Ideal gearbox for a DJ?

[kevtherev]

I have a DJ engine coupled to a DG gearbox
What differences are there?

Could the differences, (if any) be addressed with a small percentage increase in overall wheel circumference?

[Aidan]

Kev

without knowing the codes of the boxes involved it's like people asking if a five speed will be quicker than a four speed, but yes if you want a bit more mph for less revs to use the DJ power (are you running it as DJ with fuel injection at 10 degrees and 98RON or at 5 degrees on 95RON or on carb mostly on gas as that makes quite a bit of difference to real world power output, as does exhaust system and inlet system) then going to 195R14C will make a difference

There are several different boxes (4 and 5 speed) for the 2.1 DJ and several different boxes (again four and five speed) for the DG

the biggest variation stock is AAP, the longest geared 5 speed, fifth gear is 3.7474, verses DU four speed from a DG fourth gear is 4.131 which is a 10% difference, so if your van is no heavier than a laden Caravelle and your engine has the get up and go of a full blooded DJ then you could run 10% larger tyres on the later box and have the final gearing of the former - there are boxes in between, ABN five speed from DG is only 6% different to AAP, ASM from DG is less than 4% difference

You may also see a change in fuel economy, though that may not necessarily be for the better; a set of tyres maybe cheaper than a replacement gearbox but could still be a few hundred quid spent for little gain unless you need new tyres and the few hundred quid will buy you another weekend or two's fuel

? whilst I'm posting why the lift pump and second fuel pump set up I wondered, what's wrong with standard fuel injection pump ?

FYI Shepster's non standard four speed has final gear of 3.9606 which is same as the ABN five speed

[kevtherev]

Many thanks for your reply Aidan
To confirm, I am moving from a carburated DJ 2.1 engine on LPG (10 deg) (early exhaust) 16" wheels, to a fully fledged factory injected system, LPG and late exhaust, transplant .

I liked shepsters long 4th and want to work toward that.
But until funds allow I was considering a tyre change, which has to happen soon anyway
I'll take a look at my box code

The new engine will have a standard DJ fuel pump, I was unsure if it needed a lift pump to my exterior swirl pot.

[Smiffo]

Many thanks for your reply Aidan
To confirm, I am moving from a carburated DJ 2.1 engine on LPG (10 deg) (early exhaust) 16" wheels, to a fully fledged factory injected system, LPG and late exhaust, transplant .

I liked shepsters long 4th and want to work toward that.
But until funds allow I was considering a tyre change, which has to happen soon anyway
I'll take a look at my box code

The new engine will have a standard DJ fuel pump, I was unsure if it needed a lift pump to my exterior swirl pot.

Hi Kev.

I think my gearbox is ABN. I have a dg engine with 16" wheels too.
If it helps I can findout what size tyres I have and tell you what revs I get to at 70mph.

What I can say from memory is that the van feels most comfortable with engine speed at about 60-65.

I have contemplated larger tyres or longer gearing too. First feels a bit pointless and it runs out of revs too quick for my liking in 5th.
Having said all that, I have no idea if the gearing in the box is standard, so it could be a bespoke setup in there....

On the plus side I have a steep hill I go up regularly which third pulls perfectly for. My old solex used to have me changing third to second and back again all the way up lol.

Let me know if you need some numbers to compare etc.