MG MGB and MGB GT Tech Talk
I guess I should have posted this BEFORE I bought it but ... what should I look for in a used 1974 overdrive gearbox that is off the car? It was a craigslist impulse buy. Seller said it worked fine and I figured it was worth the gamble for $500.
Rick, don't worry, it's a late box...there's a very good chance it's good and can go right into the car.
I know nothing about overdrive units themselves, but pull the side cover on the gearbox and see for shavings or chunks missing in any of the gears.
Clean her up real good, replace front seal and rear seal on OD unit...bolt 'er up!
Remember that many late model gearboxes get thrown away because they are so strong and people rarely need replacements! This is not the case for OD units obviously but the front half is all the same. They're that bulletproof! :)
Rick, I just put one in last year. I checked that the solinoid "clicked" when 12V applied (I used an external battery and fused jumper wire).
I also checked the safety lockout with a test light. If this circuit is faulty and the OD engages in reverse, damage to the one-way clutch in the OD occurs. Check John Twist's you tube videos on all this... very helpful.
well, i paid 700 for a similar LH od - based on seller's similar assurances
it turned out that the OD works fine indeed - BUT to have a really bad 3rd gear synch problem
before you go to all the trouble to install - open it up and check the synchro clearances - esp the 3rd which is apparently the primary one that everybody reports having clash and popping-out problems with
there are many posts here about the synchro clearances issues
and look at all the gears for wear & chipping on the tooth edges
good luck
pull off the overdrive filter cover on the bottom. look for chunks of metal. a small amount of "paste" on the magnets are ok but wipe them off. with the overdrive filter removed look up inside there while you are turning the output shaft and check that the pump moves in and out. this is in addition to everyone else's suggestions.