MM and series II Speedos

[leyther8008]

Can anybody tell me the TPM (turns per mile) number for one of the above please? usually to be found on the face somewhere.
Thanks

[DAVIDMCCULLOUGH]

This link may help, I had a new old stock one for sale and didnt know if it was MM or S11 but Mike Perry knew the answer!!

http://www.mmoc.org.uk/index.php?name=P ... ic&t=23219

[mike.perry]

Series MM is 1600, speedo code is X70620/2. Series II is 1000, code X70620/7.
X69982 and X69982/5 are also 1600 and have trip meters

[markattard]

Also please mike could you pls advice on what are the repercussions on using a series 2 speedo with an 1100 gearbox, and what is the th TPM of the 1000 speedo?

Actually it should not make any difference in the reading as the size of the wheels is the same, but its good to hear it from the experts.

[bmcecosse]

There's a thread on Speedos - with TPMs etc - I'll let you search for it!

[mike.perry]

In theory there should be no difference which gearbox is used as the speedo drive is taken from the output shaft of the gearbox. The early and late Series II used the same box and different speedos with no problems.
There are a multitude of 1000 speedos all with different serial nos and several TPIs. The table is posted on the message board somewhere. I will let you decide which speedo is most suited to your needs. Remember that speedos tend to over read on standard setup so may still be accurate with a higher diff. For instance a 1408 speedo for a standard 4.22 diff 1098 is, on my traveller, within 1mph using a 3.9 diff and 175x80 x13 tyres which are slightly larger than 155x14 tyres. The best solution is to check the speedo against a sat nav.

[liammonty]

Unfortunately, I think it will make a difference- it certainly does when changing from an 803 'box to a 948 'box. As mike says, the drive is taken from the output shaft- however, the gear on the output shaft of the different boxes is different, as is the speedo drive which screws into the 'box and mates to it. As a result, my early SII with 948 running gear now has a speedo that over reads by about 40%, and I've got to strip the box in order to change the speedo drive gear on the 3rd motion shaft in order to cure it (When that's changed, the original 803 speedo drive will fit the 'box). I reckon the problem will be the same with the 1098 box.

I hope this makes some sense, and good luck!

[mike.perry]

Maybe there is a change of speedo drive gear between the gearbox fitted to the early SII with the small speedo and the gearbox fiitted to the late SII with the central speedo
The workshop manual only lists one speedo drive gear, 5/13 ratio on a 948 gearbox.
When I had an ex GPO van I changed engines and gearboxes from the original 803 to 948 and then 1098 without any speedo problems. I decided that it was a little on the low geared side with the 1098 engine and box and swapped the diff from a 5.375 to a 4.55. At the same time I changed the speedo to a 4.55 1098 van speedo.
Changing from a 1098 engine and box to a 1275 engine and eventually 1275 box in the Traveller didn't give me any obvious speedo problems. When I fitted a 3.9 diff I checked the speedo against a sat nav and was surprised to find that it was accurate to within 1 mph so obviously over read on the 4.22 diff.
If anyone can come up with a list of which speedo drive gears fit which gearboxes I will add the information to my speedo chart.

[IslipMinor]

The Series II central speedo is 1,000 TPM because the skew gear ratio on the gearbox output shaft is different to the 948/1098 remote control versions. The SII ratio is ~4:1 and the 948/1098 is ~2.6:1. I don't know about the earlier 'small' speedo version.

With a Toyota 5-spd, 3.9 diff and 185/70x13 tyres I needed ~1000 TPM, so have used the centre part of the SII speedo, a kph dial going up to 120 and reclibrated just the speedo part to suit the dial. The odometer is perfect!

[mike.perry]

"Original Morris Minor" p.53 lists a change of speedo drive gear to 3/4x26TPI in Dec.'53. Ths co-insides with the change from Morris to A Series rear axle. It is however, a year before the car was restyled and the speedo changed.