Page 1 of 2
#1 V12 Auto to Manual Conversion
Posted: Sat Aug 06, 2022 2:21 pm
by George
Hi Everyone, I am aware this is an old topic and I have read most of the excellent information about converting on this site but it is mostly now dated and so I was hoping to pick up the latest advice from anyone.
Most of the conversion kit suppliers mentioned here no longer supply these kits, the one supplier that I got any sensible information from was Wilkinson's and their price for the Tremec T5 kit and all the other parts needed for the conversion is £10k.
The Driven Man (American Powertrain) is a comparable price when adding in all the other parts needed.
I have also been looking for a used 4 speed Moss KFN box with Laycock de Normanville o/d but when I asked a gearbox specialist how much it would be to refurbish it he said that the parts for these are now obsolete therefore my question is are these parts really obsolete and unavailable because if that is the case then it would only leave the route of a new gearbox.
If anyone here has any helpful advice on either sourcing a new Tremec T5 kit or the 4 speed + o/d I would very much appreciate it.
Many thanks in advance
George
#2 Re: V12 Auto to Manual Conversion
Posted: Sat Aug 06, 2022 3:31 pm
by mgcjag
Hi George.....the Moss gearbox and over overdrive is the wrong unit and dosnt fit an E type...xj6 box and compact A type overdrive is the option (as mentioned many times on the forum).or other jag medels with the compact A o/d.....very different to the moss and long overdrive....Steve
#3 Re: V12 Auto to Manual Conversion
Posted: Sat Aug 06, 2022 4:04 pm
by George
Hi Steve,
Yes your are right the word Moss crept in there, the one I have been looking for is the KFN with Laycock de Normanville o/d as I mentioned in my original post but thank you anyway.
George
#4 Re: V12 Auto to Manual Conversion
Posted: Sat Aug 06, 2022 11:30 pm
by lowact
ODs still available.
ODSpares in Rugby, Warwickshire:
http://www.odspares.com/
Overdrive Repair Services in Halfway, Sheffield.
https://www.overdrive-repairs.co.uk/
Also SNGB on-sell most parts.
Auto to manual is a big job, why not a 4 speed auto with 2.88 diff?
#5 Re: V12 Auto to Manual Conversion
Posted: Sat Aug 06, 2022 11:43 pm
by abowie
#6 Re: V12 Auto to Manual Conversion
Posted: Sun Aug 07, 2022 9:31 am
by George
Hi Lowact- od spares is one that I was not aware of so thanks for letting me know, Overdrive repair Services yes I did know about this one.
Also thanks for this 4 speed auto suggestion but if I change it will be to manual.
Cheers
George
#7 Re: V12 Auto to Manual Conversion
Posted: Wed Aug 10, 2022 12:41 pm
by George
When using an XJ6 4 speed KFN gearbox with compact Laycock de Normanville o/d am I right in thinking that the current auto bellhousing cannot be used and a manual bellhousing needs to be sourced and if so what is the part number for this - I believe it is C14444 but would like confirmation before sourcing or an alternative please.
Many thanks
George
#8 Re: V12 Auto to Manual Conversion
Posted: Wed Aug 10, 2022 8:19 pm
by MarekH
Dear George,
purchase a copy of the 1974 etype parts manual and compare the diagrams of the auto car versus the manual car. Not only does that tell you all of the parts required, but it also gives you their part numbers and how they fit against each other.
Your new gearbox needs to have the two bosses on the right hand side of the gearbox case as this is how the clutch slave cylinder is mounted. A six cylinder car gearbox casing may not have these, as they have the slave mounted to the on the bellhousing, rather than on the gearbox.
kind regards
Marek
#9 Re: V12 Auto to Manual Conversion
Posted: Wed Aug 10, 2022 8:35 pm
by George
Hi Marek
Thank you for your reply.
The reason I have specified a KFN gearbox is because that is the one with the 2 bosses on the RHS for the slave cylinder but thanks anyway.
George
#10 Re: V12 Auto to Manual Conversion
Posted: Wed Aug 10, 2022 9:20 pm
by MarekH
KFN and KPN also have a different (lower) first gear ratio compared to the standard boxes. This makes it an attractive option if you have swapped out your differential, but might leave with a headache of a first gear if you haven't.
kind regards
Marek
#11 Re: V12 Auto to Manual Conversion
Posted: Wed Aug 10, 2022 9:36 pm
by George
I chose the KFN gearbox based on the past very knowledgeable posts of Bill who has written some very good 1st hand posts on this subject but whilst there are plenty of posts saying that a different bellhousing needs to be fitted none that I can find give the part number for it.
My car is a California import and I believe the diff is a 3.5.
Cheers
George
#12 Re: V12 Auto to Manual Conversion
Posted: Thu Aug 11, 2022 1:39 pm
by Bob.
HI George,
For a US spec S3, auto diff was 3.31, manual was 3.54.
Bob
#13 Re: V12 Auto to Manual Conversion
Posted: Thu Aug 11, 2022 2:02 pm
by George
Thank you Bob, much appreciated.
Cheers
George
#14 Re: V12 Auto to Manual Conversion
Posted: Thu Aug 11, 2022 2:27 pm
by mgcjag
Hi George...have a read through this thread.....it mentiones "special " bellhouseings for Getrag conversion....but when useing xj6 4 syncro box then a standard V12 setup....bellhouseing, clutch etc.....C33660 is the part number showing for a V12 manual bellhouseing but dont take my word for it...just check......Steve.....ps..your too quick
viewtopic.php?f=6&t=11842&p=96007#p96007
#15 Re: V12 Auto to Manual Conversion
Posted: Thu Aug 11, 2022 2:32 pm
by George
Hi Steve,
You didn't include the link to the thread.
Cheers
George
#16 Re: V12 Auto to Manual Conversion
Posted: Thu Aug 11, 2022 2:34 pm
by mgcjag
Link added

look at post 4
#17 Re: V12 Auto to Manual Conversion
Posted: Thu Aug 11, 2022 2:56 pm
by George
FTAO Steve and anyone referencing this thread in the future, I sent Bill who is a very knowledgeable and much respected contributor on this subject an email and he kindly informed me that the bellhousing part number is C33660 which confirms the same as in Steve's link so many thanks to the both of you.
Cheers
George
#18 Re: V12 Auto to Manual Conversion
Posted: Fri Aug 12, 2022 7:58 pm
by BobV12
For my V12 OTS rebuild I’ve gone for an XJ6 box, which has the same ratios as my original box, plus a Laycock A compact overdrive and I got O/D Spares in Rugby to refurb both and bolt them together which they have done. The car is not finished and so I have yet to test it but I was pleased with the service I got there and the finish.
Retains the authentic gear change but gives a fifth gear and I always enjoyed using overdrive on an MGB years ago.
Hope this of use
Bob
#19 Re: V12 Auto to Manual Conversion
Posted: Fri Aug 12, 2022 8:32 pm
by George
Hi Bob
Yes that is useful information how much did OD Spares charge you for the work and which bellhousing did you use?
George
#20 Re: V12 Auto to Manual Conversion
Posted: Tue Aug 16, 2022 6:10 am
by BobV12
Hi George, around £1,100 and I will use the original bellhousing, keeping the original unrestored gearbox in store.
Bob