Transfer box ratios

[Junglie]

Hi all.

So. Yes, I'm going ahead with the swap out of my 2.5NA and swap in with a 3.9 V8. Because, well because.

I need to overhaul my transfer box anyway because it's making horrible noises, and i'm guessing that the ratio is going to be wildly out. Or is it? 

Big question is this. I suspect that I'll need to replace the main pinion with a cross drilled item to give the main shaft an easier life. Can I adjust the ratio by just changing that, or is it way more complicated? If I can just get away with that one, can anyone give me a clue as to the number of teeth I need to get?

Cheers,

Simon

[western]

Have a read of this info Ashcroft Transmission LT230 transfer boxes

[Junglie]

Brilliant, thanks

[FridgeFreezer]

If you're going to a 3.9 in a van-body 110 you can drop in a 1.222:1 ratio from any RRC/Disco 1, they're ten a penny, maybe £50-100 used depending on how oily they are. The 3.9 will pull it happily and it will cruise lovely on the motorway.

If your LT230 is 1.6 ratio they're rarer and more valuable to the boys who fit silly big tyres so don't part with it, although it's more likely to be standard Defender 1.4:1 ratio.

[landroversforever]

On 1/3/2021 at 11:18 PM, FridgeFreezer said:

If you're going to a 3.9 in a van-body 110 you can drop in a 1.222:1 ratio from any RRC/Disco 1, they're ten a penny, maybe £50-100 used depending on how oily they are. The 3.9 will pull it happily and it will cruise lovely on the motorway.

If your LT230 is 1.6 ratio they're rarer and more valuable to the boys who fit silly big tyres so don't part with it, although it's more likely to be standard Defender 1.4:1 ratio.

2.5 diesel will be the 1.6 IIRC. 

[landroversforever]

On 1/3/2021 at 8:38 PM, Junglie said:

Big question is this. I suspect that I'll need to replace the main pinion with a cross drilled item to give the main shaft an easier life. Can I adjust the ratio by just changing that, or is it way more complicated? If I can just get away with that one, can anyone give me a clue as to the number of teeth I need to get?

If you're rebuilding it and changing the ratio it will be a gear set change. Not just a change of the input gear. 

[mickeyw]

Agreed, a 2.5 NAD would have been built with a 1.6:1 box.

As Fridge has said, a 3.9 will happily pull a 1.22:1 transfer ratio behind a manual gearbox box in a 110. That is as long as your tyres are no bigger than say 33"

[FridgeFreezer]

12 minutes ago, mickeyw said:

Agreed, a 2.5 NAD would have been built with a 1.6:1 box.

As Fridge has said, a 3.9 will happily pull a 1.22:1 transfer ratio behind a manual gearbox box in a 110. That is as long as your tyres are no bigger than say 33"

If Junglie has a 1.6 ratio box he should have no trouble selling it then.

Mind you, maybe just pull the whole engine + box + transfer box out as one assembly and store it and then plop a 3.9 + box + transfer back in as you're going to need either a V8 conversion plate or a different gearbox anyway.

Personally if you've got the money I like the idea of dropping an LT77 or R380 box in that's built for a V8 Defender, that way everything is pretty much as the factory intended, you can use standard V8 Defender bits like mounts, hoses, rad, etc. in standard positions for easier parts/servicing.

[Junglie]

Thanks everyone. 

I came across a V8 LT77 box cheap, and as I'd already bought the overhaul kit for my existing box (both the same generation, happily) I will use it on this box before fitting it.

If I can find a 1.22:1 transfer box for sensible money then I'll get that as well, otherwise I fear I'll have to either live with the existing one for the moment (presumably I'll be able to rip the white lines off the road but will run out of revs at about 60?) or do a rebuild and change the gearset. If anyone has a 1.22 unit lying around that they'd like to swap then let me know...

Cheers,

Simon

[FridgeFreezer]

Make sure it's a Defender gearbox with the gear shift linkage coming forwards, otherwise the gearstick wants to come up through the middle of the cubby box. Ashcroft do relocation kits these days I think.

[Bowie69]

31 minutes ago, Junglie said:

(presumably I'll be able to rip the white lines off the road but will run out of revs at about 60?)

Depends on the tyre size, if you are on 35s, with a 1.6 tcase, then it works out about stock....

On 32s, you'll do 80mph, but be doing 4000rpm...

Been mentioned a few times, what tyres are you running?

