300tdi transfer box

[paime]

A friend of mine has inherited a Discovery 300tdi transfer box, would this be worth fitting to my 90 TD5 to give me a bit more legs in 5th gear? I'm aware that there is a conversion to be done which helps out Defenders in 5th but i can't remember if it's a disco TD5 box that's required or whether a 300tdi transfer will work.

[Chicken Drumstick]

Assuming it is a stock Disco 300Tdi box it will have the taller 1.2:1 high range gearing. This will raise all of your gears, as well as give you better cruising rpms. The downside is, it may blunt performance in terms of acceleration and may make it feel less peppy. Really depends on your driving style and the types of roads you will be on, to how much impact this will have. For motorway/dual carriage the taller gearing makes sense. For B-roads and country lanes less so.

What size tyres are you running at the moment? 

[paime]

I've got Grabber AT3s 235/85/16 on steel modulars. I do a mix of town and dual carriageway stuff and the noise at 70mph makes me sad.

If i go down this route, will i need to modify anything to make it fit/work or is just a case of swapping over the handbrake mechanism and off i go?

 

Edited December 13, 2019 by paime

[cackshifter]

If you tow more than occasionally it may be a bridge too far, you'd definitely need to practise your low to high range changes on the move. But it is not a massive job to switch and try out. Solo, I think it would be fine unless you carry a lot of weight

[Ed Poore]

I've been running a 1.2 transfer box in my 110 for the last 8 years or so and wouldn't go back (265/75R16 tyres so similar rolling diameter to you). I've done plenty of towing with it and still wouldn't go back, in fact apart from pulling away with 3.5 tonnes on a hill I'd say that the 1.2 box suits towing at 60mph you're comfortably into 4th gear and in the power band so 5th can effectively be an overdrive in that situation.

Earlier in the year I was towing 3.5 tonnes quite regularly and was considering either a VNT or dropping back to a 1.4 and potentially sourcing an overdrive. However, after the second crank snapped and I built up another engine (which the bottom half I'd sourced had had the fuel pump tweaked slightly) then that's again transformed the vehicle. I'd say with the relatively easy tuning options available on a Td5 then go for it.

In fact a friend who has a 2.4 Tdci station wagon 110 commented on a recent trip to the Highlands that mine was a lot quieter than his. There's a bit more sound proofing in mine but there are some gaping holes in the bottom of the doors. This was on mud terrains but we were cruising at 60mph due to towing an Argocat up. We actually worked out that all the 6 speed does in the Tdci Defenders is introduce a lower first gear and run a 1.2 transfer box. The Tdci's 6th gear is equivalent to an R380's 5th.

Picking up on Chicken Drumstick's comments I'd actually say that the gearing is better set up for country roads and if you want to get a shift on. On a 300Tdi 2nd year tops out at ~30mph, 3rd at 50mph, 4th at 65ish and 5th depends on wind conditions as usual... I've generally found the slightly taller gearing, with the exception of first, puts the the gears in a nicer location.

I will admit to having to slip the clutch quite a lot in first but after 70k when I swapped out the first engine earlier this year the clutch was hardly worn at all (had fitted a 130 clutch when I changed it at about 100k from the original clutch). 

[Chicken Drumstick]

3 hours ago, cackshifter said:

If you tow more than occasionally it may be a bridge too far, you'd definitely need to practise your low to high range changes on the move. But it is not a massive job to switch and try out. Solo, I think it would be fine unless you carry a lot of weight

Eh?????

[Chicken Drumstick]

10 hours ago, paime said:

I've got Grabber AT3s 235/85/16 on steel modulars. I do a mix of town and dual carriageway stuff and the noise at 70mph makes me sad.

If i go down this route, will i need to modify anything to make it fit/work or is just a case of swapping over the handbrake mechanism and off i go?

 

Should be ok with those tyres. As you can run that size on a D1/RRC. Pulling away in 1st requires more slip and you’ll find you probably need 3rd gear for 30mph rather than 4th unless on the level. 

[Mo Murphy]

My penny's worth. 

The TD5 in standard form is not a million miles from the preceding Tdi.

On a bog standard Tdi engine I found that the gearing is too high with 235 tyres for anything other than motorway work with 2nd and 3rd gear ratios in particular in the wrong place for comfortable progressive driving.

I tried it and I felt it was awful.

On a Tdi mildly tuned with big intercooler, increased boost and fuelling mods it is a wonderful thing that let's you take advantage of the extra power and still return decent fuel economy.

I tried it and left it fitted. I find now that I drive with just the first third of the throttle now which, in conjunction with the taller gearing has done wonders for my fuel economy.

I don't tow anything so I don't know how it would fare under those circumstances. 

Ed's barge goes very well with the 1.2 transfer box, once the black smoke has cleared you can see how much progress he can make ! 😉

So if yours is standard I wouldn't recommend it. 

But if it is tweaked it could make things a whole lot quieter, more refined and generally more pleasant.

