with the added benefit of being balanced with steel rather than rust and hence standing half a chance of holding together for a while without further deterioration.