Morris Minor Owners Club

I've got a 1098 / 4 speed in my recently bought Traveller. I'm using it for a daily commute using dual carriageways so it would be less strain if it had a 5th gear, I assume. Is it worth the expense of a 5 speed box (I'd have to pay someone to supply & fit) or is the difference negligible at 60mph? And does it change fuel economy significantly?

a cheaper option worth considering (sorry to get in before you Roy) is to fit a 3.7 or 3.9 dif as this will lower the revs to the same extent as fitting the ford type 9 box at 60 / 70 mph and is cheaper than going down the type 9 box. I use the word cheaper in context as the dif alone will be around 150 ish plus fitting, but would cost less to fit than a type 9 box.

The cost of the type 9 box conversion kit is 550 to which you need to add a box plus fitting.

the disadvantage of the 3.7 dif is that unless your engine is in fine fettle you will find you are having to work your engine hard around town to get any acceleration ( so any gain in mpg is lost in town having to work your engine harder), this is not a problem with the type 9 as the ratios are very similar through the gears.

some one is selling a toyota 5 speed box in the sales section currently and might be a cheaper option than a type 9 box

all routes would lead to a more relaxed cruising but even with the high cost of petrol neither would pay for them selves very quickly i would have thought, unless you are doing very high mileages.

Hahahaha ^^^^^... As Charle says - a complete 5 speed box will cost you ~ £1000 installed - and with a standard 1098 you will rarely be able to use the 5th gear for any length of time. Fuel economy will not be significantly better. I run a 3.7 final drive with my modified 1098 and it's great - with a standard engine - a 3.9 will be better suited - by is it worth of hassle of changing from 4.22 to 3.9 ?? I doubt it - and again - fuel economy will not change to any significant extent.

is the difference negligible at 60mph?

Fairly negligible I'd say.
As long as the engine is in good fettle, valve gaps set, non rattling timing chain and the exhaust isn't leaking, then it's worth having a look at the sound proofing, even as new it was very basic.
Have a search on here for several threads about it.

i have 3.9 diff on a 1098 it has advantages and dissadvantages the good points lees noise cruiseing on the motorway the bad points you loose get up and go and climing abiliaty on hills .

Thanks all - based on your responses I think I may look at the sound proofing first. I know there've been discussions in other threads about motorway speeds but mine seems quietest (relative term!) around 58 and also around 65mph. In between those its causing a bit more resonance so sounds rougher and louder.

and with a standard 1098 you will rarely be able to use the 5th gear for any length of time. Fuel economy will not be significantly better.

I've only ever heard that said by folks who've not tried it.

Changing the diff ratio (which is much more common) gives a higher gearing for dual carriageway speeds and using a 3.9 diff is similar difference to 5th gear in a ford box with standard 4.22:1 diff
Funnily enough no body using a 3.9 diff with a standard 1098 complains they "can't use top gear for any length of time"... They do notice the difference going up-hills though - which is where a 5 speed box will win hands down.

Therefore if you live in a hilly area (e.g. bath area), the 5 speed will do you better than a 3.9 diff and definitely better than a 3.7
If you rarely hit big hills, the 5 speed box is probably overkill.

I ran a clapped out standard 1098 with a 3.7 diff and loved it almost all the time (except when visiting hilly parts of the country where I'd struggle on hills.)
I've run 4 and 5 speeds on 1098s 1275s etc.. I've even run a 3.7 AND 5 speed (which is a poor combination for a standard 1275, but it was like that when I bought it, and in that guise 5th gear was pointless - previous owner was planning a big HP increase when they chose it)

As for th cost - to reduce cost source the parts yourself and do most (or all) the work yourself... if poss ;-)

Aye -but is the 5th gear worth ~ £1000 ?? And is the 5th gear really just like a 3.9 final drive ?? Doesn't seem like much of a change from 4th to 5th then?

Laycock overdrive

On a Dolomite gearbox - has been done and works v well I understand.

It helps chomp through the tall gears . Love it .

Is yours on a Dolly box?

Spitfire , but it was all marina ital so the box was exactly the same, had to change the first rotational shaft and first gear , my prop needed some work on it anyway . Gives people a surprise when they hear me change thee gears then three more . It's a bit loud .
But l have heard of people using just the od unit in the drive train

5th or overdrive is more like a 4.22 to 3.7 or 4.55 to 3.9 - something around 0.85.

Yes - that's what I thought Richard.

I use in third too , flick it off pop it fourth ,use fourth and flick it back on .
Very useful at lower speeds when thirds too low and fourths too high , 3rd 1/2