upgrade 300tdi defender gearbox with disco?

**cameron** · 4th January 2007, 11:09 PM

Hi guys,
I remember seeing threads in here (but I cannot find them for the life of me) regarding upgrading a defender gearbox with a disco gearbox in order to get a better top speed.

I am not really looking to change to an auto if that was what is recommended - can anyone either give me the good oil on this directly or pass me over to some established links so I can check out some old threads?

Cheers,
Cameron

**langy** · 5th January 2007, 02:16 AM

The answer is in the transfer case: disco's are 1.22:1, Defenders are 1.41:1. Swapping the gear clusters lets you go a bit faster, but less pulling power.

This is a website with a comparision of gearboxs and tc combinations

http://www.expeditionlandrover.info/gear_ratio.htm

**Bush65** · 5th January 2007, 08:57 AM

I haven't had anything to do with Defenders, so real experience from 300Tdi Defender owners may be different.

You need to know the pros and cons before doing this.

Defenders have larger diam tyres, and poorer aerodynamics compared to discos. Which is probably the main reason for the lower gearing in the transfer case.

IMHO, if you fit the disco transfer case, with the larger dia tyres, you will end up driving mostly in 4th gear, where you use 5th now.

However, if you find, when in 5th gear, you continually feel that you want to change into another higher gear, then the change may be worthwhile.

I fitted a defender transfer case to my rangie to compensate for larger tyres (just a little larger than defenders) and it performed much better. I could make better use of 5th gear on the highway.

In my 300Tdi disco, I have changed the diff ratio, for the same reason.

**zwitter** · 6th January 2007, 08:04 AM

Hi
I just installed the transfer case from a Disco with 1.211 gears in to a deafender 130 wit 300tdi. I also installed the dieselgas system and 2 lots of sound deadning at the same time.

Pros
I can cruise at 110k and still have a conversation. @2600rpm
As the disco box i bought had the Q gears it made one less gear whine.
Not in 5th all the time.
Could keep up with highway traffic with out the engine wanting to part company.
The stereo can be heard.
Nicer to drive.
theoreticaly better fuel economy
low range is not affected.

Cons
Hill starts are harder. With heavy trailer would need to do the low range start on anything other than flat ground. This would apply to standard gears too. Just done 2000k with camper trailer @ 680Kg and another 300Kg in back plus 4 people and was fine but a little more clutch required to get going. Once the turbo kicks in it is fine.

I can now hear the rear diff whine / drone.

I am not sure the dieselgas is tuned properly yet. It only got installed the week before christmas. going in soon to be checked/tuned

I kept the old TX box incase. Would I change back? No probably not unless doing heavy towing all the time.

The gears can be bought in UK for 255pounds plus import duty, GST etc then need to be installed and preloads etc done probably best with box out.

You need to get the right box with the central diff and diff lock, late Disco 1s I think. I picked up whole 2001 Disco 1 TX box with 51000k on it for $800 locally and $650 to install. (KLR) The rear (?) housing needed to be swapped for the speedo drive. And handbrake as the cable is different!

Tusker I think has the same mod in a 110

if you are local pm me and you can have a drive.

james

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upgrade 300tdi defender gearbox with disco?

Just did it on a 130

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