The cheapest way to get taller gearing is fit larger tyres. 255/85-16s should fit with only a slight cut and shut to the exhaust. 35's need more work.

Swapping diff ratios gets expensive. Especially for a salisbury.

I assume you already have 0.996:1 T-case high range already?

??? AFAIK the tallest ratio available for the Sals/D60 is 3.54:1. The SD1 has rover diffs in 3.08:1 and 2.8:1, but that is no help if you can't get a matching rear.

Hi Ben, The Sd1 has 'salisbury' type rear ends dont they? with a watts link or similar like the XE falcon? actually Looks a bit like the XE falcon borg warner diff from memory...

Hmmm, Memory

Anyway, the overdrive will self destruct in 10 seconds behind the Isuzu, I have thought about using a Laycock type unit from a Volvo 740 Turbo 'box. These are similar to the GKN overdrives for defender LT230's, but a little smaller. I was only going to use mine when cruising on the flat, but then, with all that torque and towing a camper, I might just want to USE it.... And I can see THAT destructing too. Just face it. The Isuzu with a turbo on it will destroy most LR boxes except a TRLT95, so we just have to run 33" tyres minimum and stay under 130km/hr


JC

JC - you are probably right - I know very little about rover cars, only that a few models have landie diffs - I thought the SD1 was one of them... Must have been wrong.

I didnt say stick with rover diffs....

about the quickest ratio I know of in a diff is about 2.6:1 but its not all that tough. and I wouldnt put one in...

that said Im not into speed and Id be going the other way running 4.7:1 and just taking my sweet time since my plan to liver forever is thus far right on track I reckon I can afford to slow down.

__________________
Dave

"In a Landrover the other vehicle is your crumple zone."

Fozzy, 2.25D SIII Ex DCA Ute
The midlife crisis car
Some D1

For spelling call Rogets, for mechanicing call me.

So, has anyone actually tried putting an overdrive behind an Isuzu. Or are these only opinions. (well informed opinions I believe)

__________________
Reg....1985 110 County 3.9 Isuzu (Rebirthing)
Roy....1975 SIII LWB 2.25 Petrol
Suzi...1986 110 County 3.9 Isuzu

If I might offer my two bobs worth: try an overdrive behind an Isuzu and see how it goes. I have heard a lot of theories about the longevity or otherwise of various Landrover transmissions behind Isuzus eg an R380 won't last the distance - yet when I speak to people who are driving vehicles with the various transmissions fitted I find out that they have not had significant problems. So try an overdrive - in good condition - drive with a bit of mechanical sympathy and we might all be surprised at how long it lasts.

MyR380 seems to handling a 4BD1T without any problems (over 20000ks now - heaving towing - long distance fully loaded) - the torque rating of the box is significantly above the torque output of the engine.

Christopher

FWIW

the thing that lets the suzi eat a gearbox is its torque impulse at or near idle especially if loaded up and "chugging"

the rapid acceleration and deceleration of the shafts makes the helical cut gears change thrust loadings significantly which is sort of the equivelent of using a jack hammer on your bearings over time. If Ive still got them the piccy's of the dead box from brian hejlms county (lt85) provide a perfect illustration of this. I cut the front off of the fubar input shaft to make a clutch alignment tool but he might still have the bits and be able to take some more pics of exactly what turns to swarf behind the isuzu.

a short term solution to the problem is to up the idle speed of the suzi. of course a pure square cut box would be my long term solution, no thrust loading of the shafts then. (just woefull tooth contact to worry about)

__________________
Dave

"In a Landrover the other vehicle is your crumple zone."

Fozzy, 2.25D SIII Ex DCA Ute
The midlife crisis car
Some D1

For spelling call Rogets, for mechanicing call me.

The way i drive, it (the overdrive) would only be engaged in 4th gear at highway speed to reduce rpm and noise. Be nice to have a conversation without yelling.

__________________
Reg....1985 110 County 3.9 Isuzu (Rebirthing)
Roy....1975 SIII LWB 2.25 Petrol
Suzi...1986 110 County 3.9 Isuzu

not quite...

those bolt in overdrives are always engaged, they replace the input gear that slides onto the output shaft of the gearbox if the bolt in overdrive has a catclysmic failure unless youve still got your origingal drive gear (and the OD hasnt taken out what I call the idler gearset) you aint going nowhere.

they usually whine and howl like a banshee before they let go so you do get a wrnaing.

__________________
Dave

"In a Landrover the other vehicle is your crumple zone."

Fozzy, 2.25D SIII Ex DCA Ute
The midlife crisis car
Some D1

For spelling call Rogets, for mechanicing call me.

Dave

Thanks for your comments - it seems to that the major issue is allowing the engine revs to drop down too far - easy to do given the way the Isuzu pulls at low revs - keep the revs up a bit say above 1500 in the intermediate gears, and above 18-1900 in fifth and gearbox life should be reasonable

Christopher