[Junglie]

49 minutes ago, Bowie69 said:

Depends on the tyre size, if you are on 35s, with a 1.6 tcase, then it works out about stock....

On 32s, you'll do 80mph, but be doing 4000rpm...

Been mentioned a few times, what tyres are you running?

At the risk of appearing stupid...I honestly have no idea. Whatever goes on standard rims. I never looked when I got it and it's dark and pissing with rain now so, um. 

[Bowie69]

Fairy snuff

[FridgeFreezer]

Junglie appears to be on 7.50R16's:

 

[Bowie69]

Aha, well, once you have the V8 in, you may want to think about changing the tyres for something that will actually allow you to put V8 power to the tarmac

No need to go bigger, but a more modern all terrain in 235/85 would probably suit (almost the same size as what you have), and be much safer, but up to you of course

A V8 would pull those tyres with a 1.2 box quite happily.

[Chicken Drumstick]

17 hours ago, mickeyw said:

Agreed, a 2.5 NAD would have been built with a 1.6:1 box.

As Fridge has said, a 3.9 will happily pull a 1.22:1 transfer ratio behind a manual gearbox box in a 110. That is as long as your tyres are no bigger than say 33"

I thought only the 110's had the 1.6 or did the 90s too?

[FridgeFreezer]

29 minutes ago, Chicken Drumstick said:

I thought only the 110's had the 1.6 or did the 90s too?

Junglie has a 110, that's what's being discussed here.

[Chicken Drumstick]

13 hours ago, Junglie said:

Thanks everyone. 

I came across a V8 LT77 box cheap, and as I'd already bought the overhaul kit for my existing box (both the same generation, happily) I will use it on this box before fitting it.

If I can find a 1.22:1 transfer box for sensible money then I'll get that as well, otherwise I fear I'll have to either live with the existing one for the moment (presumably I'll be able to rip the white lines off the road but will run out of revs at about 60?) or do a rebuild and change the gearset. If anyone has a 1.22 unit lying around that they'd like to swap then let me know...

Cheers,

Simon

Re: the transfer box.

 

I think it comes down to what you want from the vehicle. IMO lots of people over gear the V8's. Now don't get me wrong, the V8 makes a shed load more grunt down low than a 2.5 petrol. But the V8 still does its best work at mid rpm or higher (especially with a sensible cam swap).

We've just put a 3.9 EFI into a factory 3.5 90. It has slightly different gearing with the LT-85 5 speed and also uses a super tall transfer box 1.192:1 (35D). the 3.9 will pull it fine, well the 3.5 did, but the 3.9 is so much better

It will pull 5th gear at 25-30mph quite happily. But I would say, it doesn't exactly feel zingy..... It always has plenty of power. But 3rd gear takes you well over 70mph and you don't really get to enjoy the V8 revs as much as you may think. My opinion is, shorter overall gearing would totally transform the character of the vehicle and make it more enjoyable to drive. But might not be too everyones tastes. In this particular example, swapping in some 4.10:1 diffs is likely the answer, as we have a pair sitting under the workbench.

 

But with an LT-77 and 3.:54 diffs. I personally think a 1.6:1 would be the most fun transfer box option, but for cruising you would need to budget for an Over Drive such as a Roamer Drive. As the 1.6:1 would feel like the V8 is screaming its nuts off in 5th!

The standard 1.4:1 transfer box would be the compromise between performance and cruising without the need for an over drive. The 1.2:1 from a Disco would I expect be very similar to our setup. Which while perfectly fine, has a somewhat lazy feel about the performance.

 

I also have a 3.9 V8 in a Triumph TR7, although this runs a 4 brl carb rather than EFI. But it has very short gearing and is simply loads of fun, as long as you aren't on a motorway. It really does need an extra gear.

 

In terms of the V8's I've always found in stock trim, the serpentine 3.9's rev a lot better than the earlier vee belt ones. Not entirely sure why. Either way, RV8's are know to wear cams and lifters, so it may well be worth also budgeting to refresh these. As worn ones will make them breathless a higher rpms and potentially be down 20hp +- A mild cam upgrade really wakes them up in the higher rpm and shouldn't sacrifice low end torque.

 

Ultimately I feel it is very much a balancing act between the character of the engine and how the gearing effects this. Your personal driving style will also have a big bearing on this too. I don't have the 3.9 V8 90 on video, but it is worth noting that it is "comparatively" hard work to rev it out in the gears, as the gears are long. And out having fun will likely only result in 1 or 2 gear shifts.

