Ian Barrett Posted March 25, 2011 Share Posted March 25, 2011 Hello chaps. During the renovations of my 1986 Ninety I've removed the rear tub to crossmember bolts remove the crossmember paint to find there is loads of ali oxidisation underneath There is nothing between the crossmember brackets and the tub so I'm guessing its either this or the bolts themselves causing the oxidisation. As the crossmember was replaced about 5 years ago I don't know if there should be something between the crossmember brackets and the tub or if its the bolts/washers/nuts themselves causing the problem. Can anyone offer any advice on how to cure this. Thanks guys IanB Quote Link to comment Share on other sites More sharing options...
Les Henson Posted March 25, 2011 Share Posted March 25, 2011 Originally there would have been double plates with welded nuts on the inside for the three central pairs and nuts and bolts for the outer 4. There is usually also shims between the tub and crossmember brackets. Electrolytic corrosion occurs where there is contact between steel and alloy, so either the bolts themselves and the tub, or the crossmember tabs and the tub. As a replacement crossmember is usually bolted to the tub in order to align it before welding - the shims are quite often no longer necessary/not fitted. The plates with the welded nuts on are also usually missing because they break or are badly corroded and are replaced with new nuts, bolts and washers. Les. Quote Link to comment Share on other sites More sharing options...
Ian Barrett Posted March 26, 2011 Author Share Posted March 26, 2011 Ah, that explains quite a bit Les, thanks. It looks like the new crossmember tabs weren't welded at the factory, so I'm guessing they put them onto the body then welded them on to ensure correct alignment. So it would make sense shims weren't used. I don't know if its possible but I might try to squeeze a bit of innertube between the body and the tabs, and make up some rubber washers for the backs too. Cheers Les, you've helped a lot. Ian Quote Link to comment Share on other sites More sharing options...
mrtod Posted March 27, 2011 Share Posted March 27, 2011 Ah, that explains quite a bit Les, thanks. It looks like the new crossmember tabs weren't welded at the factory, so I'm guessing they put them onto the body then welded them on to ensure correct alignment. So it would make sense shims weren't used. I don't know if its possible but I might try to squeeze a bit of innertube between the body and the tabs, and make up some rubber washers for the backs too. Cheers Les, you've helped a lot. Ian Hi - I used a margarine tub - http://projectd90.blogspot.com/2011/03/rear-cross-member-1001-uses-for.html - hope this helps:) Quote Link to comment Share on other sites More sharing options...
Ian Barrett Posted March 28, 2011 Author Share Posted March 28, 2011 bloody marvellous idea mrtod, and keep up the good work with the website - I had a good rummage about and found it all very interesting. Quote Link to comment Share on other sites More sharing options...
Litch Posted March 28, 2011 Share Posted March 28, 2011 I used sections of an ice-cream tub, just the job. Quote Link to comment Share on other sites More sharing options...
mrtod Posted March 28, 2011 Share Posted March 28, 2011 bloody marvellous idea mrtod, and keep up the good work with the website - I had a good rummage about and found it all very interesting. Thanks very much - all feedback is much appreciated:) Quote Link to comment Share on other sites More sharing options...
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