HTH

Mo

 

[Ed Poore]

1 minute ago, Mo Murphy said:

Ed's barge goes very well with the 1.2 transfer box, once the black smoke has cleared you can see how much progress he can make ! 😉

It's my built in smoke screen. 

Should turn it back a bit, but you know, laziness and all that. Got a few months yet before the next MoT, be nice it it doesn't take a few attempts to get through on emissions.

[Bigj66]

I did the same conversion to my TD5 110 which is tuned to around 160hp. You can feel the increase in gearing compared to standard but as I don’t tow or carry any heavy kit regularly, I find the higher gearing better for motorway work without noticing any real difference in about town driving. Engine noise is reduced a bit at higher speeds but I also removed the straight through exhaust on mine at the same time the T-box was changed so difficult to tell which one made the greater difference.

Not sure how it would be with a standard tune engine though. I’m also on 235s.

[Landrovernuts]

I also have a 1.22 transfer box in my 110 TD5 double cab and agree with above that it is one of the best things I have done to it. I tow with mine and it pulls 5th gear easy. The only time I need low range is when pulling away with a loaded trailer on a steep hill, but then that is what low ratio is for. It is much quieter on the motorway and sometimes when not pulling a trailer, I find that i could do with another gear! As for being chipped - my engine is chipped but I have no idea to what level and would say would be good in a 90 even if it is not chipped as it is lighter although still has the barn door aerodynamics.

Toby

[Ed Poore]

4 hours ago, Bigj66 said:

Not sure how it would be with a standard tune engine though.

I've only had a tweaked engine since Easter and had a bog standard 180k 300Tdi in it prior to that and it was fine. It's was no speed demon but then most Defenders aren't either. It felt a little under-powered sometimes - notably when I used to tow the Hampshire Air Ambulance's helicopter but then I could drop down into 4th and sit at 50-60mph rather than continually changing between 4th and 5th. In all honesty I'd have probably left it like that had I not started snapping cranks. There were only two times I had to drop down into low range and both were towing 3.5 tonnes. One was pulling out of a field at my parents with a trailer full of sheep to take to the market. The second was towing an L322 on a trailer through some back-roads in Carmarthenshire which were full of switch-backs, hairpins and 1 in 3 hills. Was much nicer to stay in low range since I wouldn't have been able to do much above 25mph anyway.

I acquired a 4.6 P38 after the second crank to see me through until I moved house down to Wales and was actually seriously contemplating dropping that into the Defender. Then a bottom half came up for sale on here and unbeknownst to me it has been tweaked previously. It was such a transformation that the 4.6 idea died very quickly.

If I was always towing through Mid Wales with 3.5 tonnes behind the Land Rover then I wouldn't change the 1.4 box. However in pretty much all other scenarios I'd stay with the 1.2.

[Tobias]

on a 300tdi you need to swap out the speedo drive gear in the LT230. The disco square hole is smaller. If the same applies to a TD5,  don't know. Test your speed sender in the hole before you put the box in. It is possible to change with the box in place, but much much easier on the floor.

 

T

[paime]

So essentially it's a good thing to do but only if i apply some tuning to the engine? 

[Ed Poore]

It depends on how you drive really. If you're pretty laid back and just potter around I'd do it anyway. If you demand the most out of the engine, well why you driving a Defender then? 

I had it in standard tune for years and due to the reduced revs at higher speeds I lived with it. It was a little lack-luster at the bottom end but really only marginally got on my nerves when I was towing a lot and even then not enough to warrant going back. Had the latest engine not been tweaked for me I doubt I'd have done it myself but because it was already done for me I realise now I should have done it a long time ago.

[paime]

I mostly just potter around town and then out to the in-laws which involves some dual carriageway stuff and some 60mph driving. I would like to take it on longer runs at 70mph as well but it's just far too noisy hence my thinking to use the 1.211 transfer i've managed to acquire. I think i'll wait until i've done the intercooler and had the turbo rebuilt before swapping it out. Sounds like everyone has improved their engines in some way before doing it so i'll follow suit.

[Ed Poore]

???

Didn't you read my posts? Out of the last 8 years I've been running a 1.2 box it's only been the last 6 months that I've had a tweaked engine? Was perfectly happy with it before BUT having now got a tweaked engine it's much better. So I wouldn't worry about the engine side of things if you've already got the transfer box lying around.

Bearing in mind all mine has had is a tweak to the pump, no change to turbo and/or intercooler.

[Chicken Drumstick]

On 12/16/2019 at 1:03 PM, paime said:

So essentially it's a good thing to do but only if i apply some tuning to the engine? 

It is completely subjective. What will be right for one person, will not be for another. I would say, while the transfer box will lower cruising rpm, don't expect miracle on how much sound this will reduce. The rpm of the engine is only one of many things that contribute the noise you hear when going down the road.

