Gearbox box has 2 prefixes 41D & 42D

[workingonit]

1999 Discovery II.

I've found references that say the first 3 digits, the prefix, describe a number of things - the ratio of the transfer case, the ratio of the differential, and whether or not the centre lock is present.

Another source says 'Prefix 41D denotes that the unit is not fitted with interlock whilst 42D denotes that interlock is fitted'. The manual TRANSFER BOX - LT230SE DESCRIPTION AND OPERATION 41-13. Other references say 41D and 42D both indicate the centre diff is present.

What exactly do the first 3 digits represent? Are the three numbers meant to be combined to have one meaning or should each character be considered individually? Is it specifically an indicator of transfer ratio, and other things like centre diff lock or differential ratios are by implication or association only?

My gearbox was originally 'dot' punched with a prefix 42D.

At some later stage someone applied an old school analog number '1', hammer punched over the top of the original number '2'.

Was the change in numbering a mistake corrected in the factory or someone making an aftermarket change?

Happy to be corrected, but as I understand it 41D and 42D are both indicative of a 1.211 transfer case ratio. There is even a little sticker nearby saying 1.211. So in theory changing 42D to 41D should make no difference in reporting the ratio specifications to the owner. So why would anyone change the number?

An AI Review even found a reference saying that 42D on the gearbox means a 3.54:1 differential ratio. By chance is there is a differential ratio associated with 41D and not 42D?

[Slunnie]

Thats interesting. I wonder if it has anything to do with this - No 42D. This is from Ashcroft Transmissions

See link, then click the "Technical" tab on the LHS
lt-230-ashcroft-transmissions (https://ashcroft-transmissions.co.uk/product/lt-230/)

TechnicalLT 230 Ratios
Prefix Ratio Application
12D 1.667 2.25 and 2.5 N/A 110’s
13D 1.410 2.5 N/A and 2.5P 90 and 110
14D 1.003 RRC, 3.5, 3 speed auto
15D 1.192 early RRC, 5 speed
20D 1.667 2.25 and 2.5 N/A 110’s
21D 1.667 2.25 and 2.5 N/A 110’s
22D 1.410 2.5 N/A 90, 2.5 TD, 200 and 300 Tdi 90 and 110
25D 1.410 V8 , 5 speed 110
26D 1.003 RRC, 3.5, 3 speed auto
27D 1.192 V8 , 5 speed 90
28D 1.222 RRC V8 and early D1
29D 1.192 V8 , 5 speed 90
32D 1.222 RRC, US spec
34A 1.410 D1, MPI
36D 1.211 late D1
37D 1.211 late D1, US / Japan
38D 1.211 50th anniversary 90
40D 1.211 NAS spec 90, with interlock solenoid
41D 1.211 early D2 with diff lock
43D 1.410 TD5, 90 and 110
47D 1.667 2.25 and 2.5 N/A 110’s
57D 1.410 TD5, 90 and 110
59D 1.211 V8, US spec 90
61D 1.211 D2, non diff lock
62D 1.211 D2, non diff lock
68D 1.211 D2, diff lock
69D 1.211 D2, non diff lock
70D 1.211 D2, non diff lock
80D 1.211 TDCi 90 and 110
81D 1.211 TDCi 90 and 110

[workingonit]

Disco II Diff lock - Ashcroft Transmissions (https://ashcroft-transmissions.co.uk/product/disco-ii-diff-lock/)

Elsewhere on their site the 42D gets a mention.

'If you have the diff lock stud on your unit you will only require the linkage parts, to determine this you will need to find the transfer case serial number and check it starts with either 41D, 42D or 68D'

[Campaspe Man]

1999 Discovery II.

I've found references that say the first 3 digits, the prefix, describe a number of things - the ratio of the transfer case, the ratio of the differential, and whether or not the centre lock is present.

Another source says 'Prefix 41D denotes that the unit is not fitted with interlock whilst 42D denotes that interlock is fitted'. The manual TRANSFER BOX - LT230SE DESCRIPTION AND OPERATION 41-13. Other references say 41D and 42D both indicate the centre diff is present.

