Thread: 4BD1 performance

Originally Posted by yt110

Hi my vehicle is an 86 county no turbo but a 2 1/2" exhaust,3" raised air intake and a hyclone.I have 235/85 muddies on disco rims,I don't know what revs it doing as said by wovenrovings it would do 100kph in 3rd (down hill) now its in 4th and pulls very well,5th is just good cruising.I have not noted any change in fuel useage.All up loaded incl. camper trailer 4 tonne home(adelaide hills) to cape york and return 12L/100km ok me thinks. Jim

So that's the LT85 gearbox?
I'm running an Isuzu box, the ratios are very different and my rangie tyres are 225/75/16
With the old 1.22:1 transfer 3rd gear would topout around 60km/h, now it's over 80km/h but nowhere near 100.
4th gear should give me 135km/h and 5th 175km/h.
Averaging 10km/h in a rangie that's a bit more slippery shaped than a county.

Originally Posted by Dougal

So that's the LT85 gearbox?
I'm running an Isuzu box, the ratios are very different and my rangie tyres are 225/75/16
With the old 1.22:1 transfer 3rd gear would topout around 60km/h, now it's over 80km/h but nowhere near 100.
4th gear should give me 135km/h and 5th 175km/h.
Averaging 10km/h in a rangie that's a bit more slippery shaped than a county.

Yes its the LT85 box In some books I have it shows .996 ratios as in some 4 speeds,others show 1.222 ratio,the engine output shows 66kW in some and 72kW in others withturbo its 86kW so who knows what bits are used.But I found that loaded (as mine always is) I didn't have the power to run .996 Turbo was an option but I felt 1st high was still too high in the 5speed. As the main use of my landy is off roading how fast it is on road isn't that important, hence the ratio change,this may not suit everybody but in my case it made a very good 4x4 even better.

Originally Posted by yt110

... and a hyclone.

Would Sir be interested in a fuel catalyst as well??? Blinker fluid? A muffler bearing? Or perhaps some snake oil?


sorry - couldn't resist.

Here's the official power/torque for what I think is a truck based 4BD1.

Originally Posted by isuzurover

Would Sir be interested in a fuel catalyst as well??? Blinker fluid? A muffler bearing? Or perhaps some snake oil?


sorry - couldn't resist.

Blinker fluid ? it that the new lot for L.E.D.'s?

100k's/hr in 3rd by geese, i'm sitting at 2250rpm on 35's with my 5speed (LT77) and she is screeming! i'd be lucky to get to 60 in third!! hmm i suppose you've got airconditioning too

Originally Posted by def-90

100k's/hr in 3rd by geese, i'm sitting at 2250rpm on 35's with my 5speed (LT77) and she is screeming! i'd be lucky to get to 60 in third!! hmm i suppose you've got airconditioning too

You've got an Isuzu mated to an LT77?

Originally Posted by Dougal

...............4th gear should give me 135km/h and 5th 175km/h......

*cough* I'd be scared at those speeds in a nice new defender with perfect suspension etc... my county, 110km/h is about as fast as I feel comfortable with - not to mention driving in Victoria and doing 150km/h is ever so slightly frowned upon!