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4.22 diff
Posted: Sun Sep 11, 2016 7:38 pm
by jagnut66
Hi,
I have a 4.22 diff that I have considered fitting to my 948 engined car, as allot of people see this as an improvement that makes the car more long legged when it comes to long distance adventures.
However today when talking Moggies at the East Midlands Branch rally at Denby Potteries, somebody again suggested this as an improvement but said I'd need to change the Speedo to a 90 MPH one, which wouldn't therefore need recalibrating to suite the 4.22 diff. I thought it would only need recalibrating if I changed the gearbox, as the speedo cable is driven from there?? Or am I wrong about this??
Please can somebody advise, many thanks.
I have a couple of gold faced 90MPH speedo's squirrelled away, so it's not a problem if true.
Best wishes,
Mike.
Re: 4.22 diff
Posted: Sun Sep 11, 2016 9:28 pm
by Nickol
you might like to look at the last few Posts in this thread which refer to you question .
http://mmoc.org.uk/viewtopic.php?f=4&t=56976
In any case, the speedo cable is indeed turned by and connected to the gearbox but the diff (as well as the wheel dia) is the deciding facor on which speedo needs to be fitted to give the correct reading.
Re: 4.22 diff
Posted: Sun Sep 11, 2016 10:41 pm
by jagnut66
So basically, having read through the post you gave the link to, if I fit the 4.22 diff, I need to fit a speedo that was calibrated to go on a car that this type of diff was originally fitted to. Which fortunately I have. 
One thing is for sure though --- you will never see 90mph in a Moggy fitted with a 948 engine!! 
Many thanks,
Mike.
Re: 4.22 diff
Posted: Mon Sep 12, 2016 6:44 am
by Declan_Burns
Mike,
When I changed the diff from the 4.22 to the 3.9 on my 1098, I found that the speedo was now perfectly accurate compared to a sat nav. Small corrections (~2MPH) are easily done by re-positioning the needle. Major corrections require either a different speedo, re-calibration or fitting a corrector gearbox. The latter two options being the most expensive.
I would just change the diff, then beg borrow or steal a sat nav and go from there. You might be surprised and not have to do anything.
To re-position the needle I use two small espresso spoons at 180° to prise off the needle. Just make sure to use a layer of felt or a tissue under the spoons so as not to damage the dial face and watch how the needle goes into orbit! I did this recently on the MG TD when I changed the dial to KPH and it works a treat.
Regards
Declan[frame]
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Re: 4.22 diff
Posted: Mon Sep 12, 2016 12:25 pm
by oliver90owner
One thing is for sure though --- you will never see 90mph in a Moggy fitted with a 948 engine!!
Just how many brake horse power can a 948 deliver (just running on pump fuel, not nitro!)? Doubling the output should be more than enough if fitted with the right gearing?
Re: 4.22 diff
Posted: Mon Sep 12, 2016 5:56 pm
by jagnut66
When I changed the diff from the 4.22 to the 3.9 on my 1098, I found that the speedo was now perfectly accurate compared to a sat nav. Small corrections (~2MPH) are easily done by re-positioning the needle. Major corrections require either a different speedo, re-calibration or fitting a corrector gearbox. The latter two options being the most expensive.
I would just change the diff, then beg borrow or steal a sat nav and go from there. You might be surprised and not have to do anything.
To re-position the needle I use two small espresso spoons at 180° to prise off the needle. Just make sure to use a layer of felt or a tissue under the spoons so as not to damage the dial face and watch how the needle goes into orbit! I did this recently on the MG TD when I changed the dial to KPH and it works a treat.
Very interesting -- thanks.
Re: 4.22 diff
Posted: Mon Sep 12, 2016 9:00 pm
by Nickol
Declan_Burns wrote:Mike,
When I changed the diff from the 4.22 to the 3.9 on my 1098, I found that the speedo ......
I did this recently on the MG TD when I
changed the dial to KPH and it works a treat.
Regards
Declan[frame]
[/frame]
DEclan, where did you manage to source a Km/hr dial from ??????
Re: 4.22 diff
Posted: Tue Sep 13, 2016 6:15 am
by Declan_Burns
Nickol,
I know a chap in Holland who makes them (both the dished and flat versions) and sells them at shows. He also makes rev counter dials and replacement clocks for the T-Series. The quality of his work is excellent.
Regards
Declan
Re: 4.22 diff
Posted: Tue Sep 13, 2016 9:36 am
by Nickol
Declan_Burns wrote:Nickol,
I know a chap in Holland who makes them (both the dished and flat versions) and sells them at shows. He also makes rev counter dials and replacement clocks for the T-Series. The quality of his work is excellent.
Regards
Declan
Can I get to know this chap as well???? Would much prefer to have Km as the dominant reading on the dial
Re: 4.22 diff
Posted: Tue Sep 13, 2016 11:23 am
by Declan_Burns
Nickol,
He doesn't make any Morris Minor parts but he will probably have a stand at the MG Parts jumble in Houten in Holland just after Christmas.
Regards
Declan