BJ40 4 Speed to 5 Speed Conversion

[jim land]

I daily drive my bj42 , 3b h55 with 33" tires and 4:11 gear , you have to learn driving it so you keep the momentum.
A turbo is definatly on my wish list with new head gasket , pre cups , exhaust and more ...

 

[OffRoad911]

I daily drive my bj42 , 3b h55 with 33" tires and 4:11 gear , you have to learn driving it so you keep the momentum.
A turbo is definatly on my wish list with new head gasket , pre cups , exhaust and more ...

It seems getting the H55f conversion makes the vehicle less powerful. Why are people then crazy about getting the 5 speed upgrade if there is a loss of power at top end?

 

[1911]

It seems getting the H55f conversion makes the vehicle less powerful. Why are people then crazy about getting the 5 speed upgrade if there is a loss of power at top end?

To keep the engine revs lower on the dual carriageway/motorway. More of an issue in the U.S. and Australia than it would be in the U.K.

 

[jim land]

No power lost, but 5th gear is only good on level road or going down a hill without a turbo

 

[OffRoad911]

To keep the engine revs lower on the dual carriageway/motorway. More of an issue in the U.S. and Australia than it would be in the U.K.

Just spoken with the mechanic and he assures me that after he has bored out the engine to increase its capacity to match a 2B engine. He suggested, I will for sure improve fuel efficiency, power but may suffer a slight loss of power when flinging uphill in the 5th.
Don’t want to go for the turbo option at this stage.

 

[1911]

Just spoken with the mechanic and he assures me that after he has bored out the engine to increase its capacity to match a 2B engine. He suggested, I will for sure improve fuel efficiency, power but may suffer a slight loss of power when flinging uphill in the 5th.
Don’t want to go for the turbo option at this stage.

The 4th cog in the H55 is a 1:1 ratio just like the top gear in the H42 or H41 four-speeds, so if power is lacking, just leave it in the lower gear. The overdrive 5th gear is a nice option to have when the road is relatively flat.

 

[gerg]

Just spoken with the mechanic and he assures me that after he has bored out the engine to increase its capacity to match a 2B engine....

That's a 6% increase in displacement. To put that into perspective, it's roughly a 5% difference in air density from summer to winter in most countries that are blessed enough to experience it. I'm sorry to say it, but those are low enough numbers that it might not be possible even to perceive a difference let alone consider it a signifigant improvement.

 

[Splangy]

Just spoken with the mechanic and he assures me that after he has bored out the engine to increase its capacity to match a 2B engine. He suggested, I will for sure improve fuel efficiency, power but may suffer a slight loss of power when flinging uphill in the 5th.
Don’t want to go for the turbo option at this stage.

Uphill in 5th? There will be no uphill in 5th!

Your mechanic has clearly never driven an old B series engine!

 

[bcsteel]

Down hill in 5th..

 

[gerg]

Down hill in neutral overdrive

 

[cult45]

Ex-BJ40 owner here, though I was lucky enough to run the 'big block diesel' aka 3B. Lol. It was my daily driver in Cairns [flat, 100k people, very little traffic, epic off-road/camping/fishing lifestyle] and Brisbane [hilly, 1.2m people, bad traffic, city life]. It had a 4 speed, Fairey overdrive, 4.11's and 31's. It also had no top, so there's a good couple hundred kilo's.

Honestly, it was a slug. As others have said you kinda have to fight to keep up with modern traffic. I'd hate to have the a/c on! Off road however it was unstoppable. Toyota designed these things [mostly] for off road use. It wasn't until the late 80's that improvements were added for more comfort and highway use.

But they can be made to work in modern driving conditions.

Money no object I would:

1. Ditch the B and run a 13B-T.

OR.

2. Freshen up the engine with boost in mind. Low boost turbo, around 10psi. H55. Disc front, single slave FF rear with FJ80 booster and master. Keep the 4.11's. 60/75 series power steering. Air if you can. 33's for fun.

FYI that H55 is a 60 or 70 series unit. Unless it came from a BJ60 or a BJ73/74 then it has the wrong input shaft and will need to be changed to mate to your B. Which brings me to my last point: Some of the work those third world shops do is incredible and ingenious. Some is not up to scratch. Pay your due diligence!