Transfer Box Ratio's

[smo]

Has anyone got or driven a TD5 which has a transfer box running a 1.003 high-ratio??

Views/opinions please :)

[Budgie]

If you've got the 1.41:1 ratio box in the TD5 now then you're looking at a 29% drop in the final drive gearing.  :shock:

Even on 205R16 tyres this may lead to the vehicle being hard to pull away, you'll be in 2nd or 3rd gear to hold 30mph, any uphill incline will require dropping down one, maybe two, gears but you'll do less revs on the flat for cruising (if you can get there in the first place).
Mind you, I could have the maths all wrong, someone'll tell us if I am.  

The low range will be unchanged as they are the same across the board, only the high ratio differs.  

If you're looking for better cruising cos the engine is screaming on the motorways then, IMHO, you'd be better going for the 1.22:1 transfer box out of a Discovery with only 18% gearing drop.  

[smo]

You are corect about the % drop.

I had a 1.222Q geard transfer box on my last defender but it didnt make all that much difference on motorways etc. which i do a fair bit of.

I've done some calcs based on the formula MPH per 1000 RPM = 2.976D/MTR

D is tyre diameter
M is gear
T is transfer ratio
R is diff ratio

1st 1.003 = 7.39
5th 1.003 = 34.538
1st 1.222 = 6.063
5th 1.222 = 28.349
1st 1.140 = 5.255
5th 1.410 = 24.569

So @ 1000RPM using a 1.003 ratio instead of the standard 1.410 i would be travelling 10mph faster :)

I dont intend on doing this with the standard 122bhp output - itll be approx 175bhp to start with incresing to 200+ in the distant future :)

[Budgie]

Are you keeping the standard diameter tyres on it?

You could go for the 1.22 transfer box and a large diameter tyre to give you better speed & a bit of flexability for the future?  

I don't honestly know what it would be like with the 1.003 ratio in it but my feeling is that, for anything other than flat motorways, it'll be too low geared, even with the extra BHP and you'll be up & down the box all the time around towns.

I went the other way, I had the standard 1.22 box in the Disco and put 33" dia tyres on it meaning that it was hard to pull away etc & that's with uprated intercooler and injector pump. Then I changing to a 1.41 TD5 box & everything in the worlld was good again!!   :D

[Xtremeteam]

sorry to jump in but i "think" ive got a 1.66 Tbox in my 90 at the moment & with the 200TDi fitted it only does 65 mph ish comfortably,any more & im <trade term>revving the nuts off it <trade term> even with 750's fitted,just got a 1.22 Tbox 2 night that im gonna fit can you work out how much of a benifit ill get?

[Budgie]

According to my calculations (Ashcroft's Site) you'll have a 36.41% raise in the overall gearing.  

[Xtremeteam]

According to my calculations (Ashcroft's Site) you'll have a 36.41% raise in the overall gearing.  

will this cure the problem of "missing a gear" when im running on the motorway?

[Budgie]

Should do the trick Mikee, you'll notice that it'll be slower to pull away than it is now but you'll get used to it and it should give you better mpg into the bargin.  

[Xtremeteam]

Should do the trick Mikee, you'll notice that it'll be slower to pull away than it is now but you'll get used to it and it should give you better mpg into the bargin.  

oh well,better get used to not smoking boyracer with the 1.22 fitted although a big intercooler & pump adjustments will help  :twisted:

[smo]

will this cure the problem of "missing a gear" when im running on the motorway?

Yes.

I have every intention of upgrading the engine to put out a fair bit more power, meaning i can still smoke boy racers...and if i cant smoke em i can just scare them silly by being much bigger and pushy with it :p

My old Landy was a 110, i had the 1.22Q gears and upgraded intercooler and chip on that and it went like stink! :D