What exactly do the first 3 digits represent? Are the three numbers meant to be combined to have one meaning or should each character be considered individually? Is it specifically an indicator of transfer ratio, and other things like centre diff lock or differential ratios are by implication or association only?

My gearbox was originally 'dot' punched with a prefix 42D.

At some later stage someone applied an old school analog number '1', hammer punched over the top of the original number '2'.

Was the change in numbering a mistake corrected in the factory or someone making an aftermarket change?

Happy to be corrected, but as I understand it 41D and 42D are both indicative of a 1.211 transfer case ratio. There is even a little sticker nearby saying 1.211. So in theory changing 42D to 41D should make no difference in reporting the ratio specifications to the owner. So why would anyone change the number?

An AI Review even found a reference saying that 42D on the gearbox means a 3.54:1 differential ratio. By chance is there is a differential ratio associated with 41D and not 42D?

I presume you are intending to purchase the Ashcroft linkage, or do you ask for another reason?
Mine is also a '99. I followed the Ashcroft advice and everything was fine. In another "CDL" thread, Arthur very recently gave advice about examining the top of the box so as to determine the internal set up.

If yours is '99 you may well have the oil leak from the o-ring high up on the engine facing end. When I did the linkage reinstatement, I also removed the transfer case and fixed that leak by replacing the 0-ring. I am definitely no mechanic, but it was achievable (although getting it back in was fun).

Myles

[workingonit]

I presume you are intending to purchase the Ashcroft linkage, or do you ask for another reason?
Mine is also a '99. I followed the Ashcroft advice and everything was fine. In another "CDL" thread, Arthur very recently gave advice about examining the top of the box so as to determine the internal set up.

If yours is '99 you may well have the oil leak from the o-ring high up on the engine facing end. When I did the linkage reinstatement, I also removed the transfer case and fixed that leak by replacing the 0-ring. I am definitely no mechanic, but it was achievable (although getting it back in was fun).

Myles

Thanks Myles for the response.

I'm not intending to fit a linkage at this stage. Very familiar with the o-ring issue - as an experiment I've machined an LT239 case to secure the 'loose side' of the shaft with a bolting system, as it is on the other side - it's in a project vehicle that has not yet been run to test.

My original reason for writing this thread was to ask questions about potential conflicts between a locked diff and the ECU. There seemed to be differing views about 'cut that wire/don't cut that wire', 'lock diff first and then start vehicle/don't', 'get a facelift slabs ECU/don't' etc. But I cut all that out of this thread when checking the prefix revealed a numbering anomaly - and was this going to be a significant issue. It's just life, but I still don't like is when you are trying to familiarise yourself with an aspect of a vehicle you come across unexplained anomalies, both on the vehicle itself and in forum threads relevant to the issue. Was the original 42D centre diff damaged and replaced with a 41D centre diff or the diff was removed altogether? One thread links 42D to the rear diff ratio. Another thread, an official manual, says there is no centre diff if designated as 41D, yet plenty of other threads say both 41D and 42D say diff is present. The only certainty will be to open it up, but no time at the moment.

I have several Discovery 1 vehicles which are a dream to work on by comparison to the Discovery 2. At the moment the vehicle is off the road because I tried to remove the exhaust manifold to resolve exhaust gas leaks only to have the retaining bolts snap in the head - warnings are everywhere on the threads about this issue - the comment 'if the bolts break you'll be in a world of pain' holds true.

The vehicle is either heading for scrap or a bush basher or fire tender on the property if I can't cheaply resolve the broken bolts in head issue - the vehicle initially only cost $1,600 and was otherwise in good condition, except it would not start. It gave the previous owner a lot of grief - dropped the front prop - fuel leaks - the final straw was when the ECU locked itself off from the world and that is when I stepped in. It's interesting to note that all my Discoverys (6) have been purchased from people who have 'had enough' - none were mechanically minded, having failed to conform to the adage 'Land Rover, turning owners into mechanics since 1947'.

