7 replies to this topic

[Mini Mad Drakeley]

Hi,

as said in title really,i have 2 pre A plus gearboxes from a 998 and a 1275, the 998 casing is broke in one corner as i stupidly left a bolt in and im wondering if the 1275 gearbox would be a straight swap or if much needs changed, looking at it, the 1275 casing seems slightly taller but i tried the 1275 engine on the 998 gearbox and it matched up perfectly so it could just be the way i was looking at it.
if your wondering, both engines aren't good but the 998 is better so its being built first so i can be on the road again

thanks, Adam

[HarrysMini]

I think the only difference is the Final Drive Ratios, other than that they're the same.

 

i could be wring though, so await clarification.

[pmplovesminis2006]

your right they are the same just final drive ratio differences

[Mini Mad Drakeley]

Ok well that's pretty handy, would it be recommended to change the final drive for the 998 one or keep it and just use it?
i will work out what the final drive is later when im home as obviously that will determine wether its compatible

[dklawson]

In your case they probably are the same gearbox casing.  

 

On the VERY early cars, the gearbox casings for the small bore engines were narrower than those of the big bore A-series.  That meant the 1275 crank could foul the inside of the gearbox casing if you tried to put it on top of a small bore gearbox.  However, you could easily put the 1275 box under the small bore engines.  This was corrected this by the early/mid 1960s.

[Cooperman]

I once had to put an A+ 1275 engine onto an early 3-syncro straight cut close ratio box. The big ends hit the gearbox casing, so I had to file the necessary clearance from the gearbox casing by removing about 1/8" of thickness locally and keep re-fitting the engine onto the box to check, finally using bits of plasticine to check that I had the 0.050" clearance I thought necessary.

[Mini Mad Drakeley]

So if i understand correctly then, the gear boxes are interchangeable across all models but fitting a 1275 to certain 998 boxes can be problematic, so fitting a 998 onto a 1275 block should be childs play

thanks for the help, Adam

[dklawson]

So if i understand correctly then, the gear boxes are interchangeable across all models but fitting a 1275 to certain 998 boxes can be problematic, so fitting a 998 onto a 1275 block should be childs play

 

I assume at the end of the sentence you meant to say "998 onto a 1275 box" not "block".  If that was your intent, then yes... you should be able to put a 998 engine onto the 1275 gearbox without issue.