Thread: Gearbox box has 2 prefixes 41D & 42D

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

Technical

LT 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

Disco II Diff lock - Ashcroft Transmissions

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'

Originally Posted by 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?

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

Originally Posted by Campaspe Man

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.