It is probably also worth noting that there are other options, you could get an OD like a Roamerdrive. Bit pricey but arguably a better solution. Or if you have your gearbox rebuilt you can replace the 5th gear with a taller ratio, thus retain the same performance in the remaining 4 gears.

[dailysleaze]

Around town, it makes it easier to accelerate into traffic gaps on a roundabout but hill starts require more clutch slip.

Overall my 1.2 Box change has been positive.

[paime]

Thanks all, plenty to ponder. A friend has the 1.2 in his 300tdi, will driving that give me a good insight into how it would feel in a TD5 or is the difference in engines too much to make them comparable?

On 12/17/2019 at 9:25 AM, Ed Poore said:

???

Didn't you read my posts? Out of the last 8 years I've been running a 1.2 box it's only been the last 6 months that I've had a tweaked engine? Was perfectly happy with it before BUT having now got a tweaked engine it's much better. So I wouldn't worry about the engine side of things if you've already got the transfer box lying around.

Bearing in mind all mine has had is a tweak to the pump, no change to turbo and/or intercooler.

My turbo is a bit shoogly (technical term) and my intercooler is full of gunk and collapsing in on itself so i'll need to replace them but only back to stock, i'm not going to upgrade in the pursuit of more bhp. Your post said you "lived with it" so i sensed some frustration with the standard level of tuning in a TD5 when mated to a 1.2 transfer box?

[Chicken Drumstick]

Can't understand replacing the stock intercooler with another stock one myself. A bigger intercooler is nothing but positive on every front.

[Ed Poore]

1 hour ago, paime said:

so i sensed some frustration with the standard level of tuning in a TD5 when mated to a 1.2 transfer box?

Not really, "lived with it" was probably with hindsight. The tweaked engine has utterly transformed things but I was more than happy with the performance beforehand, it was just a little more sedate than with a 1.4 box.

To me the biggest "unforeseen" benefit is not actually the taller gears for cruising but I feel it actually puts the gears into a much more useful range. To try and explain this what I mean is that if you wanted to sit at the respective speed limits (e.g. 30, 40, 50, 60, 70) I'd always be changing between two gears depending on inclines etc. With the 1.2 box then basically 2nd is still usable up to 30mph but you wouldn't want to sit there for long (so useful for steep hills and cornering), 3rd is where the power band is so used most of the time unless pottering along and then 4th and 5th become an overdrive to knock the revs right down. As you go up above 30 you basically lose 2nd gear and 4th becomes your main gear to stay in the power band. I can cruise along at 60mph all day long in 4th if I wanted to - which you wouldn't do with a 1.4 box, it (4th) is still usable up to 70mph if you really need it. One tangible benefit is that if you're towing on main roads then you can stay quite comfortably in 4th which is a straight through and therefore the strongest gear. The difference the tweaked engine has allowed is that whereas I would have to change down a gear for climbs or if towing then I can now just stay in the same gear. The only significant downside is that first is quite tall now.

As you can probably guess I'm a bit fan of the 1.2 box with or without engine tweaks. I would say that if your engine is not in fine fettle (on a standard tune) then it might not be the best idea, but provided the engine is running well then I would recommend it. Tweaking the engine only makes things even better.

Perhaps the best bit of advice I can give is if you wanted to try it out without actually fitting the different transfer box then try driving around and never use first gear, not even for hill starts, towing or maneuvering. If you can live with that then I'd say that you're reasonably close to what driving a 1.2 box would be like except without the extra gear up top.

[Mo Murphy]

You could just fit it and try it paime, its a mornings work.

If you don't like it you can change it back.

Cost is 2 oil fills.

Mo

[paime]

17 hours ago, Mo Murphy said:

You could just fit it and try it paime, its a mornings work.

If you don't like it you can change it back.

Cost is 2 oil fills.

Mo

Didn't realise it was a morning's work so i reckon that's the best approach. Worst case scenario i can always swap back. Is it straight forward enough to swap them over or will i need adaptor plates and the strength of 10 men to wrangle it into place?

[Ed Poore]

12 minutes ago, paime said:

or will i need adaptor plates and the strength of 10 men to wrangle it into place?

Depends on how strong your men are... It is pretty straight-forward to swap but don't underestimate the amount of time the first time you do it. If you need the vehicle I'd set aside a weekend for it the first time around if doing it solo.

I've done it all manner of ways but the last time I was on my own effectively on the side of the road (at my old home). I actually put two small ladders on the outside of the front doors and tied them to the chassis rail. Then I put a 4x4 fence post through the windows, this gave me a beam which I could then attach a small pulley block and that meant I could lift and support the weight of the transfer box with the pulley block which, once tied off to the rear seat frame (could probably go out the back door to the tow bar if you needed to) meant I had both hands free to maneuver the transfer box into the correct position.

With the help of someone who's done it before I've done it in well under an hour. Mind you we've both got well versed in it (and engine swaps, the last one done solo was 6h ).