can anyone help on gearing

Hi all
my discovery1 200tdi is just about to top 200,000 and the gearbox/ t box are on their way out. looking on ashcrofts site they say I should be getting 70 mph at 2500 revs, I'm only getting 60. While Im saving up the money for their fitted recons I'd like to find out why I'm undergeared. gear box and tbox have the correct serial numbers, can't find numbers on the axles to check them, tyres are 205/80 r16s so not the biggest but still a standard size. I guess I'll never know if the diffs are correct without getting them taken apart, but ashcrofts want all the money for that as well so is my only option to buy bigger wheels/tyres? or is their website optimistic. Must say its always seemed overly revvy/noisy on motorways.Any thoughts anyone? mike

check with a sat nav

tyres?

depends on speedo drive as well several choices

you can check diff ratio by jacking rear wheel up and with hand brake off mark prop and diff housing ,wheel and body,turn wheel once and count rotations of prop, 3.54 should be 1.3/4 turns,lrs arent accurate anyhow and as fanatic says numerous speedo gears for different tyre optoins,who knows whats been fitted,how much do ashcrofts charge for gearbox -transfer box change

Thanks for the pointer to the posting article and apologies for the sketchy post, i'll try to improve!

James you had the info I need, and I now see I could have got that without asking by looking harder! Many thanks for your patience.

FYI The speedo, tho making a frightening noise in cold weather as the cable shrinks away from the clock, is fairly accurate (just checked my notes and at steady 2500 revs the speedo says 58, satnav reads 55. at 3000 revs I'm getting 72 on the speedo and 68 on the satnav, a garmin zumo).

Until recently I had thought the engine had been badly abused due to the fact that there is so much noise and harshness between 3000 - 3500 revs. ( I had an early 110 some years ago and had a 2nd hand 200tdi professionally installed which was excellent) But now I think the gearbox may be the prime cause as there has been a grinding sort of harshness evident for some time as if bearings are giving up, and an increasing mechanical row from the gearbox when under load. If the gearing is wrong this will make everything worse so I need to sort it. I will check using James' info asap.

ashcrofts price for L77 gearbox and transfer box fitted was £1312 plus vat inc. clutch and bell housing. I think I worked out if i upgraded to r380 box and included clutch and transfer input gear it would end up at £1869 inc vat, and to include diffs as well would push it up to £2481!. they said they would include a couple of flange kits for the tbox for free (quoted £200 on their own by local L/R place who said they didn;t know how ashcroft did the fitting for the price).

As its my ideal work vehicle ( I'm a gardener /soft landscaper) I can't afford for it to be off the road for long and being very slow with the spanners, and having to park in a car park 50m from my door i usually end up paying for it to be done. Planning to give the engine to Turners ( Just down the road) when my lucky dip comes up, gearbox is first tho.

thanks again for replies guess I'll be speed-weeding for the extra cash!!

if i was you i would fit reco gearbox and new clutch ,get good second hand transfer box and diffs if needed,even engine ,unless engine is seriously tired you wont get the bits that need relacing ieturbo and injection pump and other ancillaries , i would bother going to r380 you wont notice the difference ,recon gear box are available for £400 clutch kit £60 borg and beck, fitting £300, a good used 300 tdi transfer box is more than adequate

marmike said:

Hi all
my discovery1 200tdi is just about to top 200,000 and the gearbox/ t box are on their way out. looking on ashcrofts site they say I should be getting 70 mph at 2500 revs, I'm only getting 60. While Im saving up the money for their fitted recons I'd like to find out why I'm undergeared. gear box and tbox have the correct serial numbers, can't find numbers on the axles to check them, tyres are 205/80 r16s so not the biggest but still a standard size. I guess I'll never know if the diffs are correct without getting them taken apart, but ashcrofts want all the money for that as well so is my only option to buy bigger wheels/tyres? or is their website optimistic. Must say its always seemed overly revvy/noisy on motorways.Any thoughts anyone? mike

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There are 2 main variants of the LT230 transfer box, the only difference is the high range gearing

Defender High Range: 1.41:1
Discovery High Range: 1.22:1
Coil Sprung Low Range: 3.32:1

Low range is the same on all of them.

The taller high range was used in the Discovery and the other in the Defender.

205 tyres were a standard size but quite small I think, so will offer up higher rpms for the same cruising speeds.

A 205/80R16 is a 28.91" tall tyre, my tyre cal says this tyre size with the 1.22:1 transfer box and a 0.83:1 5th gear and a 3.54:1 diffs should equal:

2000rpm = 48mph
2500rpm = 60mph
3000rpm = 72mph
3500rpm = 84mph

So I'd say it's 100% right what you are getting at present.


