20 replies to this topic

[skoughi]

I've taken the plunge and have given a gearbox rebuild a go. Stripped it down with no real issues and everything looks ok, to me, except for maybe excessive end float on the laygear but that's a problem for another day. So I'll be fitting a X pin diff and a rebuild kit with centre oil pick up pipe, nothing out of the ordinary. Seeing as it's all apart, it's an A+ box, I'm toying with the idea of a close ratio gear set but I'm not sure I'll be able to put up with straight cut gears. I've never been inn a mini with a straight cut gearbox so have no experience of what kind of noise they make. So I guess my only real option is the Minispares kit C-AJJ4032A? My Mini is naturally aspirated and I usually go 

on runs of 50 miles or more, and for the most part drive in a sensible fashion! I live up in the Shetland isles and our usual mainland port of call is Aberdeen, I'm hopeful of heading down to a few shows or events with her next year so any journey I make will be from there which could mean I'll be driving for a fair while. So is the extra cost of a close ratio set, money I could use on the next stage which is a rebuilt short block, really worth it for the driving experience seeing as it is all road use and possibly longish drives? I'd like to hear others experiences of these gears and do you ever think you should've spent the money elsewhere? .

    

[pete l]

Not worth it in my opinion. Not on a road car that is driver sensibly.

[Spider]

Usually Close Ratio Gear Sets are used to match an engine's narrow power band, when hotter cams are fitted, but this makes 1st Gear, taller and with many Sets (particularly straight cuts), quite tall. To off-set that, a shorter final drive is fitted so you can get away without giving the clutch too much of a hard time. I don't think that fits in well with your longer drives.

I feel that all the Straight Cut Sets are just too close to be sensible for Road Use. I'll add here though as far as any noise from the Gears go, in 4th Gear, it shouldn't be any different to how it is now.

If you feel you want / need a Closer Ratio Gear Set, the original Cooper S had closer ratios than stock and these were a Helical Cut. I feel these are about as close you can sensibly go for road use and maintain a respectable final drive ratio.

[Chris1992]

So I was in the same boat as you before I had my 1380 twin cam built. I was so torn on what setup to go for considering I do a LOT of motorway miles getting to shows and never trailer my car. In the end I went for a full straight cut close ratio setup and a 3.1 fd. At first I regretted it, as with the 3.1 and CR box combo I was no longer able to burn away from traffic lights, as you have to really pedal it to get it off the line smoothly now. The straight cut gears, while good fun at first, were also piercingly loud.

 

However!! I have now put nearly 2k miles on this setup since I dropped the engine in a few months back, and I have to say that on the whole I am very happy. Now that I have got used to the feel of the clutch, being able to rip it up past 30mph in first gear is hilarious fun (I do miss fast traffic light launches though). I also find that the CR box puts 2nd and 3rd in the absolute perfect place for country road blasts, and the 3.1 fd means I can cruise at 70 in relative comfort. Regarding the noise, as Spider mentions above, once you get into into 4th the gearbox quietens right down, and something else I have noticed is that as I've put more miles on it, the wine from the box has become much quieter. Definitely still there, but I can now hear my exhaust and stereo over it lol. I've fallen in love with the sound it makes when pushing it through the country lanes, and every person that gets in it always says "it sounds like a race car" 

 

One last thing to note, I am running around 125 bhp with 90 lb ft of torque from 3k rpm. 

[Tommyboy12]

So I run turbo setup through a straight cut close ratio gearbox with a helical drop gear set and 3.4 diff. That means you get the screaming 1st, 2nd and 3rd gear but 4th gear is effectively helical and therefore quiet(ish).

 

Personally, I went for this compromise because I wanted the reduced side loading on the gearbox but also wanted a 'quieter' cruise. Although I fully expect the shims to be taking a pounding on the drop gears.

 

I am however toying with straight cut drops because I want to push the power up and I think im on the limit for helical drops.

[Chris1992]

So I run turbo setup through a straight cut close ratio gearbox with a helical drop gear set and 3.4 diff. That means you get the screaming 1st, 2nd and 3rd gear but 4th gear is effectively helical and therefore quiet(ish).

 

Personally, I went for this compromise because I wanted the reduced side loading on the gearbox but also wanted a 'quieter' cruise. Although I fully expect the shims to be taking a pounding on the drop gears.

 

I am however toying with straight cut drops because I want to push the power up and I think im on the limit for helical drops.

 

What sort of power are you running? I have a helical drop set which makes a me a little uneasy when thrashing it, so I have considered changing over if the engine ever comes out again. I do remember asking for straight cut drops when the engine was built so I'm a little bit miffed about that, but it's also a blessing to be able to cruise in 4th without the noise lol. 

[KTS]

which gearset is your gearbox fitted with :  double-groove, single-groove or plain ?

 

the double-groove gearset has a much shorter first gear (..i think mainly to cope with the extra weight of hauling a metro off the line, but was also fitted to SPI/MPI cars?) which means having to thrash the engine in first to avoid bogging down when grabbing second.

 

single groove and plain A+ gearsets aren't too dissimilar, and both are a bit shorter across the range than the S/GT set.

 

you can also play around with the primary gear & first motion shaft combinations (4 in all) to effect the overall gearing

[skoughi]

Thanks for the views on this guys. I am using a 3.44 final drive at the moment, and do have a 3.1 sitting on the shelf, even though on longer runs I do tire of the endless droning and do wish to have a longer final drive I know that unless I invest heavily on more torque then I'm just going to loose the enjoyment factor on the twisty single track roads so will probably stick with the tried and trusted 3.44. So as far as I can see the "S" ratio kit that I quoted from Minispares cannot fit into the DAM5626 case, even with the earlier layshaft? So the only choice is a straight cut set, which is an unknown quantity for myself to see if I'd like it, and be able to put up with it, and as Pete says probably not worth it. Maybe save some pennies for other money pits. Or I could just blow the entire budget and go for the heavy duty helical close ratio set! 

