Altering gear ratios

[talkingcars]

I have a 2.0i MG Maestro and do a lot of motorway milage, how easy would it be to change 5th to a longer ratio to give a lower engine speed.

James

[tony]

the easy way would be to fit a gearbox from a differnt car, not sure which model would be best tho:)

[E_T_V]

Have a search for previous posts

Take a look here: http://www.maestro.org.uk/temp/gearboxdata.doc
and here: http://www.maestro.org.uk/forums/showthread.php?s=&threadid=171&highlight=gear+ratio

[MGTurbo]

I always felt the problem with my EFi was it revved too high in 5th. Ideal solution would be a K6 box with a diesel 5th gear.

Gareth

[e692wtt]

As a 'straight swap' how's about swapping the gearbox (complete) with one from one of the 'cooking' models, ie non-MG EFi Montego 2.0 ?

These are geared at somewhere between 25 and 27mph/1000 engine rpm (depending on wheels fitted, ie metric or conventional, and possibly on which model the gearbox is from? The figures vary from road test for the non-MG models so this is conjecture...) whereas the MG Montego 2.0i of 1984 was geared for 20.6mph/1000 engine rpm (I believe the MG Maestros were similar - root of your problem...) but the Turbos were geared at 25.0mph/1000 engine rpm (Montego 1985 model and Maestro 1989 model).

All info from 'Guinness World Car Record, in conjunction with Autocar, by the way...

So basically any Honda PG1 gearbox from a 2.0 Montego that isn't fuel-injected will suit you better than what you've got now. The gearing will be longer in all gears (ie the engine will rev more slowly for a given road speed in all gears compared to with the current box) but it will be a straight swap.

:)

[J199 HHG]

Get the box from a Diesel Montego Saloon.

Or look in the Haynes Manual for the Diesel engine - that lists all the ratios and gives gearbox suffix numbers.

[E_T_V]

Or read the info I posted above which has them all in :D ;)

[talkingcars]

Thanks for the replies, especially the links.

However I think most of it misses my question, I want to keep my current gearbox and dif, I just want lower revs at motorway speed when in 5th gear, in other words, is it possible to take the components for 5th gear from a gearbox for a non cooking 2.0 or, even better, a 1.6 and place them in my box.

James

[E_T_V]

You'd have quite a strange gear set up then, but if there are a pair of gears that "do" 5th and they can be removed then I guess you could. You'd need to study the exploded diagram for a while and make sure there are the correct clearances etc. Also stripping a gearbox is scary stuff :D

In an ideal world we'd all have 6 or 7 speed gearboxes.

[talkingcars]

In an ideal world we'd all have 6 or 7 speed gearboxes

A call to jack knight or KAD then.

Most of the lorries I drive have 6 speed boxes.

James

[G51 NAV]

Fitting a different box with the ratio you need should be a lot simpler than rebuilding the existing box with a new fifth gear.

What you need is an overdrive...

Hands up all those who remember what those were!

[H48HPE]

I hate to point this out but I was looking round someones new ford mondeo company car the other day and discovered that it has a 6 speed box,

[D87 SMW]

Originally posted by H48HPE
I hate to point this out but I was looking round someones new ford mondeo company car the other day and discovered that it has a 6 speed box,

Was it the 2.5 V6 Ghia X?

[BIGLAD]

Doesn't the "Honda" 'box have a 1 piece laygear in it?
If so, then not only would you have to change the 5th gear for a different one from another 'box (or have one made to suit your rpm requirments)but also have laygear made. I would imagine that this could be quite expensive?

[H48HPE]

Im not sure to be honest, it was an estate, It wouldnt have been a top model

[J199 HHG]

Overdrive?, I remember them. Then car manufacturers started fitting 5th gear, which does exactly the same job for much less weight.

Not sure about the requirement for 6 gears though. Why not have 4, a torquey engine, and space them accordingly. My Land Rover has a 4 speed automatic, and that appears to be more than satisfactory.

[talkingcars]

Doesn't overdrive give a higher ratio in every gear, I last came across it was fitted to a brand new transit van 10 years ago.

My lorry has 6 gears and I use all of them all the time, they are spaced closer than the 5 in our smaller lorries and makes it more drivable.

A 4 speed auto box in a land rover is perfectly suitable for the type of vehicle but wouldn't suit a "hot hatch".

James

[e692wtt]

An 'old fashioned' overdrive gave a higher ratio in gears 3 and 4 of a 4 speed 'box, via an electrical switch (eg Triumphs of the 60s and 70s) on the gear knob. Electrical problems were, errm, not unknown... And yes, a fifth gear is a lighter, more reliable solution.

An 'overdrive fifth gear', if memory serves, means that the said 'fifth gear' (in a 5 speed 'box) has a gear ratio of less than 1 (eg 0.82:1, whereas first gear in the same box might be, for example, 3.5:1)? If memory *doesn't* serve, then I'm sure someone will correct me...:laugh:

[E_T_V]

Our land rover gave over drive on all gears, giving you 8 forward ones to chose from :D

[D87 SMW]

Originally posted by E_T_V
Our land rover gave over drive on all gears, giving you 8 forward ones to chose from :D

Most of them do. It's a 4X4.

[e692wtt]

Subarus of the early 90s had a 'transfer box' to give 'low ratio' (ie low ratio...) and 'high ratio' (ie standard ratio) in all 5 forward gears (and probably reverse as well) for those 'sticky situations' - not the same as overdrive, but a choice of 10 ratios and four wheel drive never meant we got stuck on a Rally Stage - and, funnily enough, Monty might have been caked in mud but he always left Rally Stages (I was a radio-marshal) under his own power as well...:laugh:

And Monty kept up with Subaru Impreza 2.0s and Legacy 2.2 s on the way back as well... ie up to 100mph over long distances...:laugh:

Happy days.:)

[E_T_V]

Originally posted by F170 GGT
Most of them do. It's a 4X4.

Ok then if you want to be pedantic it had 16 forward gear ratios with a choice of 4wd or rwd.

[e692wtt]

Originally posted by F170 GGT
Most of them do. It's a 4X4.

Errm, 'the best 4 by 4 by half'... (Land Rover ad)

4 * 4 * 1/2 = 8 which is the number of ratios available when you use 'low ratio' (4 ratios) then 'high ratio' (another 4 ratios, different to the first four). 4wd (wheel drive) vs 2wd shouldn't come into it, but the vehicle in 2wd 'mode' will feel faster due to a reduction in mechanical inefficiency (ie turning less bearings as only one differential being used, only one pair of wheels being used to apply power to the road, not all 4).

;)

*later thoughts* the Land Rover ad was 'the best four by four by far'... :o oops...

I'm possibly making it up, but there would be 8 forward ratios (1st, 1st+overdrive, 2nd, 2nd+etc etc etc) =8 ratios... ie 8 'normal' gears. And then 'low range' to double your options (1st, 1st+overdrive, 1st low range, 1st low range+overdrive - that is 4 gears for 'first' already... multiplied by 4 = 16 gears available for what appears to be a 4 speed 'box...

Or am I making it up? It would appear a Landie has 16 forward gears...:eek: