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90 rear crossmember replacement

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This is how to replace the rear crossmember on any 90 - except the TD5 (which is made out of bean tins :) )

The replacement item is a crossmember with extensions (not a 1/4 chassis), and was bought from Bearmach. There were a few problems with fitting it and this is shown and explained in the thread as it occurs.

The usual corrosion problems. The rear face had already been plated before, but as usual - the rust had continued to spread.

Disconnect the battery.



The tow point, etc has already been removed, which makes things a lot easier. Just the tie-down rings to remove (17mm nut and bolt)


The rear section of exhaust has to be removed, so two 17mm nuts to remove to seperate the flange, then two mounts either side (13mm nut/bolt) - one on the top of the chassis rail on the drivers side, and one on a bracket on the rear crossmember on the passenger side.





There are 10 nuts/bolts (13mm) that hold the rear tub to the crossmember - remove 8 and leave one either side for now.


I cut the wiring loom and then solder it afterwards. You can disconnect it all from the rear lights and feed the wiring inside the chassis rail, or alternatively, pull the whole loom out of the rail and then cable tie it to the top of the chassis rail afterwards. I cut each wire about an inch from the next one so that when they are joined again it doesn't make a fat lump in the loom.


Remove the wiring from the clips where it crosses over to the passenger side and then cable tie it all out of the way.


Remove the plastic grommet from the crossmember.


And also the rubber grommet from the inside of the chassis rail where the loom comes out. Tuck the wiring inside the rail.

Chassis grommet on the right.


The new crossmember is designed to slot over the cut chassis rail - note that there is no inner tab. This is because it would interfere with the second floor support bracket, so a plate will have to be added afterwards.



This is the point where the old chassis rails should fit. Unfortunately it doesn't quite work like that - the tabs are too long on the top, so they have to be cut back - both to fit on and to be able to weld in the gap you have available with the tub still on the vehicle.


Carefully measure the point at which you will cut through the chassis rail - check, and double check you have got it right, then score the cut line - both inside and out of each rail. The tabs on the new crossmember wil overlap quite a bit, so it doesn't have to be that critical, but a close fit is always the best.



Then - using a plasma blade or ordinary 3mm cutting blade - cut the bottom, sides, and finally the top. Undo the two remaining 13mm bolts and the old crossmember will come away (keep an eye on the wiring loom as you do it)


The rot usually extends beyond the cut, and it's quite normal for there to be additional repairs to the chassis rails.

The new crossmember will be fitted and then repair plates added afterwards.




Overlap area cleaned off - wire brush in an angle grinder, then a flap wheel.



The new crossmember is a poor fit on the chassis - the depth is different, so there will be a step where the two meet. The top of the new crossmember had to be almost completely cut off, and the sides had to be reduced by 40mm. Even after this - the fit is still bad. Slide the new crossmember on and replace the 10 x bolts that hold it to the rear tub - don't forget to feed the wiring back through the hole.



Best of a bad fit really.



I tried to align the top as best as possible, but there's still a faint step. I welded along the top first, then the sides, added a plate to the bottom to smooth out the step, and then a plate on the inside of the rail to join the new crossmember to the chassis rail and repair the additional rust.




Not a very tidy job, but mis-alignment of the crossmember can sometimes make this very difficult.

Replace the two grommets and re-connect the wiring loom, replace the tie-down eyes, then coat the crossmember and rear of chassis with whatever you prefer. The exhaust mounting on the drivers side chassis rail was out of line, so the bracket that side will most likely knock. There's very little room there, so it looks like the silencer and/or bracket will have to be bent to prevent this.

As a comparison - the Bearmach crossmember was easier to fit in comparison to a Britpart item I recently fitted to a 110. Attachment to the rails was very messy - hence the apparent poor quality of welding and the join I had to create.

I've still not yet found a crossmember that fits as it should do - I guess measuring something the smae as what it will be replacing is more difficult than it seems! :(

Not such a good thread, but altering something to fit can be awkward and make the job look a bit crappy :(


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