1.667:1 transfer box in a disco?

jamesmartin said:

no, and never had egt issues or any other apart from a sprung tow hitch frame he has fitted at the dealers as the 6 wheel trailer held the rear of the truck up or lifted it on uneven roads ,the truck would let air out of the suspension and it would lower the rear too much and compressor to level it up was too slow,

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Air suspension, oh sh!t.!
So pleased mine is on springs! Did the guy have a Dixon-Bate or what?

jamesmartin said:

youd expect a lot of warped manifold issues at least,which occur with standard discos especially after the loads he pulled the regularity and years concerned,never had head problems or gasket changed unlike mine which is bog standard

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Yep, I got the warped exhaust manifold, but then many seem to get it, towing or not, so not absolutely sure it was down to towing. but it can't have helped!

I've never had warped manifold, not even after those high EGTs and i used to tow a big boat quite often...in exchange i had a cracked head

sierrafery said:

I've never had warped manifold, not even after those high EGTs and i used to tow a big boat quite often...in exchange i had a cracked head

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Don't know whether to say "lucky you" or not. Cracked head v warped manifold, not an easy one to call which is the better sh!t to have! Both are a pain in the ar se! and the second is often worse if the studs fu ck off and cause damage in the process.

Stanleysteamer said:

Must have misunderstood, did you fit the overdrive on a Disco? If so, you have cheered me up as I always though it ought ot have been possible with a bit of bodywork modification.

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yes m i did have to cut a piece out and weld a bit back,under the cubby box rear

Stanleysteamer said:

Air suspension, oh sh!t.!
So pleased mine is on springs! Did the guy have a Dixon-Bate or what?

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yes secured to a sprung frame, the air kept the car level with the weight but couldnt cope when trailer lifted the car

Stanleysteamer said:

Yep, I got the warped exhaust manifold, but then many seem to get it, towing or not, so not absolutely sure it was down to towing. but it can't have helped!

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the harder the engine is working the greater the heat,so towing would contribute certainly,obviously some manifolds have a greater threshold than others

Stanleysteamer said:

Cracked head v warped manifold, not an easy one to call which is the better

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at over 1300 quid as costed me the new AMC head(labour included) maybe the manifold is better

jamesmartin said:

yes m i did have to cut a piece out and weld a bit back,under the cubby box rear

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Nice one!

Russell 1 said:

Has anyone put a 1.667:1 or a 1.4:1 transfer box in a discovery? If so what does it drive like? I do a fair bit of towing and I find pulling away difficult with any sort of weight in the trailer. As it will need a new gearbox soon I'm thinking I could be wise to change the t box.
Motorways and driving over 50 are not needed where I live.

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I did transfer box rebuild from Ashcroft, and due to some circumstances I opted for 1.41 ratio on high gears.
It drives smoother, accelerating easier and feels like driving’s with factory tires, except torque converter lockup.

Russell 1 said:

How does it cope when it's in low then? Only does about 20mph in faith gear.

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This is not affecting low gearing at all.

sierrafery said:

Bigger tyres would cause much more harm than a remap for a Td5.... a good remap has no ill effects for the engine no matter of mileage, on the contrary, while bigger tyres = higher EGT which kills the engine slowly...that's a fact... to not speak about how gutless it will be with bigger tyres and no remap

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Regarding the ill effects of remap: why would you say there are no bad effects on the car regardless of mileage, when Pete Bell say it is not advised to do it when engine has big mileage?

now, I would like to explain something and ask you opinion then:
I have the Discovery 2, with automatic gearbox. Fitted 33 tires, which caused the engine to work harder. Fitted an roof rack, bull bar and winch. So that means that the engine was forced to work hard.
Now, you have to compensate the added load, which means you can do that by changing the diff ratio. Otherwise, you can change the transfer box ratio, which will have almost the same effect except you do not remove the stress from propshaft and you do not touch the low range gearing.

after fitting 1.41 transfer box, I observe the engine acceleration is nearly as before fitting bigger tires. It drives easy on highway in 4th, when earlier I was driving only in 3rd with factory transfer box and 33 tires...

only one unsolved issue now, the Torque Converter lockup is not working. But I am not sure why, because when I fitted the transfer box, I also removed the transmission, replaced the flex plate with a HD one, changed the oil, some seals etc...
I can also expect that I touched something in the transmission sump as well...

so, in conclusion, I disagree that these mods are against the engine lifetime, but, I consider that these mods may not be the only one required.

I will talk to Pete Bell regarding mapping and ask again his opinion.

sandu said:

Now, you have to compensate the added load, which means you can do that by changing the diff ratio. Otherwise, you can change the transfer box ratio, which will have almost the same effect except you do not remove the stress from propshaft and you do not touch the low range gearing.

after fitting 1.41 transfer box, I observe the engine acceleration is nearly as before fitting bigger tires. It drives easy on highway in 4th, when earlier I was driving only in 3rd with factory transfer box and 33 tires...

only one unsolved issue now, the Torque Converter lockup is not working. But I am not sure why,

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Please read again posts 17 nd 18 cos i explained there as short as i could... the main factor is the VSS which with those huge tyres is seriously altered, the EAT ECU is managing the lock-up and shift control based on CAN messages from the ECM and vice-versa the ECM addapts fuelling to the EAT inputs... i'm not surprised at all that your autobox is not behaving well

the elements in the following table were "calibrated" from factory for standard dimension tyres and they have to match for a proper management. As you altered the ratio and the tyre sizes the torque request and road speed will be different at a certain throttle position and rpm and the ECM will adjust fuelling as to achieve a proper algorythm .