On the flip side, my TR7 with silly short gearing is very easy to rev out to the red line and rips through the gears. This is it, albeit with a cammed 3.5 (before the 3.9 went in), but with the same gearing. I think a similar character in a 90/110 would be pretty awesome!

 

 

[Snagger]

Overdrives only fit the 1.4 LT230s.

[Chicken Drumstick]

1 hour ago, Snagger said:

Overdrives only fit the 1.4 LT230s.

Didn't realise this. Assume this is for all over drives not just the Roamer Drive? Bit of a shame.

[Landrovernuts]

I have to agree with Chicken drumstick here, I have had two V8 90's both were tuned with one having a 3.5 (Boxer set up) and the other a V8 developments 4.3 EFI engine (Raised compression, stage 3 heads, H218 camshaft and remapped). They both had 265 tyres and 1.22 TBoxes (original was 1.192 27D on V8 90's)  (and LT85 gearboxes) and while they were good on the motorway 5th gear was just an overdrive cog and not much use for anything else even with the 4.3. I remember having to change transfer boxes and fitted a spare 1.4 which made a hell of a difference in that it felt bloody quick, put a big smile on my face and was actually slightly better on fuel. Cruising on the motorway was not bad either and not actually not that far off my RRC (1990). 

If it were me again, I would fit a 1.4 TBox especially in a 110 but realise it is down to preference and what you will use it for. You can put the figures into the Ashcroft calculator and see what works best for you.

Toby

[Bowie69]

All depends on what size tyre you run too.... a 1.4 tcase on 33s feels about right in my RRC.

[mickeyw]

My old 90 was a factory V8, so 3.5 carb engine with a LT85 and 1.192 transfer ratio. Bear in mind that most 90s left the factory with little 205 tyres, so could easily handle this gearing. The 750R16s I was running also managed OK
After that trf box died the cheapest option was a used 1.22:1 unit.

Later on I upgraded to a 3.9, and later still a ZF auto box and 33" tall tyres (255/85R16). The 1.22 ratio was absolutely dreadful with the auto as it was too highly geared. It never got into top on general back roads driving speeds. On motorways it would cruise OK comfortably until you got to a hill. It wouldn't kick down of it's own accord unless you floored it, and pulling down to 3rd (manually) resulted in it revving way too high, yet in top it had no pull. Changing to a 1.4:1 totally transformed the drive and actually improved fuel economy!

50th anniversary V8 90s left the factory with the 1.22:1 transfer ratio in the 'interests of economy' but many owners changed to a 1.4:1 box as they felt it was too sluggish. Remember that the 50th had 265/75R16 tyres (~31" tall) as standard.

i think someone above mentioned Ashcroft's tyre size and gearing calculator. I highly recommend it to help you understand where your gearing needs to be.

[Snagger]

14 hours ago, Chicken Drumstick said:

Didn't realise this. Assume this is for all over drives not just the Roamer Drive? Bit of a shame.

Yes, GKN only fits the 1.4 and I think the same is true of the commercially available underdrives too - they were all generally intended for Defenders, not Discovery’s or RRC.

 

Having been in a vaguely similar position with my 109, using a standard SIII transmission with overdrive and finding it under geared on the 4.71 diffs and trying the 3.54s, I strongly agree with the couple of comments above that it is far better to to be under geared than over geared - within reasonable bounds, both will have similar fuel consumption, but the under geared vehicle will be far easier to drive and will be far more reliable, wearing or breaking transmission parts far less than the over geared one, and not needing to slip the clutch as much.  Driving around town or in hilly areas is horrible with an over geared vehicle, and can even be a bit dangerous at junctions.

I can see the argument for fitting higher than standard transfer cases like putting a 1.2 into a Defender or the Ashcroft HRTC into a Series vehicle, but having the standard unit and an overdrive is far superior, even though it introduces more moving parts and potentially more energy losses and reliability issues (the GKN seems the most problematic).  The flexibility of having standard gearing for most circumstances and being able to step up on the move is enormous, rather than living with a compromised transmission that struggles with accelerating, hills or towing and makes town driving a chore.

[Junglie]

Thanks chaps. Some really useful stuff there.

Looks like I'll be on the hunt for a 1.6 LT230 as well. Anyone got one knocking about?

I was warned about this. I seem to have been bitten by the Landy bug - what was going to be a cheap bit of fun is turning into a rather less cheap obsession...