GKN Versus Rocky Mountain Overdrive

[western]

but the same engine will still be turning at 3000rpm at 65/70 whereas with a OD inline it'll be doing 600 to 800rpm less therby saving more fuel.

[FridgeFreezer]

but the same engine will still be turning at 3000rpm at 65/70 whereas with a OD inline it'll be doing 600 to 800rpm less therby saving more fuel.

Not if he fits a Disco/RR transfer box, which should set you back all of £50-£100 in good condition and has better parts availability than either flavour of OD.

[reb78]

Not if he fits a Disco/RR transfer box, which should set you back all of £50-£100 in good condition and has better parts availability than either flavour of OD.

Splitting hairs a little, but the OD raises gearing 28%, the disco box 15%, so the revs will still be lower in 5th (on a 1.4:1 TXB) + OD than in 5th on a diso transfer box. My mums TD5 disco could do with an extra gear in top for motorways, so i'd still opt for the OD on a defender WITH a well serviced engine. I can understand why parts might be a worry for the ODs though (devon 4x4 do seem to have a good stock of everything for the GKNs and can source all of the spares from the states apparently).

[Philip Tonkin]

What about a Defender with both Disco 230Q gears and an OD?

[western]

What about a Defender with both Disco 230Q gears and an OD?

probably be way over geared & virtually undriveable.

the 1.22 TB ratio gives a 15% change & the OD gives around 28% with both fitted your looking at a 42 to 45% change

[101sean]

I'm still pleased with my OD, I'm comitted anyway and it suits where and how I drive. When the OD played up I did wonder whether I'd done the right not fitting a Disco box and an ECU retune but not sure it would have worked well in my circumstances. There's merits in both (ecu may still happen though ).

Doing it now, I'd probably fit the RM one if they were easy to get! Used to that style of OD in a series I used to own and have a Rangie OD in the 101 which is interesting with cable operation (and withstands a lot of abuse)

Gaining MPG was never a good reason for an OD, more comfortable cruising (for driver and engine) is the main benefit.

[FridgeFreezer]

Splitting hairs a little, but the OD raises gearing 28%, the disco box 15%

Fit a 1.003:1 box from an early Range Rover then or add some bigger tyres.

[Modchop]

I had a GKN OD fitted to my previous 110 (Td5) and it was fantastic with no problems in the 2 and a half years I had it fitted. Changing the oil in it though was a messy business! I heard that GKN no longer provide any support for them now, though I'm not 100% sure on that.

In my current 110 (also a Td5) I've gone for the Disco gears in the transfer box. These have vastly improved it's 'cruising' manners on M-ways and A-roads, etc. It's a little slower off the mark, but if you want to take part in 'traffic grand prix' you wouldn't buy a Defender would you.

Cheers.

[western]

I heard that GKN no longer provide any support for them now, though I'm not 100% sure on that

correct, all the spares/rights have been taken on by Devon4x4, V8 Freak had his GKN unit rebuilt by D4x4 & they did a super job.