a series 998 auto to A+ 1275 auto

[loveb]

I know in australia there wasnt much options with regards to diff ratios for the autos. Infact I think we only got one diff ratio and I think elsewhere there was only one other option.

I've got a 998 a series in my mini at the moment. And at about 100kph its at roughly 5krpm. which while its alright and seems to do it (although I stick to about80-/90 most of the time) at that speed its definitely screaming and I would not mind having a slightly longer ratio to keep the revs down..


I read somewhere that on a rover 1275 auto 100kph is roughly 3.5k? is that correct? or was his speedo reading out? I was told there wouldnt be much of a difference. .But obviously between 3500 and 5000rpm there is a bit of a difference there lol.


I'm not looking to make a race car out of the auto. I'm putting the 1275 in just so it keeps up with traffic atleast. I'm just wondering if the rovers had a longer ratio so I could atleast sit on a highway without fear of the engine blowing up.

Does anyone here have a 1275A+ auto and can I get some insight please? there there diff options for an a+ auto?

[Spider]

The overall Top Gear ratio of the 998 Autos we had here is the same as a Mini Deluxe (or very bloody close) at 3.76:1 in top gear. At 100 kph your engine should be reving at (near enough) 4200 RPMs (23.8 kph per 1000 RPM).

There were a few ratios available, more so in later years, however be aware, that unlike a manual gearbox, it is necessary to strip an auto down to almost the last bolt to swap out the Pinion that forms part of the final drive, so it is a BIG job. Given that the gearbox would be stripped down so far, it's likely 'issues' would be uncovered that you'd want to sort out while you're in so deep.

If you did opt for a taller Final Drive (to drop the engine revs down), then it won't nearly be as responsive as want it is now and it will also load the engine more (most of the time). While revs do cause some wear on these engines, loading them causes heaps more. They will happily sing alog all day at 4500 RPMs (I did do a 'drive' once of 3000 km round trip sitting on 5000 rpms with no issues what so ever). My current 'touring vehicle' I frequently do 10 000 km trips in, much of the time sitting on 110 kph (4100 RPMs).

The Final Drive Ratio fitted to your Mini will be 3.27:1, however there is a drop through the drop gears, so you need to multiply the FD Ratio by 1.15 to get the overall ration from the crankshaft to the wheels, so overall it comes out at 3.76:1.

Other FD ratios available were;-

3.48 (very rare)
3.27 (as above)
3.1-ish - I can't lay my hands on this one right now!
2.76

I would suggest that you leave what's in there, I think you'd be somewhat disappointed going to a taller FD, especially given you only have a 998. Other than the engine reving slower and a drop in engine noise, there'd be no other advantage, only disadvantages.

[loveb]

True. The 1275 auto has a box too .Which I think has a slightly longer ratio? even if a bit... I might get a gps speedo app and see what speed I'm actually at at 5k. I'm fine with the speed in that sense. if its fine at 5k at 100kph thats fine. I wont take itlong distance too much anyway. I just want it to keep up with traffic too hahaha.

I will see how the 1275 standard auto goes. Then decide. its mainly only driven around town so I dont really have a need for it to be too long

[Spider]

Sorry, in all that I wrote there I forgot to metion I did an auto conversion on my (late) brother's Moke.

It was a 998 Manual and wasn't too bad given what it was (tired but stock), I then did the conversion which was from a 1275 Rover and had the 2.76 FD. It drove better on the 998 Manual than the 1275 Auto.

[loveb]

ayayay!

I'm gonna keep the 998 still as a spare and rebuild it!