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View Full Version : 1b rear suspension bracket onto a 1a - will it fit



MartG
22-10-2007, 20:14
Due to my 1b shell dying of tinworm, I need to swap the uprated bits of the 1b suspension onto my 1a. Simplest way is to swap the whole lot over, but there is the issue of the differing rear suspension brackets - so I had a close look at the two shells...

The pic below shows the rear suspension bracket mounting area of my 1a. The 1a bracket attaches using bolt holes 1, 2, 3, and 7. The ARB fixes to holes 4 and 5 ( with a drain hole between them normally blocked by the ARB bush ), and 6 is one of the mounting holes for the exhaust heat shield.

It is difficult to see in this pic, but the crossmember actually curves slightly forwards toward its outer ends.

http://img230.imageshack.us/img230/173/1aholesrj6.jpg (http://imageshack.us)

Here we have a pic of the same area of my 1b - an important difference is that the front face of the crossmember curves forwards exactly the same as the 1a one, but the rear face doesn't - it runs straight across.
The holes all have the same number as on the 1a pic above, but note that hole 3 is missing entirely, hole 4 is now used for the suspension bracket rather than the forward ARB bolt, and there is a new hole ( 8 ) for the aft ARB bolt, and as the drain hole is no longer covered by the ARB bush a blanking plug is fitted. Hole 7 is also further inboard and lower down.

http://img530.imageshack.us/img530/2418/1bholessf5.jpg (http://imageshack.us)

Conclusions - to use the 1b rear suspension on the 1a chassis needs a new aft ARB mount bolthole to be drilled, a new transverse hole ( 7 ) to be drilled and spacing washers use to fill the gap where the 1a crossmember curves forwards ( and the 1a captive nut to be ground off and replaced )

Simple innit :thumleft:

OlberJ
22-10-2007, 20:37
Bloody good work sir :clap:

snowtigger
22-10-2007, 22:36
all sounds a bit nuts to me

lodgeman
22-10-2007, 22:41
do you think it will alter the geometry at all? good work though!!:thumbsup:

shummy002
11-04-2009, 16:47
I am in the middle of this swap and I have to say that it will work. Needs a bit more work then stated above but just a bit. On the Mk1a bolthole 4 is smaller then holes 2 and 3. The solution is simple: drill a new hole in the subframe for bolt 3. The outside is now held by 3 bolts instead of 2.

As for bolt 7: I'm going to take a piece of steel and wedge it on one side so that it sits flush with the chassis and the subframe. The bolt is offset just a bit so I might have to cut a corner of the subframe but we'll see. The wedged plate will be welded to the subframe so it will be plenty strong.

At first glance the alignment seems to be okay but I will know for sure when I get the otherside modified.

Before: Mk1b on the left, Mk1a on the right
http://www.twobrutal.co.uk/forum/images/recovered/2009/04/33.jpg

After
http://www.twobrutal.co.uk/forum/images/recovered/2009/04/34.jpg

Extention plate for bolt 7
http://www.twobrutal.co.uk/forum/images/recovered/2009/04/35.jpg

Cut a piece of the subframe to make room for the bolt and weld
http://www.twobrutal.co.uk/forum/images/recovered/2009/04/36.jpg

Then welded them together
http://www.twobrutal.co.uk/forum/images/recovered/2009/04/37.jpg

Finnished off with some underbodycoating to prevent rusting.

The reason I didn't want to drill extra holes in the chassis is that in the original holes there are pipes to prevent you from crushing the chassis member. It took me only about an houre to make the plates and weld them in place. Subframes are nice and solid now and the alignment is still very good ( still need to get a 4 wheel alignment but I'm not expecting any problems.