15 replies to this topic

[HarrysMini]

Hello everybody,

 

Just had a thought, possibly a stupid one, would it be possible to put a mix of straight cut drops and helical gears in a case?

 

I know pretty much nothing about gearboxes as I haven't yet spent much time with them or researching them, my main focus has, up until now, been the engine.

 

I plan on fitting a 3.75 FD to give me acceleration as I will only be using it on motorways very rarely, and I don't need a high top speed... As long as it can do 70 :)

 

One more question, is whine from a standard gearbox normal? I have been told that all gearboxes whine to a certain extent, it's just modern gearboxes are better soundproofed.

 

Thanks guys

Harry

Edited by HarrysMini, 13 May 2013 - 03:02 PM.

[Artful Dodger]

my friend, you need to reaserch gearboxes alot more:)  the drop gears are what transfers the power from the crankshaft to the input shaft of the gearbox. what would be possible and not have a huge whining noise is to have helical drop gears and a straight cut gear set. this would be quite nice, but literally would be pointless apart from the noise. 

 

all normal gearsets have straight cut 1st and reverse gears. 

[HarrysMini]

my friend, you need to reaserch gearboxes alot more:)  the drop gears are what transfers the power from the crankshaft to the input shaft of the gearbox. what would be possible and not have a huge whining noise is to have helical drop gears and a straight cut gear set. this would be quite nice, but literally would be pointless apart from the noise. 

 

all normal gearsets have straight cut 1st and reverse gears. 

Sorry, that is what I meant. I've only ever read about straight cut drops. 

So I would get a set of helical drops and a set of straight cut gears? Sounds expensive for just some noise.

 

As I said I haven't even looked into gearboxes until now, this is literally my first day of reading about gearboxes... I better do some reading before I bother you with my stupidness.

Thank you for the enlightenment.

Edited by HarrysMini, 04 May 2013 - 12:14 PM.

[cradley-heathen]

hey mate we were all new to this once! dont worry about asking questions!

 

i agree with above though, that combination would be your best bet, but you are right its quite an outlay just for the glorious noise! there are obviously other benefits to them, but depending on your engine spec and what you use the car for you arnt likely to make use of them.

[Old Bob]

Don't worry Harry - if some of us didn't ask stupid (to those who know) questions, how would we ever learn?

 

Thing is, it is the straight cut drop gears which give that distinctive sound.  Not possible to have them on for some of the time so you either go for noise or comfort.  Straight cut gears are (this is where theory and practice seem to differ) stronger, but for all normal driving are not superior to helical gears which are quieter.

 

And yes, most old gearboxes whine - it is only when you switch from a modern to a classic car and back, that you realise how much progress has been made.

 

Bob

[HarrysMini]

Thanks for the info guys, much appreciated. 

In that case, I probably won't go down the straight cut route. At first it's a bit of a laugh having whining gears but one or two years time down the line, the novelty would probably have worn off and they would start to get a bit annoying.

I do quite like the subtle whine you get from standard helical gearboxes, so I'll probably just stick with that and spend my money rebuilding my knackered gearbox I have at the moment. I will also think about getting a cross pin diff, but that's for another day.

 

Thanks again

Harry

[Artful Dodger]

Yeah bud don't bother with straight cut gears:P they will just annoy you after a while! Save the money and get better manifolds:D more power!

[retroracer1275]

I got straight cut drops just because my neighbours enjoy the sound of them early in the morning  WORTH IT!

[Artful Dodger]

^. And he is an evil bsterd

;)

[jaydee]

1st and 2nd gear are the noisier in a straight cut gear set, 3rd and 4th are bearable

[mini13]

1st is straight cut as standard anyway,

 

what you can do is run a straight cut gear kit and helical drops, as the box drives straight through when in 4th it will be pretty quiet, but you'll get the benifit of the strait cut 1,2 and 3rd.

 

generally the most you can put through the helical ox is about 120-150hp, but you can get away with a fair bit more through the helical drops. Ivanhoe on here has been running helical drops at well over 200hp for several years with no issues.

[jmmini]

With my straight cut box I have concluded is like paying to have your ears rendered useless :L

However they do directly transfer power more efficiently than a helical cut effort, you need to decide if you want to have a daily driver or a daily whiney (but annoying cool) mini

As said before, if your looking for PAWWA you should start off some engine/exhaust tuning, maybe a minispares stage 1 kit?

Edited by jmmini, 04 May 2013 - 04:56 PM.

[HarrysMini]

Power's not an issue. At the moment, in this particular engine, I'm running a 998 bored out to 1062 with a lightened flywheel, 12g295 polished head, Maniflow twin box 1.75" exhaust, Maniflow cooper freeflow manifold, Maniflow alloy inlet manifold, K&N cone air filter. My Uncle has an uprated cam (don't know what it is) and a twin HS2 setup he said I can have as he sold his Mini a while ago.

 

My next job is the gearbox etc. I plan on getting a cross pin diff with a 3.7/3.8 FD. Following your advice, I will be doing a full gearbox rebuild instead of a SC setup as it would be more beneficial.

 

I'm running on 10s so as you can tell I'm looking for acceleration as opposed to top speed (as long as I can get to about 65-70). I have been told that with my current setup and the extras I plan to fit in the future, I should expect a 0-60 of about 8 seconds. That's faster than a Golf so I'm happy. I haven't actually got a car to put the engine in yet so I won't know for a while... I don't even know what sort of BHP I'm getting!

 

Thanks for your help everyone, you have probably saved me a lot money. Please forgive my initial stupidness.

 

Harry

Edited by HarrysMini, 04 May 2013 - 10:27 PM.

[Ethel]

It would be worth your while, and interesting, to clue yourself up a little bit on gearboxes. There are 3 shafts (ignoring reverse). The first motion, or input, shaft is end to end with the 3rd motion, or mainshaft - locking them together into a single shaft gives you 4th gear (in a 4 speed Mini). To provide the other gears the input shaft drives a layshaft that is parallel to the other two shafts. It is a solid, single piece, with a gear at one end, permanently driven by the input shaft. There are another 3 integral gears, of varying sizes, to give 1st, 2nd & 3rd. Each gear permanently turns a paired gear that is free to turn around the mainshaft. You engage any particular gear by locking it to the mainshaft, turning it and consequently the final drive via its pinion gear fixed to the shaft's end.

 

So, as you can see, all the gears are permanently meshed and you'd need a special, half helical - half straight cut, layshaft. Though, when you're in top (4th), the drive is in a straight line from input to output with all the other gears unloaded & idling.

[HarrysMini]

Thanks Ethel, I really do need to read about gearboxes, as I say, I don't really understand how they work as I've been focusing on other things. 

Does anyone know any good resources or websites that give information about gearboxes (especially ones to do with Minis)?