21 replies to this topic

[welshdan]

As said bob the 3.4 sounds perfect. Give it a chance, like most new setups it will take some getting used to. Im not sure that with the 286 you will ever get the motor to be smooth pulling off/around town. There may be a small improvement lowering the fd, but this will make things much worse at cruising speed. Close ratio gearsets also have a tall first gear which may exaggerate the feeling that you may be getting

[nzmember]

Bob - SCCR set or just the old 1275GT helical set?

I have a 1293 with the 286 and I started off with a 3.44 diff on a SCCR set.  Although it would easily pull in all gears I found that ratio did not suit the torque curve of the 286 - I was forever off the power or having to hold it in each gear.  Now have a 3.9 and it is much better suited.  Yes, a pain on the open road but much more useful in the lanes snapping through the gears.  Might be different with a 1380 and the 1275GT gearset.

Yep, took the engine out (again) to change the diff.

 

[Old Bob]

Bob - SCCR set or just the old 1275GT helical set?

I have a 1293 with the 286 and I started off with a 3.44 diff on a SCCR set.  Although it would easily pull in all gears I found that ratio did not suit the torque curve of the 286 - I was forever off the power or having to hold it in each gear.  Now have a 3.9 and it is much better suited.  Yes, a pain on the open road but much more useful in the lanes snapping through the gears.  Might be different with a 1380 and the 1275GT gearset.

Yep, took the engine out (again) to change the diff.

 

 

Yes, running a 'Clubman' SCCR gear set (courtesy of a Guessworks rebuild).  I appreciate it's always going to be a compromise but I fel it could be better......

 

Bob

[Cooperman]

The GT/S gear set is a much wider ratio set than the SC CR set. With the SC CR set the 1st gear ratio is high so a low FDR is necessary to enable pulling away without lots of clutch slipping and to keep it 'on the cam' through the gears..

I had exactly the same problem with an earlier Cooper 'S' after I fitted SC CR gears and with a 544 cam. It needed so much clutch slipping that 'off the line' acceleration was poor and clutch wear high.

I changed to a 3.9:1 FDR and it was fine. That is what I have with my current 1310 cc 'S' and it's great, although cruising at 60 mph is just over 4000 rpm.

The alternative for the OP would be a 266 cam, or even maybe a 276 and standard or GT/'S' ratio gears with a 3.44 or 3.76 FDR.

[robminibcy]

i have run a 286 with 3.4 final drive and found it the best setup ive had, best of both.

 

If your changing the final drive ratio, you might need to change the C bracket around the pinion. I had to change mine when going from 3.44 to 3.1

sorry to bring back up an old thread! i am finally getting round to actually swapping my FD. I am going from a 3.4 to a 3.1 as well. how can you tell if the c bracket wont fit? is it just a case of the pinion gear wont go in? if it wont fit can you just grind it back a bit or is it a case of getting hold of a differant one?

 

Finally if it needs a differant one how can you tel the new one will fit?

 

Cheers. dont mean to thread hyjack but op may find info useful anyway!

[Jordie]

Sorry I dont fully know, I had my local specialist do it as I didnt have access to all my tools at the time, so was far easier for them to do it.

 

I believe the clearence is tight around the small pinion gear. The specialist i used keep 1000's of spare parts, so swapped it over for me without any issue.

 

I would rather fit the correct part rather than grind/possibly weakening or damaging the current one. Its not so easy to access once the engine is in the car so its a case of doing it right the first time.

 

Jordie

[Guess-Works.com]

There are a number of different sized brackets for the gearbox.... All pre rod, so remote and magic wand will need to be modified to accept a larger pinion than the 3.4 ( 18 tooth ). A series rod and even some early A+ can also suffer from this issue, but most all later A+ will take the longer final drives...

 

You can grind it out, and I've seen it done many times, with varying degrees of sucess, but it's much easier and cleaner to machine it out on a lathe.