[skoughi]

which gearset is your gearbox fitted with :  double-groove, single-groove or plain ?

 

the double-groove gearset has a much shorter first gear (..i think mainly to cope with the extra weight of hauling a metro off the line, but was also fitted to SPI/MPI cars?) which means having to thrash the engine in first to avoid bogging down when grabbing second.

 

single groove and plain A+ gearsets aren't too dissimilar, and both are a bit shorter across the range than the S/GT set.

 

you can also play around with the primary gear & first motion shaft combinations (4 in all) to effect the overall gearing

It's a single groove gear set. I was actually wondering about the drops and primary gear combinations, wasn't aware of first motion shaft options though. I'll need to do a bit more reading up me thinks! 

[GraemeC]

The SC kits aren't that noisy if you stick with helical drops.  Imagine the 1st gear whine in 2nd & 3rd.

 

The 1040 laygear can be made to fit a rod change 'box, but its not a drop in conversion.

[Tommyboy12]

 

So I run turbo setup through a straight cut close ratio gearbox with a helical drop gear set and 3.4 diff. That means you get the screaming 1st, 2nd and 3rd gear but 4th gear is effectively helical and therefore quiet(ish).

 

Personally, I went for this compromise because I wanted the reduced side loading on the gearbox but also wanted a 'quieter' cruise. Although I fully expect the shims to be taking a pounding on the drop gears.

 

I am however toying with straight cut drops because I want to push the power up and I think im on the limit for helical drops.

 

What sort of power are you running? I have a helical drop set which makes a me a little uneasy when thrashing it, so I have considered changing over if the engine ever comes out again. I do remember asking for straight cut drops when the engine was built so I'm a little bit miffed about that, but it's also a blessing to be able to cruise in 4th without the noise lol. 

 

 

Running 150hp/150ftlb at the wheels at the moment. I try not to go too hard on it in 4th but I am very wary of it for the same reason. The drop gear side loading if you calculate it is actually only like 10kg but that can quickly wear a shim out if youre not careful/drive a race car!

 

I did do *a lot* of reading up on helical gears/drops in a turbo application and got lots of differing views and opinions before I made my own decision but there are guys out there running more power on helical gears and drops without issues. Realistically I do about 3-4k miles per year and if I have to pull the engine out after 15k to replace shims then im still happy with that.

 

Im actually more bothered about the 3.4 diff I picked! I should have gone for 3.1!

[stoneface]

I'm running 132bhp/112ftlb and changing from SCCR gears and SC drops with 3.2 diff to A+ helical gears and helical drops with a 3.2 diff.

 

The noise was bad for a road car in my opinion, but they are like marmite and some love them. I prefer to travel in stealth mode and not be heard coming for miles.

 

Also the gearing was terrible for a road car with constant clutch slip required pulling away, and even worse if on a hill or car park ramp.

[pete l]

Quick question.

 

What's the point of having straight cut gears in the box if you stick to helical drop gears ?

[Spider]

 

I did do *a lot* of reading up on helical gears/drops in a turbo application and got lots of differing views and opinions before I made my own decision but there are guys out there running more power on helical gears and drops without issues. Realistically I do about 3-4k miles per year and if I have to pull the engine out after 15k to replace shims then im still happy with that.

 

The Idler Gear is the potential weak spot in the standard helical drops as you are already on top of. They will actually take a lot of power but - like anything - there's a few things that need to be done. I've found the most important is to match the Transfer Housing to the Gearbox Case. I know they are doweled and that gets them close-ish, but far from ideal on all I've checked. By matching them, the Gear will then run true in the bearings and across the whole bearing journal of the Axle rather than on 2 thin bands on each side. The other thing to do here is to lock the Thrust Washers to the Cases or stop them spinning. There's realistically, not enough meat in the cases to pin or screw them (through, I have seen that), I have used a 'carrier' to stop them spinning. These two mods alone will give a much much greater issue free life here when pushing them hard.

[johnR]

So I was in the same boat as you before I had my 1380 twin cam built. I was so torn on what setup to go for considering I do a LOT of motorway miles getting to shows and never trailer my car. In the end I went for a full straight cut close ratio setup and a 3.1 fd. At first I regretted it, as with the 3.1 and CR box combo I was no longer able to burn away from traffic lights, as you have to really pedal it to get it off the line smoothly now. The straight cut gears, while good fun at first, were also piercingly loud.

 

However!! I have now put nearly 2k miles on this setup since I dropped the engine in a few months back, and I have to say that on the whole I am very happy. Now that I have got used to the feel of the clutch, being able to rip it up past 30mph in first gear is hilarious fun (I do miss fast traffic light launches though). I also find that the CR box puts 2nd and 3rd in the absolute perfect place for country road blasts, and the 3.1 fd means I can cruise at 70 in relative comfort. Regarding the noise, as Spider mentions above, once you get into into 4th the gearbox quietens right down, and something else I have noticed is that as I've put more miles on it, the wine from the box has become much quieter. Definitely still there, but I can now hear my exhaust and stereo over it lol. I've fallen in love with the sound it makes when pushing it through the country lanes, and every person that gets in it always says "it sounds like a race car" 

 

One last thing to note, I am running around 125 bhp with 90 lb ft of torque from 3k rpm. 

The fact that you're getting wine from your gearbox is a compelling argument for close ratio gears! ;)