TR4/4A Transmission “Lump” ?

[TR Tom]

I’m looking for information on the large counter weight mounted to (some?) TR 4 transmission tail shafts. My later ‘65 O.D. Equipped 4 (trans and VIN numbers are both 132802) did not have one installed when I bought it, but it was 20 years old at the time, so who knows? I found one much later at a swap meet and decided to install it, hoping it would help with the common 4 cylinder TR 3K harmonic. It didn’t seem to make any difference, but I wound up leaving it installed.

The engine and transmission are now out for a major overhaul and it got me wondering what the pros and cons of reinstalling it are.

Anyone out there know what this “lump” is supposed to accomplish, and if it actually does anything?

 

[Hamish Racing]

This has been disused before as you can imagine.
And it was as a service retro fit item for car with the 3k rpm vibration. So nt all cars suffered.

There is more discussion here

That gearbox weight....

My TR4A has one of those Fred Flintstone weights bolted on the rear of the gearbox by the drive flange. It was there when I bought the car in 1975 but since then the gearbox has been rebuilt twice, the propshaft has been replaced, the engine has a different crankshaft, a lightened flywheel and th...

www.trforums.com

 

[CJD]

+1...vibration suppression. Of note, if you have your engine, clutch and fan properly balanced, you will not have any vibration to suppress...

 

[mctriumph]

Even if you have it chromed it will NOT add anything to the car.
Balance the driveshaft!
Mad dog

 

[TR Tom]

Thanks all for the replies. Especially interesting was the link to the rather extensive trforums discussion. That verified the purpose was indeed to mitigate the 3K buzz. I know that particular harmonic is well documented and inherent to the 4cyl motors. Yes, I have balanced or replaced everything at least once over the years, and while I’ve minimized it, the buzz is still there. Not really a problem, it just bugs me I guess to know it’s there. Looks like for all the discussions, I have yet to find anyone to actually verify that the “lump” did a bit of good, so I guess I’ll be leaving it off.

I did notice that the particular one I have did not have part of the bracket (the twisted piece) but I really can’t see where that would make a difference, so again, I think it will go on the shelf.