Gearbox Overhaul

johnymd

Club Member
Have you seen the prices of S14a boxes lately. I had been promised one but let down when it was sold to someone else, so I have been looking into gearboxes again. I would like to go the S14a route but do I want to spend the £900ish on the conversion? I hear they are very nice but I dont remember the 71 a&b boxes being that bad and for a pretty standard road car do you really need to spend this money.
 

tel240z

Club Member
£900 :eek: done mine probably 5 years ago with a short shifter installed supplied courtesy of a couple of forum participants I rely need to dig my blue Z out soon and let you have a go john
 

SKiddell

Well-Known Forum User
Hi JP

The difference between the 71a & b and the 71C is chalk and cheese, even a "good" original box is like waggling a mop in a bucket in comparison.

When taken apart you can see the engineering difference, the selection forks and yokes are significantly bigger as is the width of the gears and bearing etc., all in all giving a very precise shift that really fits the cars style where as a sloppy waggly gear lever fits somewhere in an MG.
 

morbias

Well-Known Forum User
Has anyone dynoed the difference in drivetrain loss between an S14 box and the older ones? Just curious.
 

SeanDezart

Well-Known Forum User
Hardly - not interested to know the diffeence of maybe, maybe 1bhp with all the other variables like diffs, half-shafts, tyres and sizes.....they're betetr full stop.

But I will say that the S14a is not imho the best* for a simple road car.

*'Best' taking into account price and feel.
 

morbias

Well-Known Forum User
Hardly - not interested to know the diffeence of maybe, maybe 1bhp with all the other variables like diffs, half-shafts, tyres and sizes.....they're betetr full stop.

ah but how do you know it's 1bhp (maybe) without any data? :)

I'd have thought it would be more given the big internal differences that Steve has mentioned. In anything other than 4th gear there could be significant differences, you might even lose power because of the wider gears. How much weight difference is there in the rotating parts?

Even if the difference is small I still find it interesting even if you don't :p
 

SKiddell

Well-Known Forum User
Has anyone dynoed the difference in drivetrain loss between an S14 box and the older ones? Just curious.

The biggest losses are at the tyres and the diff, differences due to gearbox changes will be marginal at best certainly not enough to put you off.

Sean said:
But I will say that the S14a is not imho the best* for a simple road car.

*'Best' taking into account price and feel.

I would agree, if your "thing" is to sit in a field polishing chrome whilst extoling the virtues of different wiper blades then you could get a better bang for your buck, but if you like driving your sports car in a spirited manner then its worth considering.

And as for cost, well I think £900 is where its at considering you interact with the gearbox as much as the brakes or steering
 

SKiddell

Well-Known Forum User
So an s14 box will lose more power than the older models?
possibly due to the larger gear bearer surface but its likely to be marginal most drivers won't notice a couple of HP and will be so taken aback by the transformation.
 

morbias

Well-Known Forum User
Ah ok, that's what I was wondering.

Are there any alternatives to an s14 box, say... something with 6 gears, or is it just that the s14 one is easier to make fit? I read the s15 ones are weaker and don't have the speedo drive.
 

johnymd

Club Member
£550-£650 seams to be where they're at now. Add the cost of bell housing and machining and that's how I get to £900ish.
 

richiep

Club Member
Those 5-600 quid ones seem to be via breaker/import businesses though (like those current listings from somewhere in Denmark). Privately they were averaging around 200-250 even quite recently. I was lucky at 150 though.

S13 boxes can had for under 200 and are a similar fit but not as preferred due to strength or different ratios I believe?
 

SeanDezart

Well-Known Forum User
I would agree, if your "thing" is to sit in a field polishing chrome whilst extoling the virtues of different wiper blades then you could get a better bang for your buck, but if you like driving your sports car in a spirited manner then its worth considering.

And as for cost, well I think £900 is where its at considering you interact with the gearbox as much as the brakes or steering

Yeah, you're in drive it like you stole it mode mate......the reality is that not everyone wants to thrash their Zs up and donw in straight lines or like the grown ups going up AND down the gears with corners and things.....some like to give it a little stick and that's all the Z gets each week or each month and an S13 box at £200 is a more reasonable outlay than £900 (which is cheap for a top quality perfomance box WHERE and WHEN needed) and if someone here is asking on behalf of a 280ZX, I belive that your view expressed here that it's an S14A or nothing is not helping the guy make an objective decision to move away from an OEM box.:thumbs:

I've driven Zs now with each type of bow in and the S14a with a quickshift is lovely when in a car that demands it but my first box in the yellow Z was an S12 and I was no slouch and it coped perfectly with whatever power my L31 was putting through it.
 

Huw

Club Member
It would appear my question has sparked some lively debate around this topic, which is a good thing as I've learned quite a bit.:thumbs:

I am unashamedly a 'stick the car in a field and polish it' owner, if you've seen my car that will stand to reason. But I do like driving it hard when the opportunity arises so I'm not looking for sparkling performance just an improvement on what I have, which at the moment is a knackered gearbox. I am going to go down the road of swapping the box probably to an S13 as money is as always a factor and £600 plus notes on the box alone is not an option for me. Having done a fair bit of searching on the topic I am still left with some areas that need some practical answers.

What mounting mods will need doing, is there a pattern so I can copy it?
Is there an issue with the speedo, not seen anything to suggest there is but will the existing cable and drive work? If not how do it sort it?
How much do I need to shorten the prop by, having just paid for one to be made I don't want to bin it.
Machining the bell housing seems straight forward however, as I found a good article to help me with that and I think I can now do that my self.

So any of the above that can be answered I would be grateful, I do intend to make a few calls on people mention so far anyway.:p

Thanks again for the advice so far.
 
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