90 Transfer gears & tyres

Hi Guys
I have a 200tdi 90, I'm thinking of having the gears in my transfer box changed to Disco gears to lower the revs. This is ok for a 200 tdi on 235/75/16 tyres but I was wondering how it would be if I were to swap tyres to 235/85/16? Will the gearing be too high or will the engine pull them ok?
Thanks Tigger

it seems alot of people have had different experiences with this, I had a disco box put on mine, at the time had 235/85 tyres, drops the revs nicely but impacted on performance.

Even with the fuel pump and turbo cranked up would struggle to accelerate after 60mph and would top out at around 70 unless you went full throttle which just produced lots of unburnt diesel smoke and might get you a couple more mph. Not sure what it did to the torque curve but also struggled more when you got to a hill.
Off the road the higher gearing takes a bit of adjustment.

I've gone back to a 1.41 ratio box now, so it goes better on the road and the low box on the disco one started whining.

Other people with tdi's however say its worked great for them, as i'm sure someone will comment.

thanks for that, as I'm going to have my own box re-geared I'd like to get it right. The main aim is to reduce the revs, not sure if 235/85 on their own will do this enough.

I used to run a 90 on 235/85 and 7.50's with 200tdi and disco transfer box. Had no problem with it even towing.
Wll be changing to one on my current 90 soon too.

can you just change the internals or the defender box? which bits do you have to change?

high gear on diff and intermediate cluster and input if 1.2 is 28 tooth input gear as defenders are 26 and disco 28 after e suffix low gear same in all

i have a 1.22 disco box on my 300 tdi 90, with 235/85's on. My 300tdi is well tired, and down on power and it pulls well above 60/70+ its just noisy.

Performance wise, its great. Really wouldn't bother putting the old one back on, the 90 really goes well.

Thanks guys that's really helpfull. I'd like to keep the low range gears the same, are the low range gears the disco box the same as a 90's? If so would it be better to do a straight swap for a disco box. I assume this has to be off a 200tdi disco, or would one from a 300tdi fit?

low range is same in any lt230

a 300tdi xfer box is the same. I have a 300 tdi box on my NA gearbox

Thanks guys top advice, I'll get to it. Cheers