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MG Gearboxes for Dummies

I had never even seen the inside of a gearbox until I started working on the gearbox in my TF-1500 earlier this year. So I am definitely a DUMMY! This month’s Tech Tip is not a fact filled how-to. Instead it’s a recap of my gearbox journey and an encouragement for other newbees like me to tackle a task on your MG that is outside your comfort level. You can do it.

My journey started in January when I decided to replace the rear case of my gearbox that had a broken mounting eye. I bought a rear case from Will Bowden. Club members helped me remove the gearbox. With information in my workshop manual, a wonderful gearbox video by Barrie Jones, and advice from club members and the internet, I dove in.

I rinsed out the gray slurry that covered everything inside the gearbox. I chased the threads in the case with a shop-made thread chaser. I installed a new clutch disk and pressure plate from Moss. The rear case with new bearing and seals went on with no problem. A coat of Bill Hirsch MG Red engine paint made it look brand new. Once again, club members came to my rescue and helped me install the gearbox. I had cut new floorboards and bought new carpet. So I installed them plus the rest of the interior, lowered the car from the jack stands, and set off for the All Brit Car Show and for GOF. First time that I had driven the car in three months.

WTF!!! I started the car, put it in gear, and slowly let out the clutch pedal. The whole car shook like a paint mixer. Damn the torpedoes, I’m driving to GOF.

Glenn Lenhard kindly offered to drive my car at GOF and diagnose my juddering problem. He told me that my new pressure plate could be bad, not uncommon. But then he said that he was more concerned about the gear noise. I was crushed. With AAA card in hand, I limped back home. It needed a full tear down and rebuild. For the third time, club members came to help me move the gearbox.

I quickly learned that I didn’t have the expertise to be able to distinguish bad parts from usable parts, and I didn’t know what the acceptable clearances should be. Club members and MG owners around the world provided the information that I needed. “Professor” Will Bowden gave me a hands-on gearbox cram course at his shop. Jack and Brian Collins made a few emergency trips to my house to point me in the right direction.

I found that the hardened surface of the layshaft was breaking up and was probably the cause of my noisy gearbox. First gear on the laygear was badly pitted, first gear hub and gear were damaged, and shifter forks were worn thin. Perhaps the gray slurry of iron and steel dust that I had rinsed out of the box served as a cushion to the worn parts. Will B. supplied most of the replacement gears, forks, and even a main case. A new laygear came from Hugh Pite in Canada. Other gears and parts from the usual suppliers.

So, now it’s July and I’m finally starting to wap up the assembly. I painted the case again, polished the brass parts, and lockwired the shift selectors and speedo drive into place.

But I still didn’t know if the rebuilt box would judder and bounce me out of the cockpit like it did the last

time. Then I received a call from Will. He and Mike McCormick were installing the clutch and pressure plate onto Mike’s TD that he is restoring at Will’s shop. When they inserted the clutch alignment tool to position the clutch, they noticed that the tool was not sitting in the center of the pressure plate. Something was wrong.

A slight retracing of events …

I had phoned Moss Motors to discuss my juddering clutch after Glenn Lenhard had told me that the problem might be a bad, although new, pressure plate. Moss suggested that I purchase a second pressure plate and then return the first one if there was no problem with the second one.

Back to the story …

Will asked me to come to his shop and to bring the first pressure plate and the second pressure plate that I had purchased from Moss. I also brought the original pressure plate that was on the car when I bought it. We did some basic measurements and then mounted each pressure plate onto Mike’s TD. It was easy to see that my first pressure plate from Moss was adjusted incorrectly and the second one was OK. Mike’s pressure plate was also adjusted incorrectly and is being returned to Moss.

I installed the replacement pressure plate and phoned Brian Collins at 9:00PM to beg him to help me install the gearbox. A little grease on the temporary studs and on the locator pins and it popped right into place.

I spent the next day installing the interior and adjusting the clutch etc. Lowered the car. Started the engine. Put it into gear and slowly let out the clutch. OMG. The car moved forward. No judder. No noise!!! It may fall apart tomorrow, but right now – I’m pretty proud.

The MG community is the best. You encouraged me to expand my horizons. And more importantly, I learned once again how special the members of the Classic MG Club are to each other.

Now go out and try something that you have never done!

Next month: Doc Brown’s Flux Capacitor

Lonnie Cook


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