4 replies to this topic

[GeraldTheMini]

I have a DAM4818 gearbox I'm going to rebuild, it's disassembled and I can't see any cracking around the 4 bolt holes on the web. Should I be thinking about getting hold a 5626? The car will have a lightly modified 998.

[nicklouse]

It will be fine.

[Spider]

I wouldn't bother with that case. While you can't see any cracking, I'm sure if you had it tested, you'd find it will have at least a crack starting from the bolt hole that's at 10 O'clock, unless it's a very low mileage case, in which case, it'll soon crack. I've never come across any that haven't been, even going back to the late 70's when they were 'new'.

[GeraldTheMini]

Thanks both. Could any one pin point the differences? Ie, can I use a 5626 casting and transfer all my parts over? Or am I better sourcing a complete box.

[Spider]

The 4818 would be about the weakest cast they ever made, the centre web is rather frail and particularly thin above the mainshaft bearing. On the other hand, the 5626 was the strongest, the web is thicker and is reinforced. They also deleted that bolt hole that many other cases crack from.

 

Here's a 4818 caught soon after it started cracking;-

 

 

 

This was another I had wedled & machined, but deleted the bolt hole, it cracked again anyway !
 

 

 

And for comparison, this is a 5265, you can see the reinforcing lump on top of the web - these were developed for the Metro Turbo, but used in all models from it's introduction;-

 

 

Just a word of caution here though, while the 5262 is lighyears ahead of all cases before it in this area they can still crack from the other bolt hole, so check what you are buying.