Which OD gearbox to install

What is the difference between LH blue and LH black label ? and which one more suitable for a 72B without a switch on the wiper arm ?
Thanks,
Barry

Typically the blue is side fill and set up to operate in 4th only but I believe it can be changed?
Black is period correct for '72, 4 synch, top fill. An OD doesnt really care how it gets power.
RS

If you have the choice, try to fit a blue sidefill one from a late 77 on car. The gear ratios are better than the earlier versions.
The mechanism for the gear inhabitor switch can be modified to make it operate in 3rd. and 4th.

You'll have speedometer issues is you fit a blue label. Are you sure you don't have the switch on the wiper stalk? I thought they all had the switch whether they had overdrive or not.

Sorry, Mike, forgot to mention the speedo that should come with the OD box.
Concerning ratios, it might have been different for the home marked and cars and those shiped to continental Europe. I compared the 1975 blue lable with a 1978 one and they were different on both the boxes in my shop.

Barry. You do have a switch on the wiper arm. It may be so stiff from lack of use that it doesn't feel like it. (boy, I know that feeling).

It's there though. All Federal style MGBs with pillow dash had the OD function built into the wiper switch from 1968-76.

If in doubt. Look at the wiper switch plug. The white and yellow wires are the OD power feed and switched line.

As far as overdrives. I've never had the luxury of having a choice. I just stick in what is around, then deal with the speedo inaccuracy. But then I tend to drive rat cars. The black label gives you OD in 3rd and 4th and is correct for the car.


kelvin

Thanks everyone, Kelvin, my wiper arm moves down for 2 speed wipers and push in for washer, maybe it's broken, i'll check for the yellow/white wires.
Was there any icon on the arm for OD ?
Barry

Given the choice I would go for the black label everytime - it has a better O/D casting than the blue label with the pressed in thrust washer.

Pull the stalk toward you (ON) or push it toward the dash (OFF)
RS

I found the yellow and white wires on the connector @ the bottom of the steering column, so the switch needs replacement.
Barry

Barry. There is no icon on the arm.

The switch plastic latch will be very stiff and could even break when actuated. But give it a try. Most of the original switches I've operated took a lot of force to get over the first click, but then freed up and worked well. No need spending money you don't need to.

k

Kelvin, thanks for your help, i'll give it a try, how about some silicon spray?
Barry

you won't have a problem with the speedo either.........MGBs had 80mm speedos for both 1280 and 1000tpm gearboxes.

Wray, Excellent advice, thanks,
Barry

The wiper/OD switch is definitely quite stiff if it hasn't ever been used. And first you have to figure out if it is stuck in the ON or OFF position (so you know whether to pull or push). But that you can check with an ohmmeter.

It is possible to dismantle the switch BUT it has a little spring (s?) in it and I seem to recall a ball bearing as well. These parts will depart (pun intended) for parts unknown! I would recommend trying to exercise it before dismantling it - but I freely concede you may break it if you force it.

The black label od units are much sturdier. They have a snapring that holds the sprag clutch in place whereas the later blue label ones do not. RAY

We have a black label OD in Kathy;s LE and irt is a 1000TPM because I chaged the speedo gears when I rebuilt it before installation. Thats the biggest difference between the black and blue label OD's....the speedo gearing. If you have a 1280TPM speedometer and a 1000TPM OD...change the gears to 1280 and the speedometer will only be off by 2-3 MPH. Same goes for a 1000TPM speedo and a 1280 OD, change the gears and everything will be fine and dandy.

Thank you, great site.
Barry

Can a black label OD box be used to replace a 3-syncro non-OD box on a 1966 B ? There appears to be a better pool to pick from once you get away from the D 3-syncro boxes.

John