I haven't checked Ashcrofts site, but are you sure you are reading it right? With stock gearing I make it that you'd need a 34" tall tyre to achieve 70.6mph @ 2500rpm.

marmike said:

Hi all
my discovery1 200tdi is just about to top 200,000 and the gearbox/ t box are on their way out. looking on ashcrofts site they say I should be getting 70 mph at 2500 revs, I'm only getting 60. While Im saving up the money for their fitted recons I'd like to find out why I'm undergeared. gear box and tbox have the correct serial numbers, can't find numbers on the axles to check them, tyres are 205/80 r16s so not the biggest but still a standard size. I guess I'll never know if the diffs are correct without getting them taken apart, but ashcrofts want all the money for that as well so is my only option to buy bigger wheels/tyres? or is their website optimistic. Must say its always seemed overly revvy/noisy on motorways.Any thoughts anyone? mike

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Our first Disco was a TDi 200 manual like yours and ours did the same revs ie in 5th gear it would be doing just shy of 60mph at 2500rpm.

The later TDi 300/R380 combo will give 70mph at 2500rpm right enough.

We ran this car on 205/80/16's.

thebiglad said:

Our first Disco was a TDi 200 manual like yours and ours did the same revs ie in 5th gear it would be doing just shy of 60mph at 2500rpm.

The later TDi 300/R380 combo will give 70mph at 2500rpm right enough.

We ran this car on 205/80/16's.

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I think your speedo might be out tbh.

The R380 in a 300Tdi has a 0.77:1 5th gear whereas most LT-77's have an 0.83:1 5th.

This translates that the 300Tdi with 28.91" tyres (ie 205/80R16's) will be pulling 64.7mph @ 2500rpm not 70mph.

V8 300 Series Disco's with the R380 did have a taller 5th again at 0.73:1, if your Tdi has a V8 spec R380 then 2500rpm would be pretty close at 68.2mph

thanks james martin I have now checked the diff by your method and it would seem I have the correct diffs at 3.54. Also thanks for the sensible buying advice.

thanks thebiglad & 300bhp/ton for the helpful background info which would seem that the 3 of us are right and ashcrofts being strangely off the mark. HOWEVER you quote a 5th gear at 0.83:1 whereas Ashcrofts calculator gives a 5th gear ratio of 0.77 for a 55A variant L77. This looks like where the discrepancy lies. I will have to phone them and see what they say

If the gearing is correct I'll probly try some bigger wheels /tyres in due course if the diffs don't give up in the meantime ( seemed like about 20degrees play when checking it just now but could be everything else in form hub to diff) I want to stick to road biased tyres to keep the noise down as I have removed the back seats and put a ply floor in.

I've recently made the final decision to keep the car and, over time, make it mechanically as good as it should be so I'll look at everything eventually.

I'll let you know what ashcrofts say

if my disco 200tdi needed that sort of money spent on it id be looking at getting another one.... a grand will buy one with a few years life left in it.

300bhp/ton said:

I think your speedo might be out tbh.

The R380 in a 300Tdi has a 0.77:1 5th gear whereas most LT-77's have an 0.83:1 5th.

This translates that the 300Tdi with 28.91" tyres (ie 205/80R16's) will be pulling 64.7mph @ 2500rpm not 70mph.

V8 300 Series Disco's with the R380 did have a taller 5th again at 0.73:1, if your Tdi has a V8 spec R380 then 2500rpm would be pretty close at 68.2mph

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Hi 300

the speedo is roughly 3-4mph optimistic as checked against my garmin, and its definitely an L77 - reverse is on the left. Also Landrover confirm the serial number is as issued when it left the factory. ashcrofts will have an opinion no doubt

ricc said:

if my disco 200tdi needed that sort of money spent on it id be looking at getting another one.... a grand will buy one with a few years life left in it.

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HI ricc

appreciate the thought but some reasons why I can't do the sensible thing.
1 already spent shedloads welding the thing up, waxoyling, hid conversion, teflon swivels, cvs, etc. did the new heater blower motor myself
2 also replaced fuel tank ( previous owner drilled into it while attempting to screw down rotten floor - screw holes - 12- filled with chewing gum )
3 despite being a K reg car it looks ok in rich clients drives cos its shiny on the outside, standard ie not aggressive looking
4 its got professionally tinted windows so my tools are not visible
5 its not a van so doesn't attract LEZ penalties, higher tolls or low life scum ( so much)
6 I like improving things - I did this with my 110 and my lightweight v8 - hated having to sell them.

ashcrofts opinion is that the discrepancy may be caused by us not using the true rolling radius, i.e. we should be measuring from the ground to the axle centre and doubling it. I will do this later and see where it gets to on his calc.

D ashcroft adamant that 200tdi manual disco 1 has a .77 fifth gear.

have measured the rolling radius and put that in the ratio calc.
Mr Ashcroft seems to be right. the flat on the bottom of the tyre caused by the weight of the car is enough to make a big difference to the resulting road speed/revs, which would mean he is right in saying all 4 cylinder 200tdis have a .77 5th gear ratio.
I need bigger tyres then.