What Does "LH" Mean in Transmission Talk

I see people refer to a LH gearbox a lot. What does it mean?

LH is overdrive parlance.

Laycock de Normanville, the manufacturer of overdrive units on English cars, made a bunch of types over the years. A-Type, D-Type, J-Type, LH-Type, P-Type.

MGB's had D-Type overdrives fitted from 62-67, and LH-Type from 68-80.

Note, there were also two different types of LH-Type overdrive, the black and blue label. One is earlier, one is later (I forget which one) but they are "essentially" the same.

OK, that explains it. I thought LH meant that it was for a Left Hand drive car but that makes about as much sense as a metric Crescent Wrench.

The Black label LH overdrive was used from '68 to '74. The Blue label LH overdrive was used from'75 until '80. RAY

I knew Ray would know! :)-D

Interesting - the O/D I have is a black label, yet when I bought it, the yard had it tagged and recorded as a 76. It probably is a 68-74 unit as you state, Ray, but either the yard screwed up or something with the title when they parted the car out. Doesn't matter to me because when I got it the recorded mileage (which, from examination, probably was correct) was only 20K miles. That was more important than "age" at the time. Learn something every day tho.

OK my turn. The labels are located where?

These really are great overdrive units. I installed mine over 25 years ago and the only thing that I've done to it is replace the oil and filter twice. Oh, and the solenoid failed after only 38 years! Bob, a little knowledge is a dangerous thing. I should know, because it's all that I have left. RAY

in a British car it could also mean Leaking Heavily(:P)

Okay, my turn to divert the thread a bit.......

I have a running '73 with no OD and a '76 parts car that does have an OD ( don't know which one). What's the best way to upgrade my '73; swap entire tranny's, or is it reasonable to just pull the OD out from under the parts car and install on mine?

David

David,

Sorry to say the overdrive is not just a separate unit that can simply be swapped onto another gearbox. While it appears separate, it requires a unique mainshaft in the gearbox, and complete disassembly of the gearbox is necessary to swap out the mainshafts. So, clearly, your best and only option is to pull the engine and gearbox, swap in the overdrive gearbox, and take care of all the might-as-wells while it's apart...

Dick

Thanks Dick.

That was my first assumption, but something was said that made mr think (hope) there might be an easier way out. Oh well, I've pulled engines before!