I'll give it a few more days to see if someone is familiar with why a change in date stamping may have occurred. My guess is the 42D diff broke, was removed and not replaced, then re-stamped as a 41D to align with an official manual that say there is no diff if it is a 41D OR they replaced the later 42D with an earlier 41D which presumes they really do exist despite what the manual says. And of course what store do you put into a manual when Land Rover itself is a bit ad hoc in what it sometimes does.

[Campaspe Man]

I'm sorry to have made you relive these past (and current) traumas!
I'm presuming that if you could, you would have tried manually operating the locking mechanism on top of the box? I suppose if the vehicle isn't operable you can't know if anything is happening inside... although I'm thinking you could actually turn it over manually in order to get a good enough idea (instead just taking the box out and inspecting it - which might really be the best thing).

Anyway, I can tell you that I did the wire cutting 'trick' (as you've probably read), and the vehicle has worked very well - but I do note the sagely advice that there may be limits to this, and I am simply fortunate to have not yet encountered a problem.


Good luck, Myles

[discorevy]

The 42D was for the U.S. market, which had the Neutral interlock as well as the centre diff lock.

What may have happened is the assembler may have picked up a "42" case and re stamped with a 41 to send off to an Australian market, due to there being a shortage of "41's" that day, it may be unheard of in a German factory, but probably not at Land Rover.... I personally don't think improvisation is always a bad thing, it got them (British and Aussie's) through some tough times.

[workingonit]

I'm sorry to have made you relive these past (and current) traumas!

I'm sorry Miles that you had to read it!![bigsad][thumbsupbig] Hope it won't put you off any other threads I write. The issue will eventually be resolved, but too many other projects on the go at the moment.


The 42D was for the U.S. market, which had the Neutral interlock as well as the centre diff lock. What may have happened is the assembler may have picked up a "42" case and re stamped with a 41 to send off to an Australian market...

Thanks discorevy for that interesting insight. Are you able to shed light on the meaning of 'interlock' or 'neutral interlock'. I've seen sites refer to front and rear 'lockers' at the same time referring to the centre in some way as the 'interlock' but with no clarity beyond that?

[discorevy]

Thanks discorevy for that interesting insight. Are you able to shed light on the meaning of 'interlock' or 'neutral interlock'. I've seen sites refer to front and rear 'lockers' at the same time referring to the centre in some way as the 'interlock' but with no clarity beyond that?

The interlock was required for the North Americans because..... well, you know, there was the possibility (probability?) they could reach for the wrong gearstick and die or something, sort of like the way all modern vehicle systems treat everyone now ( which is making that scenario come true, as the lowest common denominator sinks, but that's a whole other story).

It would lock you out of trying to change T.C. ratios while moving above 5 mph.

As far as trying to research stuff like this by asking AI, you will end up as confused as AI seems to be at this stage, the amount of misinformation it gives is incredible.

Best to do as you have done in this case ( ask Ashcroft, you can Email Dave and he'd get back to you quickly or Aulro )

[workingonit]

It would lock you out of trying to change T.C. ratios while moving above 5 mph.

As far as trying to research stuff like this by asking AI, you will end up as confused as AI seems to be at this stage, the amount of misinformation it gives is incredible.

Best to do as you have done in this case ( ask Ashcroft, you can Email Dave and he'd get back to you quickly or Aulro )

Ahhh, the workshop manual now makes sense '...prefix 41D denotes that the unit is not fitted with interlock while 42D denotes interlock is fitted'.

I'm surprised how quickly I've adapted to AI searches, purely technical it seems OK, and that's all I want really want from it...but yes, be cautious.

Have put the occasional question to Dave and always been pleasantly surprised that, no doubt how busy he is, he is always willing to reply

[Blknight.aus]

If Im understanding correctly, the box would have originally been in the 42D spec they then changed out the parts to make it conform to 41D configuration so manually restamped it to the 41 prefix.

[workingonit]

If Im understanding correctly, the box would have originally been in the 42D spec they then changed out the parts to make it conform to 41D configuration so manually restamped it to the 41 prefix.

