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MG MGB Technical - SPEEDOMETER 5227/06

Hey,
I am having a hard time sorting the problem on speedo.
I installed a 1976 OD in my 1972. Changed speedo to a 5227/06 which supposedly came from a 1973 OD, but it reads steady at 20+% low. 40=52, 60=72 etc.

Couldn't find the 5227/06 in the cross references. Any help greatly appreciated.
James Huggins

Look at the small numbers at the bottom of your speedometer, it probably reads 1280 turns/mile. You need a 1000 turn per mile speedometer to match the 76 transmission. It doesn't have be for an overdrive transmission. The correct speedometer was used in 75 and 76 model cars. Or you can have a speedometer repair shop convert and recalibrate your speedometer or they can build a ratio adapter to fit in the drive cable.

Clifton
Clifton Gordon

There are several 5227 speedos used in the MGB, but 06 isn't one of them according to my list. They are all 1280tpm as Clifton notes i.e. for chrome bumper gearboxes and you need a 1000 for a rubber bumper gearbox. The odd thing is that even though chrome bumper cars had the same tpms for OD and non-OD they used different speedos. There was no difference in speedos between OD and non-OD for rubber bumper cars.
Paul Hunt

Hey Guys,
Thanks for the reply. I figured out I need 1000TPM but can't find one that will fit the car ie 3+"

Paul: a question, can I use the pinion out of the 72 not OK for the pinion in the 76OD? Also, thanks for bein here, you are always a help.

The non 72 non OK has 26 teeth, have'nt gotten uder the car to check the 76 OD for teeth number.
James Huggins

I hope u understood the last post, forgive the spelling, I didn't check it before I hit send, fat fingers. 76 tranny=OD, 72 original tranny=non OD
James Huggins

I hope u understood the last post, forgive the spelling, I didn't check it before I hit send, fat fingers. 76 tranny=OD, 72 original tranny=non OD
James Huggins

Hey All,
Did a little research and my 72 calls for a 5231/00-Non OD, and a 5231/04 for the OD. I'm going to see if I can find a 5231/04 or send mine out to Nossinger.
James Huggins

The overdrive speedometer will still be a 1280 tpm unit. I don't know why the OD and non OD speedometers have different part numbers, I have interchanged them with no obvious problems. Changing the pinion gears will not work unless you change the internal drive gear to match the pinion you want to use. Changing the internal drive gear requires some transmission disassembly.

Clifton
Clifton Gordon

As Clifton implies, both the pinion and the gear are different between OD and non-OD, having a different number of teeth in the former case and a different number of starts in the latter, even though they give the same overall result. Because one gear is on a non-OD output shaft and the other is on the OD output shaft I don't know if they are even interchangeable.
Paul Hunt

James,
Clifton gave you some good advice about what speedo to use - get one from a 75 or 76 MGB.

Here's a link to an article I wrote about this, hopefully you'll find it usefull.

http://custompistols.com/cars/articles/ts_od_gearbox.htm

Tom
Tom Sotomayor

Thanks again everyone.

Tom, isn't the 75/76 speedo larger in diameter. I checked a 76 previously, and it looked larger, didn't actually measure it.
James Huggins

James

Not up on USA dashboards but are they the same diameter clocks 4inch as ours?

If so theonly speedo that will be near are the Early Pull Handle car speedos which are 1040 and 1060 tpm so will be near enough.

Steve
Ste Brown

James,
No. For USA cars the speedos were 4" from 62-67 (1020 or 1040 tpm). From 68-76 they got smaller (1280 tpm from 68-74 & 1000 tpm from 74.5-76). For 77-80 they went back to 4" (1000 tpm).
Tom Sotomayor

This thread was discussed between 19/08/2008 and 21/08/2008

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