T25 5 Speed Gearbox

[MrBeard]

Hey guys

I am considering replacing my 4 speed for a 5 speed.
But first I have some (probably stupid) questions.

I see more 5 Speed Diesel gearbox's, I have a Watercooled 1.9 petrol. I am guessing it would not take a diesel box?

Is it relatively easy to swap them, or do I really need a mechanic?
Will it mess with my Insurance?
And the point of this Will I finally be able to do 70mph without draining the fuel tank?
atm it's great at 60mph but that extra 10mph is an expensive luxury.

Will I need new Linkage?

Cheers
MrBeard
1986, T25 Watercooled with LPG 4speed

[Plasticman]

wiki^^^^^^^^^^^^
Id stick with 4sp,
if you were to change then you should get sick and box, fr-rr linkages, fittings on side of box, bell housings to swop etc etc, you also need to find the code for your box swop, and as for getting more speed for less fuel ask yourself how in the world you can get more for less? the effort required to propel ones bus an extra 10mph is considerable and this is bought/paid for in £uelllllll, you would also run the risk of gearing the bus in such a way as to not be able to rev out in shall we say ,top gear.
mike

[colinMSC]

you could do what we did and fit bigger tyres on the back,
we used a set of ford granada wheels with frontera 4x4 town and country tyres [big and fat]
did affect accelaration a bit but we were getting 38mpg [1.6d engine] even so 70 was its limit [flat out]
was verry good at 60 .

[Plasticman]

yep I have big boolies on mine and as you say 1.6 asthmatic is happy at 55-60 dont think mit will quite pull 70 accordingto the sat nav.
mrbeard is your box goosed or are you just thinking to change in the hope of the speed /economy thing
M

[MrBeard]

yep I have big boolies on mine and as you say 1.6 asthmatic is happy at 55-60 dont think mit will quite pull 70 accordingto the sat nav.
mrbeard is your box goosed or are you just thinking to change in the hope of the speed /economy thing
M

gearbox is ok. looking for improvement...

[Aidan]

gearbox is ok. looking for improvement...

5 speed doesn't give you much more economy especially on a petrol, it's not an overdrive fifth, it's virtually the same, it's a low first for towing, stick with the 4 speed, stronger box; chances of finding a good 5 speed are slim

if you want speed and economy get a T5

[California Dreamin]

As final drive ratio gets taller 'torque' reduces so you could easily find yourself in a position of theorectically having a higher top speed but a reality that the engine simply does not have the power to get there....you may infact decrease the vans top speed and end up playing a tune on the engine going up and down gears trying to maintain your speed.

Depending on the box a 5sp might only offer a marginal increase in final drive ratio....5th gear is not an overdrive.

The cheapest way to lower the engine revs a little is to increase the circumference of the rear driven wheels...but don't go mad.

Martin

[MrBeard]

Sounds like the only route is a rebuilt engine, with after market parts to get the higher bhp...

damn, more expensive... oh well, any other ideas?

MrBeard

[MrBeard]

The cheapest way to lower the engine revs a little is to increase the circumference of the rear driven wheels...but don't go mad.
Martin

what size would you recommend?

cheers
mrbeard

[Plasticman]

well Im runninnig 195x 80x14's quite a big circumference, has given just the right ammount of gearing , Im 1.6na, so I can just rev out on the flat which is how I like it (thats with a 5 sp but same principal for a 4sp)
mike

[California Dreamin]

Sounds like the only route is a rebuilt engine, with after market parts to get the higher bhp...

damn, more expensive... oh well, any other ideas?

MrBeard

Well.. a very popular solution would be a scubby conversion....all the modified parts that enable the conversion are now readily available from RJES? components.
Basically more power with better fuel consumption.
Look in the engine mod section.

Martin

[MrBeard]

Well.. a very popular solution would be a scubby conversion....all the modified parts that enable the conversion are now readily available from RJES? components.
Basically more power with better fuel consumption.
Look in the engine mod section.

Martin

Having looked at RJES, that is a really expensive option...to get them to do it, is about £4k, and the fuel economy doesn't seen any more than 4mpg better!!1

What am i missing?

MrBeard

[Plasticman]

Im not sure now just what you want you cant have more performance and hence more speed, go faster etc and have better fuel consumption its one or the other.dont matter wether its a car.bike lorry aeroplane.
M

[MrBeard]

hence my desire to change ONE thing.
I have crap fuel economy at 70.
having a vehicle that can handle the speed better (= a faster van) 90% has better fuel economy at ordinary speed than it did before.

I never said i wanted BOTH.

What I asked for was help figuring out which route was the best method to get the fuel economy at 70
gearbox or engine....

Cheers

[Ian Hulley]

What am i missing?

MrBeard

Simple really, you've bought the wrong van.