Hi Blknight. Yes, that is the gist of it. As Discorevy points out 42D was for the US market with interlock - it may be that the interlock was removed for the Australian market, hence 41D.

I assume the interlock is part of the external linkage and that the locking diff is still in place with no changes to diff components, but I won't confirming that for some long time.

[Blknight.aus]

Hi Blknight. Yes, that is the gist of it. As Discorevy points out 42D was for the US market with interlock - it may be that the interlock was removed for the Australian market, hence 41D.

I assume the interlock is part of the external linkage and that the locking diff is still in place with no changes to diff components, but I won't confirming that for some long time.

the interlock was a solenoid that when activated prvented you from shifting the Tcase, I think but cant confim that it would let you shift into neutral but not out of neutral.

[workingonit]

My wife's Corolla requires a foot on the brake before you can move the shift - now I know what to call the mechanism. Sounds like something we could do without. Annoys me after coming from the Discovery 1.

AI Overview.
The Land Rover Discovery 2 has several interlock mechanisms, most commonly a shift interlock solenoid that prevents the gear selector from moving out of Park unless the brake is pressed and the ignition is on. Other interlocks include a transfer case interlock, which prevents shifting the transfer box lever unless the ignition is on, and a key interlock solenoid that stops the key from being removed unless the gear selector is in Park

[discorevy]

My wife's Corolla requires a foot on the brake before you can move the shift - now I know what to call the mechanism. Sounds like something we could do without. Annoys me after coming from the Discovery 1.

AI Overview.
The Land Rover Discovery 2 has several interlock mechanisms, most commonly a shift interlock solenoid that prevents the gear selector from moving out of Park unless the brake is pressed and the ignition is on. Other interlocks include a transfer case interlock, which prevents shifting the transfer box lever unless the ignition is on, and a key interlock solenoid that stops the key from being removed unless the gear selector is in Park

Thankfully, only the U.S. and Japanese markets.
It's one of the things I like with the D2's when centralising the car on a hoist. Just turn it off and slip it into neutral, no need for ign on etc.
Majority of modern stuff will either furiously beep, apply the E brake, not let you turn ign off, flash dash messages or all the above when you want neutral for hoist work, etc without a work around.

At least, with a semi modern Corolla, you should be able to press the detent to slip into neutral if no Battery power.

[workingonit]

At 5:35 through to 6:36 in the video, Simon laments the amount of electronics in a modern vehicle - 4 sensors in the last metre of the exhaust pipe!

My old vehicles will see me out I think...and may include the D2?

https://www.youtube.com/watch?v=BJO91ca4lD0

[discorevy]

Those sensors which would probably be DPF, NOx, O2 and EGT, would definitely not be in the last metre of exhaust, but the first.

The point holds true though, the technology used has naturally, made modern Diesels less reliable, along with the driver "aids" making drivers feel less need to be engaged with what's going on outside the vehicle, diverting more of their diminishing attention spans to the increasingly large screens on the dash.

Not sure if this means I've entered the realms of the grumpy old man, or because I ride a Motorcycle.

[shack]

Not sure if this means I've entered the realms of the grumpy old man, or because I ride a Motorcycle.

They aren't mutually exclusive Craig!

[discorevy]

They aren't mutually exclusive Craig!

Course, thousands of hours working on Land Rovers wouldn't have any influence on having a serene, positive outlook.

[shack]

Course, thousands of hours working on Land Rovers wouldn't have any influence on having a serene, positive outlook.A serene positive outlook and thousands of hours working on land Rovers ARE mutually exclusive.

I've just overdosed on LR's as you know..

[discorevy]

A serene positive outlook and thousands of hours working on land Rovers ARE mutually exclusive.

I've just overdosed on LR's as you know..

Yes

Quote from NYC government:

"Tolerance is how your body adapts to regular use of a drug over time. As you develop tolerance to a drug, you will usually need to use more of it to feel the effect you want. If you have no or low tolerance to a drug, using even a small amount can increase your risk of overdose."

You may just need to do more, in order to achieve serene levels of stupor, Grasshopper....

Make sure the bar is well stocked first.