Now see the involvment of VSS


depending on the remapper they usually work with the injection duration maps or with AFR as to increase power but the other tables are the same so the whole ''matrix'' is mixed up, a remap for such mods can be done dynamically while watching the EGT and adjusting things as to keep the power and reduce the EGT but a ''generic'' power remap can give you a good throttle response but the EGT can be up in the sky

As i said i made many live tests with EGT and ECT gauges fitted with different tyres and remapped chips and i was amazed at the beginning then i started to study hard and i'm not amazed anymore. I also have a friend with automatic Eu3 engine and modified ratio + huge tyres and after he fitted EGT and ECT gauges on my advice he backed up... maybe you'll do that too if you see EGT 850+*C and ECT around 105*C under prolonged load

Everybody can have his own oppinion and i respect it but i had many debates on this and for those who made such ratio and huge tyre mods i insisted with the obsessive question: WHAT EGT DO YOU GET UNDER HEAVY LOAD ? and i didnt get any answer.

So i hope you agree that high EGT is killing the engine slowly that's why i told you to fit a gauge ASAP(ECT gauge would be good as well) and if after that you'll see the EGT within decent limits with your mods then you can contradict my theory with a strong argument

I rest my case.

... and I still say that if your machine is struggling to pull 2.7 tonnes then there is something wrong with it.
No point in remapping it or changing ratios until you are absolutely sure it is running as a standard Landy ot the same age should.And I seriously do not think you will find that. It should tow 2.7 tonnes all day long, unless you are expecting it to fly up hills like a gazelle.

It will pull the weight ok the problem is pulling away without murdering the clutch, 0 to 10 mph because first is so bloody tall. From 10mph and up it is plenty good enough. I have tried using low but is difficult shifting from low to high at speed.

Stanleysteamer said:

No point in remapping it or changing ratios until you are absolutely sure it is running as a standard Landy ot the same age should.

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A standard td5 auto would behave well with standard dimension tyres too but with such huge tyres it's normal to be sluggish IMO

In earlier posts you said you were on standard tyres, you also said

Russell 1 said:

2.7 tonne is the max I pull at the moment but it really takes a lot of clutch slipping to pull away in 1st high so I have been using 1st low and then 1high. Even once I've pulled away the gears seam far to high. Empty with no trailer it is fine but I feel it's working to hard with a trailer and won't last.

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Russell 1 said:

as it is, its not really up to the job of heavy, regular towing.

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But in your last post you state "from 10 mph up it is plenty enough" which rather contradicts "once I've pulled away the gears seam far to high" and that "it isn't really up to the job of ... towing."
So we have a dilemma. Either it IS up to the job of towing or it isn't.
The weight you say it is towing is well within its capacity.
So I would suggest you ensure have a diagnostic done, ensure the air filter is clean,etc, i.e. that the engine and its fuelling is up to spec. For instance a dirty or dodgy MAP can give exactly what you describe.

sierrafery said:

A standard td5 auto would behave well with standard dimension tyres too but with such huge tyres it's normal to be sluggish IMO

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Agreed but he said in about post #10 that it is on standard tyres, at the moment. If anything he could do with smaller tyres!

yesterday evening whilst driving home on a flat road, the torque converter locked up at 80km/h... I drove it this way approx. 5km until I had to touch the brake pedal...
by this point, I am very confused why the torque converter is locking up some times and is not locking up other times...

sandu said:

by this point, I am very confused why the torque converter is locking up some times and is not locking up other times...

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So are the two ECUs, confused by erratic inputs... even a 3 degree climb or descent on the road(which you'll not notice while driving), a +/- 5 km/h head or tail wind or 1 mm travel on the TPS can make a difference cos the torque request variation is much different than with standard tyres... with your 275/70/18 tyres your real speed was around 102km/h with the speedometer on 90 as on the pic you posted also a ''normal" D2 auto would have had around 2200 rpm at that speed on flat road without accelerating not 2400 like your's ... the whole management on your vehicle is mixed up by those huge tyres believe me or not

sierrafery said:

So are the two ECUs, confused by erratic inputs... even a 3 degree climb or descent on the road(which you'll not notice while driving), a +/- 5 km/h head or tail wind or 1 mm travel on the TPS can make a difference cos the torque request variation is much different than with standard tyres... with your 275/70/18 tyres your real speed was around 102km/h with the speedometer on 90 as on the pic you posted also a ''normal" D2 auto would have had around 2200 rpm at that speed on flat road without accelerating not 2400 like your's ... the whole management on your vehicle is mixed up by those huge tyres believe me or not

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First off, I beleive OP @Russell 1 is still on standard tyres although admittedly according to the manual, two sizes of tyres are "standard".
The reason I think this is cos this is what he has said.

Russell 1 said:

I will probably fit bigger tyres at some point.

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i.e. hasn't done it yet

Russell 1 said:

Current tyres are standard

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Russell 1 said:

Everything is standard

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Although he has mentioned and asked questions about fitting bigger tyres, I don't think he has done so yet.
On the lock up thing. Mine locks up, as it should, at about 55 mph which is 88kph. but it CAN sometimes lock up lower, but I agree entirely that it takes fu ck all to drop out of lock up at about that speed. I know this cos I try to use it as much as poss but in France where until v recently the speed limit was 90 kph it wasn't easy at all to get it to lock up and then stay there, even using cruise control. Mine is on stadard tyres. Once IN lock up the revs vary a bit but they do drop, Mines an auto by the way.
As far as I can tell from his (Sandu's) pic, the speed is about 56 mph and the revs are a shade over 2200 rpm. But considering he has the 33" tyres and has also changed the ratio in the box, I think he is doing very well to get it to behave sensibly at all!

Occams Razor; you changed the transfer box ratio, you changed the tyres to bigger ones, there is your answer. Sometimes we just dont want to admit defeat!